Evoked Potential Studies

Number: 0181

Policy
Applicable CPT / HCPCS / ICD-10 Codes
Background
References

Policy

Scope of Policy

This Clinical Policy Bulletin addresses evoked potential studies.

Medical Necessity
1. Evoked Potential Studies
  
  Aetna considers evoked potential studies medically necessary for the following indications
  1. Somatosensory evoked potentials (SEPs, SSEPs) or dermatosensory evoked potentials (DSEPs)
    
    Considered medically necessary for any of the following indications:
    1. To assess any decline which may warrant emergent surgery in unconscious spinal cord injury persons who show specific structural damage to the somatosensory system, and who are candidates for emergency spinal cord surgery; or
    2. To evaluate acute anoxic encephalopathy (within 3 days of the anoxic event); or
    3. To evaluate persons with suspected brain death; or
    4. To identify clinically silent brain lesions in multiple sclerosis suspects in order to establish the diagnosis, where multiple sclerosis is suspected due to presence of suggestive neurologic symptoms plus one or more other objective findings (brain plaques on MRI, clinical lesions by history and physical examination, and/or positive CSF (determined by oligoclonal bands detected by established methods (isoelectric focusing) different from any such bands in serum, or by an increased IgG index)); or
    5. To localize the cause of a central nervous system deficit seen on exam, but not explained by lesions seen on CT or MRI; or
    6. To manage persons with spinocerebellar degeneration (e.g., Friedreichs ataxia, olivopontocerebellar (OPC) degeneration); or
    7. Unexplained myelopathy, or
    8. For Intraoperative SSEPs under certain conditions see CPB 0697 - Intraoperative Neurophysiological Monitoring.
    SEPs and DSEPs are considered experimental, investigational, or unproven for all other indications because their effectiveness for indications other than the ones listed above has not been established.
2. Visual Evoked Potentials (VEPs)
  
  Considered medically necessary for any of the following indications:
  1. To diagnose and monitor multiple sclerosis (acute or chronic phases); or
  2. To evaluate signs and symptoms of visual loss in persons who are unable to communicate (e.g., unresponsive persons, etc); or
  3. To identify persons at increased risk for developing clinically definite multiple sclerosis (CDMS); or
  4. To localize the cause of a visual field defect, not explained by lesions seen on CT or MRI, metabolic disorders, or infectious diseases.
  Standard or automated VEPs are considered experimental, investigational, or unproven for routine screening of infants and other persons; evidence-based guidelines from leading medical professional organizations and public health agencies have not recommended VEP screening of infants. VEPs are considered experimental, investigational, or unproven for all other indications because their effectiveness for indications other than the ones listed above has not been established.
3. Brain Stem Auditory Evoked Response (BAER)
  
  Footnote1** Considered medically necessary for any of the following:
  1. For intraoperative monitoring, see CPB 0697 - Intraoperative Neurophysiological Monitoring
  2. To assess brain death or profound metabolic coma in selected cases where diagnosis or outcome is unclear from standard tests (e.g., EEG); or
  3. To assess recovery of brainstem function after a lesion compressing the brainstem has been surgically removed; or
  4. To diagnose and monitor demyelinating and degenerative diseases affecting the brain stem (e.g., central pontine myelinolysis, olivopontocerebellar (OPC) degeneration, etc.); or
  5. To diagnose post-meningitic deafness in children; or
  6. To diagnose suspected acoustic neuroma; or
  7. To evaluate infants and children who have suspected hearing loss that cannot be effectively measured or monitored through audiometry; or
  8. To localize the cause of a central nervous system deficit seen on examination, but not explained by CT or MRI; or
  9. To screen infants and children under 3 years of age for hearing loss.
    
    Note: For purposes of screening (including neonatal screening), only limited auditory evoked potentials or limited evoked otoacoustic emissions (OAE) are considered medically necessary. Neonates, infants and children under 3 years of age who fail this screening test are then referred for comprehensive auditory evoked response testing or comprehensive otoacoustic emissions. Comprehensive auditory evoked response testing and comprehensive otoacoustic emissions are considered experimental, investigational, or unproven for initial screening because there is a lack of evidence of the value of comprehensive testing over the limited auditory evoked potentials or limited otoacoustic emissions for this indication.
    
    Note: Routine evoked OAE screening at a well-child visit is not considered medically necessary for children 3 years of age and younger who have passed the newborn hearing screen unless the child has a risk factor for hearing loss, has impairment of speech or auditory skills, or has an abnormal middle ear status. Evoked OAE is considered medically necessary to screen children 3 years of age and younger who did not have the initial neonatal screening and/or cannot be effectively measured or monitored through audiometry.
  BAERs are considered experimental, investigational, or unproven for all other indications (except for additional indications listed in CPB 0697 - Intraoperative Neurophysiological Monitoring) because their effectiveness for indications other than the ones listed above has not been established.
  
  Footnote1**Also known as auditory brainstem response (ABR), auditory evoked potentials (AEPs), brainstem auditory evoked potentials (BAEP), BERA, BSER, and BSRA.
4. Cervical Vestibular Evoked Myogenic Potential (cVEMP)
  
  Aetna considers cervical vestibular evoked myogenic potential (cVEMP) medically necessary for the evaluation of individuals with vertigo for semicircular canal dehiscence syndrome (SCDS) who have had a comprehensive evaluation (i.e., history, physical, audiometry, electronystagmography or videonystagmography, electrocochleography, brainstem audiometry) and the results are inconclusive.
  Aetna considers cVEMP medically necessary for evaluation of members with bilateral sensorineural hearing loss after cochlear implantation.
Experimental, Investigational, or Unproven

The following procedures are considered experimental, investigational, or unproven because the effectiveness of these approaches has not been established (not an all-inclusive list) (see CPB 0697 - Intraoperative Neurophysiological Monitoring for additional indications):
1. Auditory evoked potential for evaluation of hearing and language deficits in survivors of extracorporeal membrane oxygenation;
2. Auditory evoked potential to determine gestational age or conceptual age in pre-term neonates;
3. BAERs as a test to identify persons at increased risk for developing clinically definite multiple sclerosis (CDMS);
4. BAERs for syringomyelia and syringobulbia;
5. Cervical vestibular evoked myogenic potentials (cVEMP) for evaluation of vestibular function specifically related to the saccule/utricle;
6. cVEMP for the diagnosis of benign paroxysmal positional vertigo, and vestibular neuritis;
7. Cognitive evoked potentials (also known as auditory or visual P300 or P3 cognitive evoked potentials) to diagnose cognitive dysfunction in persons with dementia (e.g., Alzheimer's disease and Parkinson's disease) or to identify the etiology of depression in persons with chronic demyelinating disease;
8. Cortical auditory evoked response (CAER) for the diagnosis of depression, attention deficit/hyperactivity disorder, autism, or any other indication;
9. Event-related potentials for the diagnosis of attention deficit/hyperactivity disorder (see CPB 0426 - Attention Deficit/Hyperactivity Disorder) or post-traumatic stress disorder, or assessment of amyotrophic lateral sclerosis, brain injury, or evaluation of comatose persons;
10. Evoked potential studies for Kennedy's syndrome/disease;
11. Gustatory evoked potentials for diagnosing taste disorders (see CPB 0390 - Smell and Taste Disorders: Diagnosis);
12. Loudness dependence of auditory evoked potentials for monitoring of suicidal persons;
13. Measurement of evoked cortical potentials associated with transcranial magnetic stimulation;
14. Motor evoked potentials for evaluation of Wilson's disease;
15. Ocular vestibular evoked myogenic potentials (oVEMP) for the diagnosis of benign paroxysmal positioning vertigo, myasthenia gravis, or vestibular neuritis;
16. Ocular vestibular evoked myogenic potentials (oVEMP) for the evaluation of vestibular function specifically related to the saccule/utricle;
17. Olfactory event‐related potential for the evaluation of long-term COVID-19;
18. Pre-operative SSEP of the bilateral tibial somatosensory pathways prior to scoliosis surgery;
19. SEPs monitoring during trigger point injection for management of low back pain;
20. SEPs for radiculopathies and peripheral nerve lesions where standard nerve conduction velocity studies are diagnostic (see CPB 0502 - Nerve Conduction Studies);
21. SEPs for the diagnosis of carpal tunnel syndrome/ulnar nerve entrapment;
22. SEPs in conscious persons with severe spinal cord or head injuries (the standard neurologic examination is the most direct way to evaluate any deficits);
23. SEPs in diagnosis of cervical spondylytic myeloradiculopathy;
24. SEPs in the diagnosis of thoracic outlet syndrome;
25. SEPs in the diagnosis or management of acquired metabolic disorders (e.g., lead toxicity, B12 deficiency);
26. SEPs in the diagnosis or management of amyotrophic lateral sclerosis (ALS);
27. Short-latency SSEP study for evaluation of movement disorders;
28. VEPs for detecting amnestic mild cognitive impairment;
29. VEPs for evaluation and monitoring of birdshot chorioretinopathy;
30. VEPs for syringomyelia, syringobulbia, and evaluation of vigabatrin (Sabril)-associated retinal toxicity, screening Plaquenil (hydroxychloroquine) toxicity, as prognostic tests in neonates with perinatal asphyxia and hypoxic-ischemic encephalopathy;
31. Vestibular evoked myogenic potentials (VEMP) (e.g., for diagnosis of Meniere's disease or delayed endolymphatic hydrops; differentiation of Meniere disease from vestibular migraine);
32. Visual evoked potential for evaluation of neuromyelitis optica spectrum disorder.
Related Policies

Table:
CPT Codes / HCPCS Codes / ICD-10 Codes
Code	Code Description
*Somatosensory evoked potentials (SEPs, SSEPs)*:
CPT codes covered if selection criteria are met:
95925	Short-latency somatosensory evoked potential study, stimulation of any/all peripheral nerves or skin sites, recording from the central nervous system; in upper limbs
95926	in lower limbs
95927	in the trunk or head
95938	in upper and lower limbs
ICD-10 codes covered if selection criteria are met:
G11.1	Early-onset cerebellar ataxia [Friedreich's ataxia]
G23.8	Other specified degenerative diseases of basal ganglia [olivopontocerebellar (OPC) degeneration]
G35	Multiple sclerosis [with clinically silent lesions]
G36.0 - G37.9	Other demyelinating diseases of central nervous system
G93.1	Anoxic brain damage, not elsewhere classified
G93.82	Brain death
G95.9	Diseases of spinal cord [unexplained myelopathy]
ICD-10 codes not covered for indications listed in the CPB (not all-inclusive):
E53.8	Deficiency of other specified B group vitamins [diagnosis and management of acquired metabolic disorders]
F43.10 - F43.12	Posttraumatic stress disorder
E70.0 - E89.89	Metabolic disorders [diagnosis and management of acquired metabolic disorders]
F90.0 - F90.9	Attention-deficit hyperactivity disorders [ADD or ADHD]
G12.21	Amyotrophic lateral sclerosis
G12.8 - G12.9	Other and unspecified muscular atrophies
G25.81 - G25.89	Other specified extrapyramidal and movement disorders
G25.9	Extrapyramidal and movement disorder, unspecified
G54.0	Brachial plexus disorders [thoracic outlet syndrome]
G56.00 - G59	Mononeuropathies of upper and lower limbs [radiculopathies, peripheral nerve lesions, carpal tunnel syndrome/nerve entrapment]
M41.0 – M41.9	Scoliosis
M47.11 - M47.13	Cervical spondylosis with myelopathy
M50.00 - M50.13, M51.04 - M51.17	Intervertebral disc disorder with myelopathy [radiculopathies]
M50.10 - M50.13 M54.11 - M54.13	Brachial neuritis or radiculitis [where standard nerve conduction velocity studies are diagnostic]
M50.20 - M50.23 M51.24 - M51.27	Cervical disc displacement without myelopathy
M51.14 - M51.17 M54.14 - M54.17	Thoracic or lumbosacral neuritis or radiculitis, unspecified [radiculopathies]
M54.10, M54.18, M79.2	Neuralgia, neuritis, and radiculitis, unspecified
M54.30 - M54.42	Sciatica
S02.0xx+ - S02.42x+ S02.600+ - S02.92x+	Fracture of skull and facial bones [conscious]
S06.0X0A - S06.A1XS	Intracranial injury
S12.000+ - S12.9xx+ S22.000+ - S22.089+ S32.000+ - S32.2xx+	Fracture of vertebral column [conscious]
S14.0xx+ - S14.159+ S24.0xx+ - S24.159+ S34.01x+ - S34.139+	Spinal cord injury [conscious]
T37.8x1+ - T37.8x4+	Poisoning by other specified systemic anti-infectives
T56.0x1+ - T56.0x4+	Toxic effect of lead and its compounds (including fumes)
Z13.850 - Z13.858	Encounter for screening for nervous system disorders [indicates routine exam without signs or symptoms when reported alone]
Z13.88	Encounter for screening for disorder due to exposure to contaminants [indicates routine exam without signs or symptoms when reported alone]
*Visual evoked potentials (VEPs)*:
CPT codes covered if selection criteria are met:
95930	Visual evoked potential (VEP) testing central nervous system, checkerboard or flash
CPT codes not covered for indications listed in the CPB:
0333T	Visual evoked potential, screening of visual acuity, automated [not covered for screening]
ICD-10 codes covered if selection criteria are met (for members > 3 mos of age):
A39.82	Meningococcal retrobulbar neuritis
A52.10 - A52.19	Symptomatic neurosyphilis
A69.20	Lyme disease, unspecified
A83.0 - A84.9 A85.2	Mosquito-borne viral encephalitis, tick-borne viral encephalitis, and viral encephalitis transmitted by other and unspecified arthropods
B00.4	Herpesviral encephalitis
B05.0	Measles complicated by encephalitis
B06.01	Rubella encephalitis
B10.01	Human herpesvirus 6 encephalitis
B10.09	Other human herpesvirus encephalitis
C70.0 - C70.9 C72.0 - C72.9	Malignant neoplasm of other and unspecified parts of nervous system
C79.31, C79.49	Secondary malignant neoplasm of brain and spinal cord
D32.0 - D33.9	Benign neoplasm of brain and other parts of nervous system
D42.0 - D43.9	Neoplasm of uncertain behavior of brain and spinal cord, meninges, and other and unspecified parts of nervous system
D44.3 - D44.5	Neoplasm of uncertain behavior of endocrine glands [pituitary gland, craniopharyngeal duct, pineal gland]
D49.6	Neoplasm of unspecified behavior of brain
F44.4 - F44.7 F44.89 - F44.9	Conversion disorder
G11.0 - G11.9	Hereditary ataxia
G23.0 - G23.9	Other degenerative diseases of the basal ganglia
G35	Multiple sclerosis
G36.0 - G37.9	Other demyelinating diseases of central nervous system
G45.0 -G45.2 G45.8 - G45.9	Transient cerebral ischemic attacks and related syndromes
G50.0 - G70.9	Trigeminal, facial, and other cranial nerve disorders, nerve root and plexus disorders, mononeuritis, neuropathy, and myoneural disorders
G80.0 - G80.9	Cerebral palsy
G81.00 - G81.94	Hemiplegia and hemiparesis
G93.1	Anoxic brain damage, not elsewhere classified
G93.2	Benign intracranial hypertension
G93.5	Compression of brain
G93.6	Cerebral edema
H47.011 - H47.9	Disorders of the optic nerve and visual pathways
H53.001 - H53.9	Visual disturbances
H81.01 - H83.2x9	Disorders of vestibular function
H83.3 - H94.83	Other disorders of ear and hearing loss
I60.00 - I66.9	Subarachnoid hemorrhage, intracerebral hemorrhage, other and unspecified intracranial hemorrhage, occlusion and stenosis of precerebral arteries, and occlusion of cerebral arteries
I67.1	Cerebral aneurysm, nonruptured
Q85.00 - Q85.09	Neurofibromatosis (nonmalignant)
R26.0 - R27.9 R29.5	Abnormality of gait, lack of coordination, and transient paralysis of limb
R40.20 - R40.236	Coma [unresponsive]
R40.3	Persistent vegetative state [unresponsive, unable to communicate]
R42	Dizziness and giddiness
R47.01	Aphasia [unable to communicate]
R94.110 - R94.138	Nonspecific abnormal results of function studies of peripheral nervous system and special senses
S04.011+ - S04.9	Injury to optic nerve and pathways
S04.011s-S04.9 S14.0xxs-S14.9xxs S24.0xxs-S24.9xxs S34.01xs-S34.9xxs S44.00xs-S44.92xs S54.00xs-S54.92xs S64.00xs-S64.92xs S74.00xs-S74.92xs S84.00xs-S84.92xs S94.00xs-S94.92xs	Injury to cranial nerve, spinal cord, nerve root(s), spinal plexus(es), and other nerves of trunk, peripheral nerve of shoulder girdle and upper limb, or peripheral nerve of pelvic girdle and lower limb, sequela
S06.0x6+	Concussion with prolonged loss of consciousness without return to pre-existing conscious level
ICD-10 codes not covered for indications listed in the CPB (for members > 3 mos of age) (not all-inclusive):
B50.0 - B54	Malaria
E22.0 - E23.7	Hyperfunction, hypofunction and other disorders of the pituitary gland
F01.50 - F03.91, F05	Dementia and delirium
F10.27	Alcohol dependence with alcohol-induced persisting dementia
F10.97, F11.22, F13.27, F18.17 F18.27, F18.97, F19.17, F19.27 F19.97	Drug induced persisting dementia
F90.0 - F90.9	Attention-deficit hyperactivity disorder
G20.A1 - G20.9	Parkinson's disease
G30.0 - G30.9	Alzheimer's disease
G31.84	Mild cognitive impairment, so stated [amnestic]
G36.0	Neuromyelitis optica
G95.0	Syringomyelia and syringobulbia
H30.90 - H30.93	Unspecified chorioretinal inflammation [birdshot chorioretinopathy]
L93.0 - L93.2	Lupus erythematosus
M32.0- M32.9	Systemic lupus erythematosus
O98.611 - O98.63	Protozoal diseases complicating pregnancy, childbirth and the puerperium [malaria]
P35.0 - P35.9	Congenital viral disease [specific to the perinatal period]
T37.2X1+ - T37.2X6+	Poisoning by antimalarials and drugs acting on other blood protozoa
ICD-10 codes not covered for indications listed in the CPB (for members < 3 mos of age/ neonatal screen):
B50.0 - B54	Malaria
E22.0 - E23.7	Hyperfunction, hypofunction and other disorders of the pituitary gland
G40.201 - G40.219	Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable or not intractable, with and without status epilepticus
G95	Syringomyelia and syringobulbia
L93.0 - L93.2	Lupus erythematosus
M32.0- M32.9	Systemic lupus erythematosus
P00.0 - P96.9	Certain conditions originating in the perinatal period
P19.0 - P19.9	Metabolic acidemia in newborn
P84	Other problems with newborn [birth asphyxia]
P91.60 - P91.63	Hypoxic ischemic encephalopathy [HIE]
T37.2X1+ - T37.2X6+	Poisoning by antimalarials and drugs acting on other blood protozoa
Z00.110	Health examination for newborn under 8 days old
Z00.121 - Z00.129	Encounter for routine child health examination with or without abnormal findings
Z01.00 - Z01.01	Encounter for examination of eyes and vision [indicates routine screen without signs or symptoms when reported alone]
Z13.5	Encounter for screening for eye and ear disorders [indicates routine screen without signs or symptoms when reported alone]
Z13.858	Encounter for screening for other nervous system disorders
Z37.0 - Z37.9	Outcome of delivery
Z38.00 - Z38.8	Liveborn infants according to place of birth and type of delivery
*Brain stem auditory evoked response (BAER), comprehensive*:
CPT codes covered if selection criteria are met:
92652	Auditory evoked potentials; for threshold estimation at multiple frequencies, with interpretation and report
92653	Auditory evoked potentials; neurodiagnostic, with interpretation and report
ICD-10 codes covered if selection criteria are met (members > 3 mos of age):
A39.82	Meningococcal retrobulbar neuritis
A52.10 - A5219	Symptomatic neurosyphilis
A69.20	Lyme disease, unspecified
A81.2	Progressive multifocal leukoencephalopathy
A83.0 - A84.9, A85.2	Mosquito-borne viral encephalitis, tick-borne viral encephalitis, and viral encephalitis transmitted by other and unspecified arthropods
B00.4	Herpesviral encephalitis
B05.0	Measles complicated by encephalitis
B06.01	Rubella encephalitis
B10.01	Human herpesvirus 6 encephalitis
B10.09	Other human herpesvirus encephalitis
C70.0 - C70.9 C72.0 - C72.9	Malignant neoplasm of other and unspecified parts of the nervous system
C71.0 - C71.9	Malignant neoplasm of brain
C79.31, C79.49	Secondary malignant neoplasm of brain and spinal cord
D32.0 - D33.9	Benign neoplasm of brain and other parts of nervous system
D42.0 - D43.9	Neoplasm of uncertain behavior of brain and spinal cord, meninges, and other and unspecified parts of nervous system
D44.3 - D44.5	Neoplasm of uncertain behavior of endocrine glands [pituitary gland, craniopharyngeal duct, pineal gland]
D49.6	Neoplasms of unspecified behavior of brain
F44.4 - F44.7 F44.89 - F44.9	Conversion disorder
G09	Sequelae of inflammatory disease of central nervous system
G11.0 - G11.9	Hereditary ataxia
G23.0 - G23.9	Other degenerative disease of basal ganglia
G35	Multiple Sclerosis
G36.0 - G37.9	Other demyelinating diseases of the central nervous system
G45.0 - G45.2 G45.8 - G45.9	Transient cerebral ischemic attacks and related syndromes
G50.0 - G70.9	Trigeminal, facial, and other cranial nerve disorders, nerve root and plexus disorders, mononeuritis, neuropathy, and myoneural disorders
G80.0 - G80.9	Cerebral palsy
G81.00 - G81.94	Hemiplegia and hemiparesis
G93.0	Cerebral cysts
G93.1	Anoxic brain damage, not elsewhere classified
G93.2	Benign intracranial hypertension
G93.5	Compression of brain
G93.6	Cerebral edema
G93.82	Brain death [for members >3 months of age]
H47.011 - H47.9	Disorders of the optic nerve and visual pathways
H53.001 - H53.9	Visual disturbances
H81.01 - H83.2x9	Disorders of vestibular function
H83.3 - H94.83	Other disorders of ear and hearing loss
I60.00 - I66.9	Subarachnoid hemorrhage, intracerebral hemorrhage, other and unspecified intracranial hemorrhage, occlusion and stenosis of precerebral arteries, occlusion of cerebral arteries
I67.1	Cerebral aneurysm, nonruptured
I67.4	Hypertensive encephalopathy
I67.81 - I67.82 I67.89	Acute cerebrovascular insufficiency, cerebral ischemia and other cerebrovascular disease
I67.841 - I67.848	Cerebral vasospasm and vasoconstriction
P03.0 - P03.9	Newborn (suspected to be) affected by other complications of labor and delivery
P91.0 - P91.1 P91.3 - P91.5	Other disturbances of cerebral status of newborn
Q01.0 - Q01.9	Encephalocele
Q04.0 - Q04.3	Congenital reduction deformities of brain
Q07.00 - Q07.03	Arnold-Chiari syndrome
R26.0 - R27.9, R29.5	Abnormality of gait, lack of coordination, and transient paralysis of limb
R40.20 - R40.236	Coma
R40.3	Persistent vegetative state
R42	Dizziness and giddiness
R94.110 - R94.138	Nonspecific abnormal results of function studies of peripheral nervous system and special senses
S04.011+ - S04.9	Injury to optic nerve and pathways
S04.011s-S04.9 S14.0xxs-S14.9xxs S24.0xxs-S24.9xxs S34.01xs-S34.9xxs S44.00xs-S44.92xs S54.00xs-S54.92xs S64.00xs-S64.92xs S74.00xs-S74.92xs S84.00xs-S84.92xs S94.00xs-S94.92xs	Injury to cranial nerve, spinal cord, nerve root(s), spinal plexus(es), and other nerves of trunk, peripheral nerve of shoulder girdle and upper limb, or peripheral nerve of pelvic girdle and lower limb, sequela
S06.0x6+	Concussion with prolonged loss of consciousness without return to pre-existing conscious level
Z01.110	Encounter for hearing examination following failed hearing screening
Z01.118	Encounter for examination of ears and hearing with other abnormal findings
Z76.1 - Z76.2	Encounter for health supervision of foundling and other healthy infant or child
Z79.2	Long-term (current) use of antibiotics [damage due to ototoxic drugs]
Z79.891 - Z79.899	Long-term (current) use of opiate analgesic and other drug therapy [damage due to ototoxic drugs]
ICD-10 codes not covered for indications listed in the CPB (members > 3 mos of age) (not all-inclusive):
F01.50 - F03.91, F05	Dementia and delirium
F02.80 - F02.81	Dementia in other diseases classified elsewhere with or without behavioral disturbance
F06.8	Other specified mental disorders due to known physiological condition
F10.27	Alcohol dependence with alcohol-induced persisting dementia
F10.97, F11.22, F13.27, F18.17 F18.27, F18.97, F19.17, F19.27 F19.97	Drug induced persisting dementia
F20.2	Catatonic schizophrenic
F20.9	Schizophrenia, unspecified
F30.10 - F33.9	Episodic mood disorders
F34.1	Dysthymic disorder
F43.10 - F43.12	Posttraumatic stress disorder
F84.0	Autistic disorder
F90.0 - 90.9	Attention-deficit hyperactivity disorder
G12.8 - G12.9	Other and unspecified muscular atrophies [Kennedy's syndrome]
G20 - G21.9	Parkinson's disease
G30.0 - G30.9	Alzheimer's disease
G31.01	Pick's disease
G31.09	Other frontotemporal dementia
G31.83	Dementia with Lewy bodies
G95.0	Syringomyelia and syringobulbia
P00.2 - P00.3 P00.89 - P00.9	Newborn (suspected to be) affected by maternal conditions that may be unrelated to present pregnancy
R43.0 - R43.9	Disturbances of smell and taste
T14.90xA - T14.91xS	Suicide attempt
U07.1	COVID-19
Z00.2 - Z00.3, Z00.8	Constitutional states in development
Z13.5	Encounter screening for ear disease [indicates routine exam without signs or symptoms when reported alone]
Z37.0 - Z37.69	Outcome of delivery
Z38.00 - Z38.8	Liveborn infants according to place of birth and type of delivery
Z76.1	Encounter for health supervision and care of foundling
Z76.2	Encounter for health supervision and care of other healthy infant and child
ICD-10 codes not covered for indications listed in the CPB (for members < 3 mos of age/ neonatal screen):
G95.0	Syringomyelia and syringobulbia
P00.0 - P96.9	Certain conditions originating in the perinatal period
U07.1	COVID-19
Z00.2 - Z00.3, Z00.8 Z76.1 - Z76.2	Health supervision of infant or child or constitutional states of development [neonatal screen]
Z13.5	Encounter for screening for ear diseases [indicates routine exam without signs or symptoms when reported alone]
Z37.0 - Z37.9	Outcome of delivery
Z38.00 - Z38.8	Liveborn infants according to place of birth and type of delivery
*Brain stem auditory evoked response (BAER), limited*:
CPT codes covered if selection criteria are met:
92650	Auditory evoked potentials; screening of auditory potential with broadband stimuli, automated analysis
92651	Auditory evoked potentials; for hearing status determination, broadband stimuli, with interpretation and report
ICD-10 codes covered if selection criteria are met:
A39.82	Meningococcal retrobulbar neuritis
A52.10 - A52.19	Symptomatic neurosyphilis
A69.20	Lyme disease, unspecified
A83.0 - A84.9, A85.2	Mosquito-borne viral encephalitis, tick-borne viral encephalitis, and viral encephalitis transmitted by other and unspecified arthropods
B00.4	Herpesviral encephalitis
B05.0	Measles complicated by encephalitis
B06.01	Rubella encephalitis
B10.01	Human herpesvirus 6 encephalitis
B10.09	Other human herpesvirus encephalitis
C70.0 - C70.9 C72.0 - C72.9	Malignant neoplasm of other and unspecified parts of the nervous system
C71.0 - C71.9	Malignant neoplasm of brain
D32.0 - D33.9	Benign neoplasm of brain and other parts of the nervous system
D42.0 - D43.9	Neoplasm of uncertain behavior of brain and spinal cord, meninges, and other and unspecified parts of nervous system
D44.3 - D44.5	Neoplasm of uncertain behavior of endocrine glands [pituitary gland, craniopharyngeal duct, pineal gland]
D49.6	Neoplasms of unspecified behavior of brain
F44.4 - F44.7	Conversion disorder
G09	Sequelae of inflammatory disease of central nervous system
G11.0 - G11.9	Hereditary ataxia
G23.0 - G23.9	Other degenerative disease of basal ganglia
G36.0 - G37.9	Other demyelinating diseases of the central nervous system
G45.0 - G45.2, G45.8 - G45.9	Transient cerebral ischemic attacks and related syndromes
G50.0 - G70.9	Trigeminal, facial, and other cranial nerve disorders, nerve root and plexus disorders, mononeuritis, neuropathy, and myoneural disorders
G80.0 - G80.9	Cerebral palsy
G81.00 - G81.94	Hemiplegia and hemiparesis
G93.0	Cerebral cysts
G93.1	Anoxic brain damage, not elsewhere classified
G93.2	Benign intracranial hypertension
G93.5	Compression of brain
G93.6	Cerebral edema
H53.001 - H53.9	Visual disturbances
H83.3 - H94.83	Other disorders of ears and hearing loss
I60.00 - I66.9	Subarachnoid hemorrhage, intracerebral hemorrhage, other and unspecified intracranial hemorrhage, occlusion and stenosis of precerebral arteries, occlusion of cerebral arteries
I67.1	Cerebral aneurysm, nonruptured
I67.4	Hypertensive encephalopathy
I67.81 - I67.89	Other specified cerebrovascular diseases
Numerous options	Injury to cranial nerve, spinal cord, nerve root(s), spinal plexus(es), and other nerves of trunk, peripheral nerve of shoulder girdle and upper limb, or peripheral nerve of pelvic girdle and lower limb, sequela
P00.2 - P00.3 P00.89 - P00.9	Newborn (suspected to be) affected by maternal conditions that may be unrelated to present pregnancy
P03.0 - P03.9	Newborn (suspected to be) affected by other complications of labor and delivery
P91.0 - P91.1 P91.3 - P91.5	Other disturbances of cerebral status of newborn
Q01.00 - Q01.9	Encephalocele
Q04.0 - Q04.3	Congenital reduction deformities of brain
Q07.00 - Q07.03	Arnold-Chiari Syndrome
R26.0 - R27.9, R29.5	Abnormality of gait, lack of coordination, and transient paralysis of limb
R40.20 - R40.236	Coma
R40.3	Persistent vegetative state
R42	Dizziness and giddiness
R94.110 - R94.138	Nonspecific abnormal results of function studies of peripheral nervous system and special senses
S04.011+ - S04.9	Injury to optic nerve and pathways
S06.0x6+	Concussion with prolonged loss of consciousness without return to pre-existing conscious level
Z00.110	Health examination for newborn under 8 days old
Z00.111	Health examination for newborn under 8 to 28 days old
Z00.121 - Z00.129	Encounter for routine child health examination with/without abnormal findings [over 28 days]
Z01.10	Encounter for examination of ears and hearing without abnormal findings
Z01.110	Encounter for hearing examination following failed hearing screening
Z37.0 - Z37.9	Outcome of delivery
Z38.00 - Z38.8	Liveborn infants according to place of birth and type of delivery
Z76.2	Encounter for health supervision and care of other healthy infant and child
Z79.2	Long-term (current) use of antibiotics [damage due to ototoxic drugs]
Z79.891 - Z79.899	Long-term (current) use of opiate and other drug therapy [damage due to ototoxic drugs]
ICD-10 codes not covered for indications listed in the CPB:
G12.8 - G12.9	Other and unspecified muscular atrophies [Kennedy's syndrome]
G95.0	Syringomyelia and syringobulbia
T14.90xA - T14.91xS	Suicide attempt
U07.1	COVID-19
*Cervical vestibular myogenic potential (cVEMP)*:
CPT codes covered if selection criteria are met:
92517	Vestibular evoked myogenic potential (VEMP) testing, with interpretation and report; cervical (cVEMP)
92519	Vestibular evoked myogenic potential (VEMP) testing, with interpretation and report; cervical (cVEMP) and ocular (oVEMP)
ICD-10 codes covered if selection criteria are met:
H83.8X1 – H83.8X9	Other specified diseases of inner ear [semicircular canal dehiscence syndrome (SCDS)]
H90.3	Conductive hearing loss, unspecified
Z96.21	Cochlear implant status
*Evoked otoacoustic emissions*:
CPT codes covered if selection criteria are met:
92558	Evoked otoacoustic emissions, screening (qualitative measurement of distortion product or transient evoked otoacoustic emissions), automated analysis
92587	Evoked otoacoustic emissions; limited (single stimulus level, either transient or distortion products)
92588	comprehensive or diagnostic evaluation (comparison of transient and/or distortion product otoacoustic emissions at multiple levels and frequencies [not covered for routine screening of neonates]
ICD-10 codes not covered for indications listed in the CPB (for comprehensive exam only for members < 3 mos. of age/ neonatal screen):
P00.0 - P96.9	Certain conditions originating in the perinatal period
Z00.2 - Z00.3, Z00.8 Z76.1 - Z76.2	Health supervision of infant or child or constitutional states of development [neonatal screen]
Z01.10	Encounter for examination of ears and hearing without abnormal findings
Z13.5	Encounter for screening for ear diseases [indicates routine exam without signs or symptoms when reported alone]
Z37.0 - Z37.9	Outcome of delivery
Z38.00 - Z38.8	Liveborn infants according to place of birth and type of delivery
Z76.1	Encounter for health supervision and care of foundling
Z76.2	Encounter for health supervision and care of other healthy infant and child
*ICD-10 codes covered for indications listed in the CPB not all inclusive (for screening exam only for members < 3 yrs. of age)*:
F80.0 - F80.9	Specific developmental disorders of speech and language
R94.120 - R94.128	Abnormal results of function studies of ear and other special senses
Z01.110	Encounter for hearing examination following failed hearing screening
Z01.118	Encounter for examination of ears and hearing with other abnormal findings
ICD-10 codes not covered for indications listed in the CPB (for screening exam only for members < 3 yrs. of age):
Z00.121 - Z00.129	Encounter for routine child health examination with/without abnormal findings
*Motor evoked potentials (other than intraoperative with SSEPs)*:
CPT codes not covered for indications listed in the CPB:
95928	Central motor evoked potential study (transcranial motor stimulation); upper limbs
95929	lower limbs
95939	Central motor evoked potential study (transcranial motor stimulation); in upper and lower limbs
ICD-10 codes not covered for indications listed in the CPB:
E83.01	Wilson's disease
Vestibular evoked myogenic potentials (VEMP):
CPT codes not covered for indications listed in the CPB:
92517	Vestibular evoked myogenic potential (VEMP) testing, with interpretation and report; cervical (cVEMP)
92518	ocular (oVEMP)
92519	cervical (cVEMP) and ocular (oVEMP)
ICD-10 codes not covered for indications listed in the CPB:
G43.801 - G43.819	Other migraine [vestibular migraine]
H81.01 - H81.09	Meniere's disease.
H81.10 - H81.13	Benign paroxysmal vertigo.
H81.20 - H81.23	Vestibular neuronitis
*Evoked cortical potentials associated with transcranial magnetic stimulation*:
CPT codes not covered for indications listed in the CPB:
0858T	Externally applied transcranial magnetic stimulation with concomitant measurement of evoked cortical potentials with automated report

Background

Evoked potentials measure conduction velocities of sensory pathways in the central nervous system using computerized averaging techniques. Three types of evoked potentials are routinely performed:

somatosensory;
visual; and
brainstem auditory.

In each of these tests a peripheral sense organ is electrically stimulated and conduction velocities are recorded for central somatosensory pathways located in the posterior columns of the spinal cord, brain stem, and thalamus, and the primary sensory cortex located in the parietal lobes.

Somatosensory evoked potentials (SEPs or SSEPs) (also known as cerebral sensory evoked potentials) augment the sensory examination and are most useful in assessing the spinal nerve roots, spinal cord, or brain stem for evidence of delayed nerve conduction. Dermatomal somatosensory evoked potentials (DSEPs) are elicited by stimulating the skin "signature" areas of specific nerve roots. Both techniques involve production and recording of small electrophysiological responses of the central nervous system that follow sequential electrical stimulation of peripheral nerves. These small electrophysiological responses are extracted from the background noise of electroencephalography (EEG), usually by signal averaging techniques. Delays in signal propagation suggest lesions of the central sensory pathways. Although controversial, evoked potentials have been used to assess the prognosis of children with spinal cord lesions, brain malformations, and neurodegenerative diseases, as well as young children who are at risk for brain injury, such as preterm infants. Somatosensory evoked potentials measurements have been used to predict outcome in spinal cord injury; however, signal changes on MRI actually may be more useful in determining the severity of injury. Hemorrhage within the spinal cord is readily identified on MRI, and such hemorrhage is predictive of injury severity. Intra-operative SSEP measurements are useful in complex neurologic, orthopedic, and vascular surgical procedures as a means of gauging nerve injury during surgery (e.g., resection of cord tumors).

Somatosensory evoked potentials are altered by conditions that affect the somatosensory pathways, including both focal lesions (such as strokes, tumors, cervical spondylosis, syringomyelia) and diffuse diseases (such as hereditary systemic neurologic degeneration, subacute combined degeneration, and vitamin E deficiencies).

Somatosensory evoked potentials may detect clinically silent brain lesions in multiple sclerosis suspects. Although SEP abnormalities alone are insufficient to establish the diagnosis of multiple sclerosis, the diagnosis can be established when there is also other objective findings (brain plaques on MRI, clinical lesions by history and physical examination, and/or positive CSF (determined by oligoclonal bands detected by established methods (isoelectric focusing) different from any such bands in serum, or by an increased IgG index)).

Fifty to 60 % of multiple sclerosis patients have other concurrent demyelinating lesions that may not be clinically evident, and SSEP may be helpful in documenting these abnormalities. Somatosensory evoked potentials abnormalities are also produced by other diseases affecting myelin (adrenoleukodystrophy and adrenomyelo-neuropathy, metachromatic leukodystrophy, Pelizaeus-Merzbacher disease). In adrenoleukodystrophy and adrenomyeloneuropathy, SSEP abnormalities may be present in asymptomatic heterozygotes. Abnormally large amplitude SEPs, reflecting enhanced cortical excitability, are seen in progressive myoclonus epilepsy, in some patients with photosensitive epilepsy, and in late infantile ceroid lipofuscinosis.

Studies have demonstrated a statistically significant association between abnormal visual evoked potentials (VEPs) and an increased risk of developing clinically definite multiple sclerosis (CDMS). In these studies, patients with suspected MS were 2.5 to 9 times as likely to develop CDMS as patients with normal VEPs. Visual evoked potentials sensitivities ranged from 25 % to 83 %. Visual evoked potentials improved the ability to predict which MS suspects will develop CDMS by as much as 29 %.

Measurement of visual evoked responses (VERs) is the primary means of objectively testing vision in infants and young children suspected of having disorders of the visual system, where the child is too young to report differences in color vision or to undergo assessment of visual fields and visual acuity. A flashing stroboscope or an alternating checkerboard pattern is presented and the wave patterns are recorded. In an infant, vision may be reliably tested using a flashing light during quiet sleep. Lesions affecting the visual pathways can be localized by noting the presence of decreased amplitudes or increased latencies of VERs, and by determining whether VER abnormalities involve one or both eyes. Visual evoked responses are also useful for testing vision in other persons who are not able to communicate.

Brain stem auditory evoked responses (BAERs) are electrical potentials that are produced in response to an auditory stimulus and are recorded from disk electrodes attached to the scalp. Depending on the amount of time elapsed between the "click" stimulus and the auditory evoked response, potentials are classified as early (0 to 10 msec), middle (11 to 50 msec), or late (51 to 500 msec). The early potentials reflect electrical activity at the cochlea, 8th cranial nerve, and brain stem levels; the latter potentials reflect cortical activity. In order to separate evoked potentials from background noise, a computer averages the auditory evoked responses to 1,000 to 2,000 clicks. Early evoked responses may be analyzed to estimate the magnitude of hearing loss and to differentiate among cochlea, 8th nerve, and brainstem lesions.

The clinical utility of BAER over standard auditory testing is due to several of BAER's characteristics:

BAER's resistance to alteration by systemic metabolic abnormalities, medications or pronounced changes in the state of consciousness of the patient; and
the close association of BAER waveform abnormalities to underlying structural pathology.

Brain stem auditory evoked responses have been proven effective for differentiating conductive from sensory hearing loss, for detecting tumors and other disease states affecting central auditory pathways (e.g., acoustic neuromas), and for noninvasively detecting hearing loss in patients who can not cooperate with subjective auditory testing (e.g., infants, comatose patients). BAER is the test of choice to assess hearing in infants and young children. It is most useful for following asphyxia, hyperbilirubinemia, intracranial hemorrhage, or meningoencephalitis or for assessing an infant who has trisomy. BAER also is useful in the assessment of multiple sclerosis or other demyelinating conditions, coma, or hysteria. Audiometric analysis using multiple sound frequencies is usually preferred over BAER for testing hearing in cooperative patients who are able to report when sounds are heard. Evidence is insufficient at this time to recommend BAER as a useful test to identify patients at increased risk for developing CDMS.

Studies of cognitive evoked potentials (also known as the P300 or P3 cognitive evoked potentials) have been used in research settings to correlate changes in cognitive evoked potentials with clinical changes in cognitive function in patients with dementia (e.g., Alzheimer's disease and Parkinson's disease) and identify the etiology of depression in patients with chronic demyelinating disease. However, there is insufficient evidence regarding the effectiveness of cognitive evoked potential studies in diagnosing or rendering treatment decisions that would affect health outcomes. Furthermore, there is a lack of studies comparing cognitive evoked potential studies with standard neuropsychiatric and psychometric tests used in diagnosing cognitive dysfunction.

The American Academy of Pediatrics (AAP) Task Force on Newborn and Infant Hearing and the Joint Committee on Infant Hearing (JCIH) endorse the implementation of universal newborn hearing screening. Screening should be conducted before discharge from the hospital whenever possible. Physicians should provide recommended hearing screening, not only during early infancy but also through early childhood for those children at risk for hearing loss (e.g., history of trauma, meningitis) and for those demonstrating clinical signs of possible hearing loss.

Prior to July 2008, the U.S. Preventive Services Task Force (USPSTF) recommended screening for hearing loss in all newborn infants, stating that all infants should be screened before 1 month of age. Those infants who do not pass the newborn screening should undergo audiologic and medical evaluation before 3 months of age for confirmatory testing. Because of the elevated risk of hearing loss in infants with risk indicators (e.g., neonatal intensive care unit admission for 2 or more days; syndromes associated with hearing loss, such as Usher syndrome and Waardenburg syndrome; family history of hereditary childhood hearing loss; craniofacial abnormalities; and congenital infections such as cytomegalovirus, toxoplasmosis, bacterial meningitis, syphilis, herpes, and rubella), an expert panel recommends that these children undergo periodic monitoring for 3 years. The USPSTF found good evidence that newborn hearing screening leads to earlier identification and treatment of infants with hearing loss and improves language outcomes. However, additional studies detailing the correlation between childhood language scores and functional outcomes (e.g., school attainment and social functioning) are needed. In July 2008, the USPSTF inactivated its recommendation on "Hearing loss in newborns: Screening". The USPSTF has decided not to review the evidence and update its recommendations, and that the previous evidence review and recommendation may contain information that is outdated.

"Universal screening for hearing loss is preferred because targeted selective screening for only at-risk infants would fail to identify 50 to 75 percent of all cases of moderate to profound bilateral hearing loss. As a result, hearing loss in a substantial number of hearing-impaired neonates would be delayed with only selective screening. All states in the United States have implemented universal newborn hearing screening (UNHS) programs and most states have laws mandating UNHS. Clinicians should be familiar with their state laws" (Vohr, 2018).

Two types of UNHS tests are commonly used to screen for congenital hearing loss:

otoacoustic emissions (OAEs) and
auditory brainstem response (ABR) (Helfand et al, 2001).

Otoacoustic emissions testing evaluates the integrity of the inner ear (cochlea). In response to noise, vibrations of the hair cells in a healthy inner ear generate electrical responses, known as otoacoustic emissions. The absence of OAEs indicates that the inner ear is not responding appropriately to sound. Transient evoked otoacoustic emissions (TEOAEs) are generated in response to wide-band clicks, while distortion product otoacoustic emissions (DPOAE) are a response to tones. Both stimuli are presented via a light-weight ear canal probe. A microphone picks up the signal, and multiple responses are averaged to get a specific repeatable waveform. Otoacoustic emissions are used in screening and diagnosis of hearing impairments in infants, and in young children and patients with cognitive impairments (e.g., mental retardation, dementia) who are unable to respond reliably to standard hearing tests. Otoacoustic emissions are also useful for evaluating patients with tinnitus, suspected malingering, and for monitoring cochlear damage from ototoxic drugs.

The ABR is an electrophysiological response generated in the brainstem in response to auditory signals and composed of either clicks or tones. The stimulus is delivered via earphones or an inserted ear probe, and scalp electrodes pick up the signal. Auditory brainstem response evaluates the integrity of the peripheral auditory system and the auditory nerve pathways up to the brainstem and is able to identify infants with normal cochlear function but abnormal 8th-nerve function (auditory neuropathy). For purposes of neonatal screening, a limited ABR is performed in the nursery using a significantly low intensity level (35 to 40 dB) to rule out marked hearing loss (Schwartz and Schwartz, 1990; Scott and Bhattacharyya, 2002). If testing at this level fails to elicit a response, the infant is referred to an audiologic laboratory for a comprehensive ABR, involving testing at many different intensity levels.

Typically, screening programs use a 2-stage screening approach (either OAE repeated twice, OAE followed by ABR, or ABR repeated twice). Criteria for defining a "pass" or "fail" on the initial screening test vary widely. Comprehensive (diagnostic) OAEs or ABRs are used to diagnose hearing impairments identified by limited (screening) tests.

Auditory brainstem response and OAE have limitations that affect their accuracy in certain patients. Both require a sleeping or quiet child. Middle-ear effusion or debris in the external canal can compromise the accuracy of these tests. Otoacoustic emissions and ABR test the peripheral auditory system and 8th nerve pathway to the brainstem, respectively. They are not designed to identify infants with central hearing deficits. Therefore, infants with risk factors for central hearing deficits, particularly those who have congenital Cytomegalovirus infection or prolonged severe hypoxia at birth, may pass their newborn hearing screens with either OAE or ABR, but develop profound hearing loss in early infancy.

The newer generation of automated screeners are easy to use and do not require highly trained staff. However, equipping hospitals with equipment and sufficient staff can be costly, the staff must be trained to understand the limitations of the techniques, and ongoing quality control is essential to achieve accurate, consistent test results. The importance of technique is illustrated by the results of multicenter studies of universal screening, in which the rates of false positive and technically inadequate examinations varied 10-fold among sites.

There are differences between the guidelines with respect to the screening technology that is endorsed. The Joint Committee on Infant Hearing recommends that all infants have access to screening using a physiologic measure (either otoacoustic emissions [TEOAE or DPOAE] and/or ABR). The AAPstates that although additional research is necessary to determine which screening test is ideal, EOAE and/or ABR are presently the screening methods of choice. The AAP defers recommending a preferred screening test. The USPSTF recommends a 1- or 2-step validated protocol, stating that OAEs followed by ABR in those who failed the first test is a frequently used protocol. Well-maintained equipment, thoroughly trained staff, and quality control programs are also recommended to avoid false-positive tests.

The American Academy of Audiology on "Childhood hearing screening guidelines" (2011) recommends OAE use only for preschool and school age children for whom pure tone screening is not developmentally appropriate (ability levels less than 3 years of age).

UpToDate review on "Screening the newborn for hearing loss" (Vohr, 2018) states that with the adoption of universal newborn hearing screening (UNHS), the age at identification of hearing loss has decreased from a range of 24 to 30 months to 2 to 3 months of age. For infants who passed the initial hearing screen, follow-up consists of continued routine monitoring of language acquisition, auditory skills, middle ear status, and attention to parental concerns. "Additional oversight and testing are reserved for term infants who failed OAE but passed AABR, NICU graduates, and infants with risk factors for hearing loss who passed newborn screen".

It is recommended that infants who fail the initial hearing screen have additional audiologic evaluation by three months of age (Vohr, 2018).

Cortical auditory evoked responses (CAERs) measure the later-occurring auditory evoked potentials reflecting cortical activity in response to an auditory stimulus (UBC, 2005). Cortical auditory evoked responses have a long latency, compared to the short latency auditory evoked responses; they have been used in clinical research to evaluate the timing, sequence, strength, and anatomic location of brain processes involved with the perception of sounds. Current research underway concerns the use of CAERs to understand the brain processes underlying basic hearing percepts such as loudness, pitch, and localisation, as well as those processes involved with speech perception (UBC, 2005).

Vestibular evoked myogenic potentials (VEMP), also known as click evoked neurogenic vestibular potentials, are presumed to originate in the saccule. They are recorded from surface electrodes over the sternocleidomastoid muscles, and can be activated by means of brief, high-intensity acoustic stimuli. Papathanasiou et al (2003) stated that VEMP testing is a possible new diagnostic technique that may be specific for the vestibular pathway. It has potential use in patients with symptoms of dizziness, sub-clinical symptoms in multiple sclerosis, and in disorders specific for the vestibular nerve. There is a lack of reliable evidence from well controlled, prospective studies demonstrating that VEMP testing alters management such that clinical outcomes are improved. Current evidence-based guidelines on the management of neurological disorders from leading medical professional organizations have not incorporated VEMP testing in diagnostic and treatment algorithms. The American Academy of Neurology considered VEMP as an investigational technique (Fife et al, 2000). Guidelines prepared for the State of Colorado (DLE, 2006) state that VEMP "is currently a research tool and is not recommended for routine clinical use." In a review of the literature, Rauch (2006) states that VEMP holds great promise for diagnosing and monitoring Ménière's disease and some other neurotologic disorders. Rauch notes, however, that the methods, equipment, and applications for vestibular evoked myogenic potential testing are not yet standardized, and many aspects of vestibular evoked myogenic potential and its use have not yet been adequately studied or described.

Brantberg et al (2007) studied VEMP in response to sound stimulation (500 Hz tone burst, 129 dB SPL) in 1,000 consecutive patients. Vestibular evoked myogenic potentials from the ear with the larger amplitude were evaluated based on the assumption that the majority of the tested patients probably had normal vestibular function in that ear. Patients with known bilateral conductive hearing loss, with known bilateral vestibular disease and those with Tullio phenomenon were not included in the evaluation. It was found that there was an age-related decrease in VEMP amplitude and an increase in VEMP latency that appeared to be rather constant throughout the whole age span. Vestibular evoked myogenic potentials data were also compared to an additional group of 10 patients with Tullio phenomenon. Although these 10 patients did have rather large VEMP, equally large VEMP amplitudes were observed in a proportion of unaffected subjects of a similar age group. Thus, the findings of a large VEMP amplitude in response to a high-intensity sound stimulation is not, per se, distinctive for a significant vestibular hypersensitivity to sounds.

Muyts et al (2007) provided an overview of vestibular function testing and highlights the new techniques that have emerged during the past 5 years. Since the introduction of video-oculography as an alternative to electro-oculography for the assessment of vestibular-induced eye movements, the investigation of the utricle has become a part of vestibular function testing, using unilateral centrifugation. Vestibular evoked myogenic potentials have become an important test for assessing saccular function, although further standardization and methodological issues remain to be clarified. Galvanic stimulation of the labyrinth also is an evolving test that may become useful diagnostically. The authors concluded that a basic vestibular function testing battery that includes ocular motor tests, caloric testing, positional testing, and earth-vertical axis rotational testing focuses on the horizontal semicircular canal. Newer methods to investigate the otolith organs are being developed. These new tests, when combined with standard testing, will provide a more comprehensive assessment of the complex vestibular organ.

In a systematic review, van Laerhoven et al (2013) examined the prognostic value of currently used clinical tests in neonatal patients with perinatal asphyxia and hypoxic-ischemic encephalopathy (HIE). Searches were made on MedLine, Embase, Central, and CINAHL for studies occurring between January 1980 and November 2011. Studies were included if they

evaluated outcome in term infants with perinatal asphyxia and HIE,
evaluated prognostic tests, and
reported outcome at a minimal follow-up age of 18 months.

Study selection, assessment of methodological quality, and data extraction were performed by 3 independent reviewers. Pooled sensitivities and specificities of investigated tests were calculated when possible. Of the 259 relevant studies, 29 were included describing 13 prognostic tests conducted 1,631 times in 1,306 term neonates. A considerable heterogeneity was noted in test performance, cut-off values, and outcome measures. The most promising tests were amplitude-integrated electroencephalography (sensitivity 0.93, [95 % CI: 0.78 to 0.98]; specificity 0.90 [0.60 to 0.98]), EEG (sensitivity 0.92 [0.66 to 0.99]; specificity 0.83 [0.64 to 0.93]), and VEPs (sensitivity 0.90 [0.74 to 0.97]; specificity 0.92 [0.68 to 0.98]). In imaging, diffusion weighted MRI performed best on specificity (0.89 [0.62 to 0.98]) and T1/T2-weighted MRI performed best on sensitivity (0.98 [0.80 to 1.00]). Magnetic resonance spectroscopy demonstrated a sensitivity of 0.75 (0.26 to 0.96) with poor specificity (0.58 [0.23 to 0.87]). The authors concluded that this evidence suggested an important role for amplitude-integrated electroencephalography, EEG, VEPs, and diffusion weighted and conventional MRI. Moreover, they stated that given the heterogeneity in the tests' performance and outcomes studied, well-designed, large prospective studies are needed.

Balzer et al (1998) reported on the results of a descriptive case series of the use of somatosensory evoked potentials during lumbrosacral spine surgery. SSEPs and EMG activity were simultaneously recorded for 44 patients who underwent surgical procedures to decompress and stabilize the lumbosacral spine, using pedicle screw instrumentation. Indications included degenerative spondylolisthesis (22), pars fracture with spondylolisthesis (9), failed back syndrome (7), burst/compression fracture (4), and instability from metastasis (2). The specific level of the lumbar spine for each procedure included in this series was not reported. All neurosurgical procedures were performed by a single surgeon. The authors reported that, in two cases, changes in SSEPs and spontaneous EMG activity were noted and were correlated with postoperative patient complaints.

Rothstein (2009) stated that the early recognition of comatose patients with a hopeless prognosis – regardless of how aggressively they are managed – is of utmost importance. Median SSEP supplement and enhance neurological examination findings in anoxic-ischemic coma and are useful as an early guide in predicting outcome. The key finding is that bilateral absence of cortical evoked potentials reliably predicts unfavorable outcome in comatose patients after cardiac arrest. The author studied 50 comatose patients with preserved brainstem function after cardiac arrest. All 23 patients with bilateral absence of cortical evoked potentials died without awakening. Neuropathological study in 7 patients disclosed widespread ischemic changes or frank cortical laminar necrosis. The remaining 27 patients with normal or delayed central conduction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurological deficit or death. Greater use of SSEP in anoxic-ischemic coma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.

An UpToDate review on "Hypoxic-ischemic brain injury: Evaluation and prognosis" (Weinhouse and Young, 2012) states that several ancillary tests have been studied in the period after anoxic injury; these are often helpful at arriving at an earlier prognostic determination than would be possible with clinical testing alone. Somatosensory evoked potentials are the averaged electrical responses in the central nervous system to somatosensory stimulation. Bilateral absence of the N20 component of the SSEP with median nerve stimulation at the wrist in the 1st week (usually between 24 and 72 hours) from the arrest has a pooled likelihood ratio of 12.0 (95 % confidence interval [CI]: 5.3 to 26.6) and a false-positive rate of zero % for an outcome no better than persistent vegetative state. Repeated testing should be considered when the N20 responses are present in the first 2 to 3 days from the cardiac arrest, as they may later disappear. The clinical operating characteristics of other evoked potentials (brainstem, auditory, visual, middle latency, and event-related) have not been adequately evaluated. Somatosensory evoked potentials are the best validated and most reliable of the ancillary tests currently available for clinical use.

The Quality Standards Subcommittee of the American Academy of Neurology's Practice Parameter on "Prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review)" (Wijdicks et al, 2006) recommended the assessment of poor prognosis can be guided by the bilateral absence of cortical SSEPs (N20 response) within 1 to 3 days (recommendation level B).

Raggi et al (2010) noted that amyotrophic lateral sclerosis (ALS) is increasingly recognized to be a multi-system disease, involving associative areas in addition to the motor cortex and therefore affecting cognition. Patients with ALS may present with subtle behavioral and executive dysfunctions or, less frequently, with a manifest fronto-temporal dementia. Event-related potentials (ERPs) are a high-temporal resolution technique, which can be used to explore the presence of cognitive dysfunction. All the primary studies reviewed here have shown ERP abnormalities in groups of non-demented patients affected by sporadic ALS compared to healthy controls. The ERP results support findings of neuropsychological and imaging studies. The authors concluded that prospective studies combining simultaneous neuropsychological and imaging investigations are needed to assess the possible role of ERPs in the early detection and follow-up of cognitive dysfunction in ALS patients.

The U.S. Preventive Services Task Force (USPSTF) has not recommended vision screening of infants and young children. The 2011 USPSTF recommendation does not support vision screening for children less than 3 years of age, as it concludes that the current evidence is insufficient to assess the balance of benefits and harms to this subpopulation. This position is consistent with the current recommendations of the American Academy of Ophthalmology and the American Association for Pediatric Ophthalmology and Strabismus and other professional organizations.

In a review on "Facial nerve monitoring during cerebellopontine angle and skull base tumor surgery", Acioly et al (2013) stated that intraoperative neuromonitoring has been established as one of the methods by which modern neurosurgery can improve surgical results while reducing morbidity. Despite routine use of intraoperative facial nerve (FN) monitoring, FN injury still is a complication of major concern due to severe negative impact on patient's quality of life. Through searches of PubMed, these investigators provided a systematic review of the current literature up to February, 2011, emphasizing all respects of FN monitoring for cerebellopontine angle and skull base tumor surgery from description to current success on function prediction of standard and emerging monitoring techniques. Currently, standard monitoring techniques comprise direct electrical stimulation (DES), free-running electromyography (EMG), and facial motor evoked potential (FMEP). These researchers included 62 studies on function prediction by investigating DES (43 studies), free-running EMG (13 studies), and FMEP (6 studies) criteria. DES mostly evaluated post-operative function by using absolute amplitude, stimulation threshold, and proximal-to-distal amplitude ratio, whereas free-running EMG used the train-time criterion. The prognostic significance of FMEP was assessed with the final-to-baseline amplitude ratio, as well as the event-to-baseline amplitude ratio and waveform complexity. The authors concluded that although there is a general agreement on the satisfactory functional prediction of different electrophysiological criteria, the lack of standardization in electrode montage and stimulation parameters precludes a definite conclusion regarding the best method. Moreover, studies emphasizing comparison between criteria or even multi-modal monitoring and its impact on FN anatomical and functional preservation are still lacking in the literature.

Mauguiere et al (1997) examined if abnormalities of central conduction could be detected prospectively in patients with epilepsy treated with vigabatrin (VGB) as long-term add-on medication. A total of 201 patients with refractory partial epilepsy were enrolled and monitored for as long as 2 years. Vigabatrin was added to the treatment at an average dose of 2 to 3g/day. Conduction in somatosensory and visual pathways was assessed by median nerve SEP and pattern VEP recordings performed at inclusion and once every 6 months. The upper limit and test-retest variability of EP latencies were evaluated at time of enrollment in the patient group. Prolonged N13-N20 or P14-N20 SEP intervals and P100 VEP latency greater than 2.5 SD above the baseline mean, observed on repeated runs in the same session and exceeding the test-retest variability at enrollment were considered to indicate central conduction slowing. A total of 109 patients completed the 2-year study period, and 92 discontinued VGB, of whom 37 were monitored with regard to EP until the end of the study. No consistent change in SEP or VEP was observed in the entire group during VGB treatment. The number of occasional EP values outside the baseline range in patients treated with VGB similar to that in patients whose VGB treatment had been discontinued. The authors concluded that they detected no evidence of changes in SEP and VEP attributable to altered neuronal conduction in the CNS during long-term VGB treatment.

Zgorzalewicz and Galas-Zgorzalewicz (2000) estimated the effects of VGB as add-on therapy on VEP and BAEP. The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these anti-epileptic drugs (AEDs). Combination therapy was administered using add-on VGB in the recommended dose 57.4 +/- 26.5 mg/kg body weight/day. VEP and BAEP were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age-matched control group. Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the inter-peak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes. The authors concluded that adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs.

In a prospective cohort study, Zuniga et al (2012) characterized both cervical and ocular vestibular-evoked myogenic potential (cVEMP, oVEMP) responses to air-conducted sound (ACS) and midline taps in Meniere disease (MD), vestibular migraine (VM), and controls, and determined if cVEMP or oVEMP responses can differentiate MD from VM. Unilateral definite MD patients (n = 20), VM patients (n = 21) by modified Neuhauser criteria, and age-matched controls (n = 28) were included in this study; cVEMP testing used ACS (clicks), and oVEMP testing used ACS (clicks and 500-Hz tone bursts) and midline tap stimuli (reflex hammer and Mini-Shaker). Outcome parameters were cVEMP peak-to-peak amplitudes and oVEMP n10 amplitudes. Relative to controls, MD and VM groups both showed reduced click-evoked cVEMP (p < 0.001) and oVEMP (p < 0.001) amplitudes. Only the MD group showed reduction in tone-evoked amplitudes for oVEMP. Tone-evoked oVEMPs differentiated MD from controls (p = 0.001) and from VM (p = 0.007). The oVEMPs in response to the reflex hammer and Mini-Shaker midline taps showed no differences between groups (p > 0.210). The authors concluded that using these techniques, VM and MD behaved similarly on most of the VEMP test battery. A link in their pathophysiology may be responsible for these responses. The data suggested a difference in 500-Hz tone burst-evoked oVEMP responses between MD and MV as a group. However, no VEMP test that was investigated in segregated individuals with MD from those with VM.

Heravian et al (2011) assessed the usefulness of color vision, photo stress recovery time (PSRT), and VEP in early detection of ocular toxicity of hydroxychloroquine (HCQ), in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). A total of 86 patients were included in the study and divided into 3 groups: with history of HCQ use: interventional 1 (Int.1) without fundoscopic changes and Int.2 with fundoscopic changes; and without history of HCQ use, as control. Visual field, color vision, PSRT and VEP results were recorded for all patients and the effect of age, disease duration, treatment duration and cumulative dose of HCQ on each test was assessed in each group. There was a significant relationship among PSRT and age, treatment duration, cumulative dose of HCQ and disease duration (p < 0.001 for all). Color vision was normal in all the cases. P100 amplitude was not different between the 3 groups (p = 0.846), but P100 latency was significantly different (p = 0.025) and for Int.2 it was greater than the others. The percentage of abnormal visual fields for Int.2 was more than Int.1 and control groups (p = 0.002 and p = 0.005, respectively), but Int.1 and control groups were not significantly different (p > 0.50). In the early stages of maculopathy, P100 latencies of VEP and PSRT are useful predictors of HCQ ocular toxicity. In patients without ocular symptoms and fundoscopic changes, the P100 latency of VEP predicts more precisely than the others.

Current guidelines from the American Academy of Ophthalmology do not recommend visual evoked potentials for screening or diagnosis of hydroxychloroquine toxicity (Marmor, et al., 2011; Karmel, 2011; Scechtman and Karpecki, 2011). Shechtman and Karpecki (2011) noted that the 2011 testing guidelines for patients on Plaquenil listed

dilated fundus examination,
automated 10-2 VF,
spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF) or multi-focal electroretinography (mfERG) (if available), and
photography as screening tests.

Visual evoked potentials were not mentioned as a screening tool. Furthermore, the screening guidelines on “Hydroxychloroquine toxicity” by Schwartz and Mieler (2011) did not mention the use of VEP. An UpToDate Drug Information on “Hydroxychloroquine” notes that “Ophthalmologic exam at baseline and every 3 months during prolonged therapy (including visual acuity, slit-lamp, fundoscopic, and visual field exam); muscle strength (especially proximal, as a symptom of neuromyopathy) during long-term therapy”. Visual evoked potentials were not mentioned as a screening tool. Also, an UpToDate review on “Antimalarial drugs in the treatment of rheumatic disease” (Wallace, 2013) does not mention the use of VEPs.

evaluated outcome in term infants with perinatal asphyxia and HIE,
evaluated prognostic tests, and
reported outcome at a minimal follow-up age of 18 months.

In a retrospective analysis of a case series, Silverstein et al (2014) described a novel technique to monitor femoral nerve function by analyzing the saphenous nerve SSEP during transpsoas surgical exposures of the lumbar spine. Institutional review board approval was granted for this study and the medical records along with the intraoperative monitoring reports from 41 consecutive transpsoas lateral interbody fusion procedures were analyzed. The presence or absence of intraoperative changes to the saphenous nerve SSEP was noted and the post-operative symptoms and physical examination findings were noted. Changes in SSEP were noted in 5 of the 41 surgical procedures, with 3 of the patients waking up with a femoral nerve deficit. None of the patients with stable SSEP's developed sensory or motor deficits post-operatively. No patient in this series demonstrated intraoperative EMG changes indicative of an intraoperative nerve injury. The authors concluded that saphenous nerve SSEP monitoring may be a beneficial tool to detect femoral nerve injury related to transpsoas direct lateral approaches to the lumbar spine. These preliminary findings need to be validated by well-designed studies.

Fix and colleagues (2015) noted that amnesic mild cognitive impairment (MCIa) is often characterized as an early stage of Alzheimer's dementia (AD). The latency of the P2, an electroencephalographic component of the flash VEP (FVEP), is significantly longer in those with AD or MCIa when compared with controls. In a pilot study, these investigators examined the diagnostic accuracy of several FVEP-P2 procedures in distinguishing people with MCIa and controls. The latency of the FVEP-P2 was measured in participants exposed to a single flash condition and 5 double-flash conditions. The double-flash conditions had different inter-stimulus intervals between the pair of strobe flashes. Significant group differences were observed in the single-flash and 2 of the double-flash conditions. One of the double-flash conditions (100 ms) displayed a higher predictive accuracy than the single-flash condition, suggesting that this novel procedure may have more diagnostic potential. Participants with MCIa displayed similar P2 latencies across conditions, while controls exhibited a consistent pattern of P2 latency differences. These differences demonstrated that the double stimulation procedure resulted in a measurable refractory effect for controls but not for those with MCIa. The authors concluded that the pattern of P2 group differences suggested that those with MCIa have compromised cholinergic functioning that resulted in impaired visual processing. They stated that results from the present investigation lend support to the theory that holds MCIa as an intermediate stage between normal healthy aging and the neuropathology present in AD; and measuring the FVEP-P2 during several double stimulation conditions could provide diagnostically useful information about the health of the cholinergic system.

Loudness-Dependence of Auditory Evoked Potentials

In a pilot study, Uhl and colleagues (2012) measured serotonergic activity in a follow-up study of suicidal patients. In particular, these researchers examined if suicide attempts or suicidal states cause changes in the loudness dependence of auditory evoked potentials (LDAEP). A total of 13 patients (6 males; mean age of 40.9 ± 11.3 years; range of 20 to 61) with a major depressive episode who had attempted suicide or had suicidal plans (Hamilton Depression Rating Scale item 3 [suicidality] greater than or equal to 3) were included in the study; LDAEP and psychometric measurements took place about 2, 5, 9 and 16 days after attempted suicide or suicidal action. On day 9, LDAEP was significantly higher compared to day 2 and day 16; there was a similar tendency compared to day 5. Instability of central serotonergic function was suggested resulting in reduced serotonergic activity about 1 week after suicide attempt. The authors concluded that further studies are needed that include larger samples in order to distinguish between different psychiatric diseases and to consider confounding factors like gender, medication, smoking, impulsivity or lethality of suicidal action.

GraBnickel et al (2015) stated that differences in central serotonergic function due to affective disorders and due to extraordinary situations like suicidality may be visualized using the LDAEP. A total of 20 patients (11 males; mean age of 43.25 ± 10.85, age range of 20 to 61) suffering from a major depressive episode who had either acutely attempted suicide or who had suicidal plans and behavior, which were reflected by item 3 of Hamilton Depression Rating Scale greater than or equal to 3 (suicidality), were included in the study. Furthermore, these researchers compared subjects’ LDAEP to those of non-suicidal depressed patients as well as to healthy volunteers, each matched according to age and gender; LDAEP measurement and psychometric tests took place about 2, 5, 9, 16 and 30 days after acute suicidal action or suicide attempts. In contrast to previous results, significant differences in LDAEP could not have been shown in between the suicidal group, or by comparing results of suicidal patients to non-suicidal depressed patients or to healthy volunteers. However, when the LDAEP of non-suicidal depressed patients were compared to healthy volunteers, there was a trend for a higher LDAEP in the healthy volunteers. The authors concluded that further studies are needed to ascertain further influences on serotonergic function and confounding factors like medication, smoking, age, gender, co-morbidities and methods of suicidal attempt.

Pak et al (2015) noted that the relationship between suicidality and the LDAEP remains controversial. These investigators reviewed the literature related to the LDAEP and suicide in patients with major depressive disorder, and suggested future research directions. Serotonergic dysfunction in suicidality seems to be more complicated than was originally thought. Studies of suicide based on the LDAEP have produced controversial results, but it is possible that these were due to differences in study designs and the smallness of samples. For example, some studies have evaluated suicide ideation and the LDAEP, while others have evaluated suicide attempts and the LDAEP. Furthermore, some of the latter studies enrolled acute suicide attempters, while others enrolled those with the history of previous suicide attempts, irrespective of whether these were acute or chronic. Thus, a more robust study design is needed in future studies (e.g., by evaluating the LDAEP immediately after a suicide attempt rather than in those with a history of suicide attempts and suicide ideation in order to reduce bias). Moreover, the authors stated that genuine suicide attempt, self-injurious behaviors, and faked suicide attempt need to be discriminated in the future.

Motor Evoked Potentials for Evaluation of Wilson's Disease

Bembenek et al (2015) stated that Wilson's disease (WD) is a metabolic brain disease resulting from improper copper metabolism. Although pyramidal symptoms are rarely observed, sub-clinical injury is highly possible as copper accumulates in all brain structures. The usefulness of MEPs in pyramidal tracts damage evaluation still appears to be somehow equivocal. These investigators searched for original papers examining the value of transcranial magnetic stimulation (TMS) elicited MEPs with respect to motor function of upper and lower extremity in WD. They searched PubMed for original papers evaluating use of MEPs in WD using key words: "motor evoked potentials Wilson's disease" and "transcranial magnetic stimulation Wilson's disease". These researchers found 6 articles using the above key words. One additional article and 1 case report were found while viewing the references lists; thus, these investigators included 8 studies. Number of patients in studies was low and their clinical characteristic was variable; there were also differences in methodology. Abnormal MEPs were confirmed in 20 to 70 % of study participants; MEPs were not recorded in 7.6 to 66.7 % of patients. Four studies reported significantly increased cortical excitability (up to 70 % of patients). Prolonged central motor conduction time was observed in 4 studies (30 to 100 % of patients); 1 study reported absent or prolonged central motor latency in 66.7 % of patients. The authors concluded that although MEPs may be abnormal in WD, this has not been thoroughly assessed. Moreover, they stated that further studies are needed to evaluate MEPs' usefulness in evaluating pyramidal tract damage in WD.

Somatosensory Evoked Potentials as Prognostic Tests in Neonates with Hypoxic-Ischemic Encephalopathy

Garfinkle and colleagues (2015) noted that SEPs were reported to have high positive-predictive value (PPV) for neuro-developmental impairment (NDI) in neonates with moderate or severe hypoxic-ischemic encephalopathy (HIE). These researchers evaluated if this predictive value remains high with the use of therapeutic hypothermia. A cohort of HIE neonates treated with hypothermia was recruited between September 2008 and September 2010; SEPs were elicited after hypothermia and classified as bilateral absent N19, abnormal N19 (i.e., delayed or unilateral absent), or normal. Qualitative evaluation of MRI was also performed. The primary outcome was moderate or severe NDI around 2 years of age. Somatosensory evoked potentials were performed after hypothermia in 26 of 34 neonates submitted to hypothermia with adequate follow-up at a median day of life 11 (inter-quartile range [IQR]: 9 to 13). Twenty-three (88 %) had moderate encephalopathy; 11 neonates (42 %) had bilateral absent N19, 4 of whom had NDI, while 15 neonates (58 %) had either abnormal or normal N19, of whom only 1 had NDI. Somatosensory evoked potentials thus had a PPV of 0.36 (4/11) and a negative-predictive value (NPV) of 0.93 (14/15). Eighteen neonates (69 %) had brain injury on MRI; thus, MRI had a PPV of 0.28 (5/18) and an NPV of 1.00 (8/8). The authors concluded that neonates with HIE treated with hypothermia with bilateral absent N19 potentials may have a better prognosis than reported in the pre-hypothermia era; MRI also had a low PPV and high NPV. They stated that SEPs should be interpreted with caution in this new population and need to be re-evaluated in larger studies.

Visual Evoked Potentials for Evaluation of Birdshot Chorioretinopathy

Tzekov and Madow (2015) noted that birdshot chorioretinopathy (BSCR) is a rare form of autoimmune posterior uveitis that can affect the visual function and, if left untreated, can lead to sight-threatening complications and loss of central vision. These investigators performed a systematic search of the literature focused on visual electrophysiology studies, including ERG, electrooculography (EOG), and VEP, used to monitor the progression of BSCR and estimate treatment effectiveness. Many reports were identified, including using a variety of methodologies and patient populations, which made a direct comparison of the results difficult, especially with some of the earlier studies using non-standardized methodology. Several different electrophysiological parameters, such as EOG Arden's ratio and the mfERG response densities, are reported to be widely affected. However, informal consensus emerged in the past decade that the full-field ERG light-adapted 30-Hz flicker peak time is one of the most sensitive electrophysiological parameters. As such, it has been used widely in clinical trials to evaluate drug safety and effectiveness and to guide therapeutic decisions in clinical practice. The authors concluded that despite its wide use, a well-designed longitudinal multi-center study to systematically evaluate and compare different electrophysiological methods or parameters in BSCR is still lacking; but would benefit both diagnostic and therapeutic decisions.

Motor Evoked Potentials for Evaluation of Wilson's Disease

Bembenek and colleagues (2015) noted that Wilson's disease (WD) is a metabolic brain disease resulting from improper copper metabolism. Although pyramidal symptoms are rarely observed, sub-clinical injury is highly possible as copper accumulates in all brain structures. The usefulness of MEPs in pyramidal tracts damage evaluation still appears to be somehow equivocal. These investigators searched for original papers assessing the value of transcranial magnetic stimulation elicited MEPs with respect to motor function of upper and lower extremity in WD. They searched PubMed for original papers evaluating the use of MEPs in WD using key words: "motor evoked potentials Wilson's disease" and "transcranial magnetic stimulation Wilson's disease”. These investigators found 6 articles using the above key words; 1 additional article and 1 case report were found while viewing the references lists. Thus, a total of 8 studies were included in this analysis; number of participants in studies was low and their clinical characteristic was variable. There were also differences in methodology. Abnormal MEPs were confirmed in 20 to 70 % of study participants; MEPs were not recorded in 7.6 to 66.7 % of patients; 4 studies reported significantly increased cortical excitability (up to 70 % of patients). Prolonged central motor conduction time was observed in 4 studies (30 to 100 % of patients). One study reported absent or prolonged central motor latency in 66.7 % of patients. The authors concluded that although MEPs may be abnormal in WD, this has not been thoroughly assessed. They stated that further studies are needed to evaluate MEPs' usefulness in assessing pyramidal tract damage in WD.

Ocular Vestibular Evoked Myogenic Potentials for the Diagnosis of Myasthenia Gravis

In a case-control, proof-of-principle study, Valko and colleagues (2016) examined if ocular vestibular evoked myogenic potentials (oVEMP) can be used to detect a decrement in the extra-ocular muscle activity of patients with myasthenia gravis (MG). A total of 27 patients with MG, including 13 with isolated ocular and 14 with generalized MG, and 28 healthy controls were included in this study. These investigators applied repetitive vibration stimuli to the forehead and recorded the activity of the inferior oblique muscle with 2 surface electrodes placed beneath the eyes. To identify the oVEMP parameters with the highest sensitivity and specificity, these researchers evaluated the decrement over 10 stimulus repetitions at 3 different repetition rates (3 Hz, 10 Hz, and 20 Hz). Repetitive stimulation at 20 Hz yielded the best differentiation between patients with MG and controls with a sensitivity of 89 % and a specificity of 64 % when using a unilateral decrement of greater than or equal to 15.2 % as cut-off. When using a bilateral decrement of greater than or equal to 20.4 % instead, oVEMP allowed differentiation of MG from healthy controls with 100 % specificity, but slightly reduced sensitivity of 63 %. For both cut-offs, sensitivity was similar in isolated ocular and generalized MG. The authors concluded that the findings of this study demonstrated that the presence of an oVEMP decrement is a sensitive and specific marker for MG. This test allowed direct and non-invasive examination of extra-ocular muscle activity, with similarly good diagnostic accuracy in ocular and generalized MG. They stated that oVEMP represents a promising diagnostic tool for MG. This study provided Class III evidence that oVEMP testing accurately identifies patients with MG with ocular symptoms (sensitivity 89 %, specificity 64 %). Well-designed studies are needed to confirm the diagnostic utility of oVEMP in clinical practice.

In an editorial that accompanied the afore-mentioned study, Prasad and Halmagyi (2016) stated that cohort studies are needed to evaluate the value of oVEMP in clinical practice, where a broader range of diagnostic possibilities leaves the clinician uncertain.

Vestibular Evoked Myogenic Potentials for the Diagnosis of Meniere's Disease or Delayed Endolymphatic Hydrops

Akkuzu et al (2006) examined the role of VEMP in benign paroxysmal positional vertigo (BPPV) and Meniere's disease, and ascertained if this type of testing is valuable for assessing the vestibular system. The 62 participants included 17 healthy controls and 45 other subjects selected from patients who presented with the complaint of vertigo (25 diagnosed with BPPV and 20 diagnosed with Meniere's disease). Vestibular evoked myogenic potentials were recorded in all subjects and findings in each patient group were compared with control findings. Vestibular evoked myogenic potentials for the 30 affected ears in the 25 BPPV patients revealed prolonged latencies in 8 ears and decreased amplitude in 1 ear (9 abnormal ears; 30 % of total). The recordings for the 20 affected ears in the Meniere's disease patients revealed 4 ears with no response, 6 ears with prolonged latencies (10 abnormal ears; 50 % of total). Only 2 (5.9 %) of the 34 control ears had abnormal VEMP. The rate of VEMP abnormalities in the control ears was significantly lower than the corresponding rates in the affected BPPV ears and the affected Meniere's ears that were studied (p = 0.012 and p < 0.001, respectively). The results suggested that testing of VEMP is a promising method for diagnosing and following patients with BPPV paroxysmal positional vertigo and Meniere's disease.

Egami and associates (2013) estimated the sensitivity and specificity of VEMPs in comparison with caloric test in diagnosing MD among patients with dizziness. Data were retrospectively collected from 1,170 consecutive patients who underwent vestibular tests. Among them, 114 patients were diagnosed as having unilateral definite MD; VEMPs in response to clicks and short tone burst stimulation as well as caloric tests were performed. The sensitivity and specificity of each test were evaluated. The results of each test were compared with hearing level and staging of MD. The sensitivity and specificity of VEMPs were 50.0 % and 48.9 %, while those of the caloric test were 37.7 % and 51.2 %, respectively. There was no significant difference in hearing level between patients appropriately or inappropriately identified by VEMPs, whereas there was a significant difference in those of the caloric test. Combined use of VEMP and caloric test increased the sensitivity to 65.8 %. The authors concluded that although the sensitivity and specificity of VEMPs in diagnosing MD were not high, they were comparable to those of caloric test. They stated that VEMPs as well as caloric testing may give additional information as part of a diagnostic test battery for detecting vestibular abnormalities in MD.

In a systematic review and meta-analysis, Zhang and colleagues (2015) evaluated the clinical diagnostic value of VEMPs for endolymphatic hydrops (EH). The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio (OR) and area under summary receiver operating characteristic curves (AUC) were calculated. Subgroup analysis and publication bias assessment were also conducted. The pooled sensitivity and the specificity were 49 % (95 % CI: 46 % to 51 %) and 95 % (95 % CI: 94 % to 96 %), respectively. The pooled positive likelihood ratio was 18.01 (95 % CI: 9.45 to 34.29) and the pooled negative likelihood ratio was 0.54 (95 % CI: 0.47 to 0.61); AUC was 0.78 and the pooled diagnostic OR of VEMPs was 39.89 (95 % CI: 20.13 to 79.03). The authors concluded that the findings of the present meta-analysis showed that VEMPs test alone is not sufficient for the diagnosis of MD or delayed EH, but that it might be an important component of a test battery for diagnosing MD or delayed EH. Moreover, VEMPs, due to its high specificity and non-invasive nature, might be used as a screening tool for EH.

Furthermore, an UpToDate review on “Meniere disease” (Moskowitz and Dinces, 2016) states that “Meniere disease is a clinical diagnosis. Although not diagnostic, patients should undergo audiometry, vestibular testing, and MRI to rule out other causes of symptoms. The vestibular evoked myogenic potential (VEMP) test may be useful for monitoring disease progression”.

Cervical and Ocular Vestibular Evoked Myogenic Potential Testing

On behalf of the American Academy of Neurology (AAN), Fife and colleagues (2017) reviewed the evidence and made recommendations regarding the diagnostic utility of cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP, respectively). Four questions were asked:

does cVEMP accurately identify superior canal dehiscence syndrome (SCDS)?
does oVEMP accurately identify SCDS?
for suspected vestibular symptoms, does cVEMP/oVEMP accurately identify vestibular dysfunction related to the saccule/utricle? and
for vestibular symptoms, does cVEMP/oVEMP accurately and substantively aid diagnosis of any specific vestibular disorder besides SCDS?

The guideline panel identified and classified relevant published studies (January 1980 to December 2016) according to the 2004 AAN process. The following recommendations were provided:

Level C positive: Clinicians may use cVEMP stimulus threshold values to distinguish SCDS from controls (2 Class III studies) (sensitivity 86 % to 91 %, specificity 90 % to 96 %). Corrected cVEMP amplitude may be used to distinguish SCDS from controls (2 Class III studies) (sensitivity 100 %, specificity 93 %). Clinicians may use oVEMP amplitude to distinguish SCDS from normal controls (3 Class III studies) (sensitivity 77 % to 100 %, specificity 98 % to 100%). oVEMP threshold may be used to aid in distinguishing SCDS from controls (3 Class III studies) (sensitivity 70 % to 100 %, specificity 77 % to 100 %).
Level U: Evidence is insufficient to determine whether cVEMP and oVEMP can accurately identify vestibular function specifically related to the saccule/utricle, or whether cVEMP or oVEMP is useful in diagnosing vestibular neuritis or Meniere disease.
Level C negative: It has not been demonstrated that cVEMP substantively aids in diagnosing benign paroxysmal positional vertigo, or that cVEMP or oVEMP aids in diagnosing/managing vestibular migraine.

Visual Evoked Potential for Evaluation of Neuromyelitis Optica Spectrum Disorder

Ringelstein and colleagues (2020) examined if patients with neuromyelitis optica spectrum disorder (NMOSD) develop sub-clinical visual pathway impairment independent of acute attacks. A total of 548 longitudinally assessed full-field VEP of 167 patients with NMOSD from 16 centers were retrospectively evaluated for changes of P100 latencies and P100-N140 amplitudes. Rates of change in latencies (RCL) and amplitudes (RCA) over time were analyzed for each individual eye using linear regression and compared using generalized estimating equation models. The rates of change in the absence of optic neuritis (ON) for minimal VEP intervals of greater than or equal to 3 months between baseline and last follow-up were +1.951 ms/y (n = 101 eyes; SD = 6.274; p = 0.012) for the P100 latencies and -2.149 µV/y (n = 64 eyes; SD = 5.013; p = 0.005) for the P100-N140 amplitudes. For minimal VEP intervals of greater than or equal to 12 months, the RCL was +1.768 ms/y (n = 59 eyes; SD = 4.558; p = 0.024) and the RCA was -0.527 µV/y (n = 44 eyes; SD = 2.123; p = 0.111). The history of a previous ON of greater than 6 months before baseline VEP had no influence on RCL and RCA. ONs during the observational period led to mean RCL and RCA of +11.689 ms/y (n = 16 eyes; SD = 17.593; p = 0.003) and -1.238 µV/y (n = 11 eyes; SD = 3.708; p = 0.308), respectively. The authors concluded that this first longitudinal VEP study of patients with NMOSD provided evidence of progressive VEP latency delay occurring independently of acute ON. These researchers stated that prospective longitudinal studies are needed to corroborate these findings and help to interpret the clinical relevance.

Auditory Evoked Potential for Evaluation of Hearing and Language Deficits in Survivors of Extracorporeal Membrane Oxygenation

Lott et al (1990) examined clinical and neurophysiologic measures in 10 children aged 4 to 9 years after neonatal extracorporeal membrane oxygenation (ECMO). Electroencephalograms (EEG) did not correlate with clinical or other neurophysiologic measures of inter-hemispheric asymmetry. By ultrasound (US) imaging, the right internal carotid artery velocity was approximately 62 % of that on the left, and right internal carotid flow was reduced by 74 % (p ≤ 0.01), whereas an age-matched control group showed no differences. A decrease in the amplitude of the long-latency AEP and SSEP was noted over the right hemisphere after left-sided stimulation compared with the left hemispheric potentials after right-sided stimulation (p ≤ 0.005). No significant differences in hemispheric symmetry were noted in the amplitudes for wave V of the auditory brain-stem response (ABSR) or in the P30 component of the middle-latency AEPs. Likewise, latency measures of the evoked potentials were symmetric. The authors concluded that neonatal ECMO was associated with long-lasting decreased right internal carotid blood flow with compensatory increased flow through the left carotid system; and there was a consistent reduction in the amplitude of right hemispheric long-latency evoked potentials. These latter findings may reflect re-directed cerebral blood flow (CBF) patterns after ECMO.

Desai et al (1997) examined the sensitivity and specificity of neonatal BAEP as markers for subsequent hearing impairment and for developmental problems found later in infancy and childhood. BAEP studies were performed before discharge in infants treated with ECMO, and 2 specific abnormalities were analyzed: elevated threshold and delayed central auditory conduction. Behavioral audiometry was repeated during periodic follow-up until reliable responses were obtained for all frequencies, and standardized developmental testing was also conducted. The sensitivity and specificity of an elevated threshold on the neonatal BAEP for detecting subsequent hearing loss, and the relationship of any neonatal BAEP abnormality to language or developmental disorders in infancy, were calculated. Test results for 46 ECMO-treated infants (57.5 %) were normal, and those for 34 infants (42.5 %) were abnormal, with either elevated wave V threshold, prolonged wave I-V interval, or both on neonatal BAEP recordings. Most significantly, 7 (58 %) of the 12 children with subsequent sensorineural hearing loss (SNHL) had left the hospital after showing normal results on threshold tests. There was no significant difference in the frequency of hearing loss between subjects with abnormal (5/21, or 24 %) and those with normal BAEP thresholds (7/59, or 12 %; Fisher Exact Test, p = 0.28). Thus, the sensitivity of neonatal BAEP testing for predicting subsequent hearing loss was only 42 %. Neonatal BAEP specificity for excluding subsequent hearing loss was 76 %. In contrast, on language development testing, 19 children demonstrated receptive language delay. Of these children, 12 (63 %) had abnormal neonatal BAEP recordings and 7 (37 %) had a normal BAEP threshold, normal central auditory conduction test results, or both (p = 0.04). The authors concluded that neonatal BAEP threshold recordings were of limited value for predicting subsequent hearing loss common in ECMO-treated survivors. However, an abnormal neonatal BAEP significantly increased the probability of finding a receptive language delay during early childhood, even in those with subsequently normal audiometry findings. Because neonatal ECMO is associated with a high risk of hearing and receptive language disorders, parents should be counseled that audiologic and developmental follow-up evaluations in surviving children are essential regardless of the results of neonatal BAEP testing.

Weichbold et al (2006) determined the percentage of children who have a post-natal permanent childhood hearing impairment (PCHI) and the percentage thereof who have risk indicators for a post-natal hearing loss. Data were drawn retrospectively from the clinical charts of children who had bilateral PCHI (greater than 40 dB hearing level, better ear, un-aided) and had undergone universal newborn hearing screening (UNHS) between 1995 and 2000 in various Austrian hospitals. A hearing loss was recognized as post-natal when a child passed UNHS but was later found to have a hearing impairment. The presence of risk indicators, as suggested by the Year 2000 Statement of the American Joint Committee on Infant Hearing (JCIH), was assessed by reviewing the children's clinical charts. Of a total of 105 children with bilateral PCHI, 23 (22 %) showed post-natal impairment. After correction of this number for under-ascertainment, post-natal impairment was estimated to account for 25 % of all bilateral PCHI at age of 9 years. Risk indicators were found in 17 children but did not fully correspond to those proposed by the JCIH. The risk factors found were a family history of hearing loss (n = 3 children), meningitis (n = 2), cranio-facial malformation (n = 2), persistent pulmonary hypertension (n = 1), congenital cytomegaly infection (n = 1), ECMO (n = 1), recurrent otitis media with effusion (n = 1), and, in addition to the JCIH list, ototoxic therapy (n = 5), and birth before 33rd gestational week (n = 2) (1 child had a combination of the last 2); 6 children showed no risk indicators for the post-natal hearing loss. The authors concluded that these findings suggested that approximately 25 % of bilateral childhood hearing loss was post-natal, which supported the leading role of UNHS in detecting PCHI. Provisions for also identifying post-natal cases nevertheless were justified. Because in some of these children no risk indicators were detectable and in others the hearing deterioration started after age 3 years, audiologic monitoring of at-risk children up to this age may not be sufficient. Additional methods, such as hearing screening at nursery schools or schools, were recommended.

Ocular Vestibular Evoked Myogenic Potentials for Diagnosis of Myasthenia Gravis

De Meel et al (2020) validated the repetitive ocular vestibular evoked myogenic potentials (RoVEMP) test for diagnostic use in myasthenia gravis (MG) and examined its value in diagnostically challenging subgroups. The RoVEMP test was carried out in 92 patients with MG, 22 healthy controls, 33 patients with a neuromuscular disease other than MG (neuromuscular controls), 4 patients with Lambert-Eaton myasthenic syndrome, and 2 patients with congenital myasthenic syndrome. Mean decrement was significantly higher in patients with MG (28.4 % ± 32.2) than in healthy controls (3.2 % ± 13.9; p < 0.001) or neuromuscular controls (3.8 % ± 26.9; p < 0.001). With neuromuscular controls as reference, a cut-off of greater than or equal to 14.3 % resulted in a sensitivity of 67 % and a specificity of 82 %. The sensitivity of the RoVEMP test was 80 % in ocular MG and 63 % in generalized MG. The RoVEMP test was positive in 6 of 7 patients with sero-negative MG (SNMG) with isolated ocular weakness. Of 10 patients with SNMG with negative repetitive nerve stimulation (RNS) results, 73 % had an abnormal RoVEMP test . The magnitude of decrement was correlated with the time since the last intake of pyridostigmine (B = 5.40; p = 0.019). The authors concluded that the RoVEMP test is a new neurophysiologic test that, in contrast to RNS and single-fiber EMG, was able to measure neuromuscular transmission of extra-ocular muscles, which are the most affected muscles in MG. Especially in diagnostically challenging patients with negative antibody tests, negative RNS results, and isolated ocular muscle weakness, the RoVEMP test has a clear added value in supporting the diagnosis of MG. This study provided Class III evidence that RoVEMP distinguishes MG from other neuromuscular diseases.

The authors stated that drawbacks of this study included the single center of inclusion and this study population within a tertiary referral center that may not fully reflect the total MG population due to a referral bias. The control group of neuromuscular patients did not reflect the whole range of patients with diplopia due to a neuromuscular disease other than MG. However, these researchers included control patients with disorders that were previously reported to cause diagnostic confusion and delay due to similarities in presenting symptoms compared to OMG. Methodologic limitations of this trial included the fact that inter-rater reliability was not formally examined and the fact that researchers were not blinded to clinical status. These methodologic limitations were likely to have a minimal impact because the role of the investigator was limited to placing electrodes, encouraging the patient to relax, and placing the mini-shaker, but further studies on reliability will still be needed to prove this. All post-processing and decrement calculation were fully automated by a Matlab script. Another limitation was the (current) impossibility of including patients with excessive blinking in response to the vibrations. In this study, these investigators have excluded 3 % of the subjects due to this problem. By further optimizing stimulus parameters, altering the procedure of testing in patients with excessive blinking (e.g., lowering the stimulus intensity), and optimizing postprocessing, these researchers hope to increase diagnostic yield in future studies. The RoVEMP results of 1 patient with MG, 2 healthy controls, and 2 neuromuscular controls were not analyzable due to excessive blink artifacts and were excluded.

Short-Latency Somatosensory Evoked Potential (SSEP) Study for Evaluation of Movement Disorders

Pratt et al (1979) recorded short-latency SSEP by mechanical stimulation by surface electrodes over the digital nerves in the index finger, the median nerve at the wrist, the median nerve near the axilla, the brachial plexus, the cervical cord at CII, and the scalp overlying the somatosensory cortex. Nerve conduction velocities (NCVs) varied inversely with age and ranged from 43 to 68 m/sec. Mechanically evoked potentials recorded from the electrodes overlying the digital nerves were an artifact of the finger movement. All other electrode configurations recorded potentials comparable to those evoked by electrical stimulation of nerves. The authors concluded that these mechanically evoked potentials could prove useful in the evaluation of clinical disorders of somatosensory function from receptor to cortex in man.

UpToDate reviews on “Hyperkinetic movement disorders in children” (Jankovic, 2020), and “Functional movement disorders” (Miyasaki, 2020) do not mention short-latency SSEP as a management option.

Cervical Vestibular Evoked Myogenic Potential (cVEMP) for the Evaluation of Vertigo

Lee et al (2017) noted that vestibular-evoked myogenic potentials (VEMPs) can be abnormal in patients with idiopathic recurrent spontaneous vertigo. These researchers examined if abnormal cervical VEMPs (cVEMPs) can predict evolution of isolated recurrent vertigo into Meniere's disease (MD). They had followed-up 146 patients with isolated recurrent vertigo and an evaluation of cVEMPs for 0 to 142 months [median of 6, inter-quartile range (IQR) = 0 to 29] at the Dizziness Clinic of Seoul National University Bundang Hospital from June 2003 to May 2014. These investigators defined the variables associated with a progression into MD and calculated cumulative progression rates. Among the 94 patients with recurrent vertigo and abnormal cVEMPs, 18 (18/94, 19 %) showed an evolution into MD while only 2 of the 50 (4 %) patients with normal cVEMPs evolved into MD during the follow-up (p = 0.01). The interval between onset of vertigo and development of cochlear symptoms ranged from 1 month to 13.6 years (median of 3 years, IQR = 0.5 to 4.5 years). Overall, pure tone audiometry (PTA) threshold at 0.25-kHz [hazard ratio (HR) = 1.1, 95 % confidence interval (CI): 1.0 to 1.2] and abnormalities of cVEMPs (HR = 5.6, 95 % CI: 1.3 to 25.5) were found to be significantly associated with a later conversion into MD. The cumulative progression rate was 12 % (95 % CI: 5 to 18) at 1 year, 18 % (8 to 26) at 2 years, and 22 % (11 to 32) at 3 years. The authors concluded that abnormal cVEMPs may be an indicator for evolution of isolated recurrent vertigo into MD. Patients with isolated recurrent vertigo may be better managed conforming to MD when cVEMPs are abnormal.

Semmanaselvan et al (2019) stated that VEMP abnormalities in individuals with benign paroxysmal positional vertigo (BPPV) are often reported to be associated with utricle and saccule degeneration. These researchers evaluated the frequency of VEMP abnormalities using VEMPs in individuals with posterior canal BPPV after Epley's maneuver. A total of 36 individuals (36 ears) with definite posterior canal BPPV and 36 healthy controls were considered for the present study. All subjects underwent otoscopic examination, Dix-Hallpike maneuver to diagnose posterior canal BPPV. Further audiological evaluation including PTA was performed to rule out vestibular disorders associated with hearing loss. Epley's maneuver was performed on all individuals with BPPV by an experienced otorhinolaryngologist. Cervical and ocular VEMP were used to examine the saccule and utricle functions following Epley's maneuver . Cervical VEMP (cVEMP) and ocular VEMP (oVEMP) abnormalities were observed in 8/36 (22.22 %) and 18/36 (50 %) affected ears with BPPV, respectively. Cervical VEMP responses were reduced in amplitude among 1/36 (2.77 %) and absent in 7/36 (19.44 %) of affected ears with BPPV. Ocular VEMP responses were reduced in amplitude on 11/36 (30.55 %), followed by absent responses in 5/36 (13.88 %) ears with BPPV; 2 patients with posterior canal BPPV i.e., 4/64 (5.55 %) ears had bilateral absence of oVEMP responses. Two ears with BPPV 2/36 (5.55 %) had absence of both cVEMP and oVEMP responses in BPPV affected ear. T-test showed significant difference (p < 0.01) in the amplitude of oVEMP among posterior canal BPPV individuals when compared to cVEMP. The authors concluded that the findings of this study highlighted individuals with posterior canal BPPV may have otoconia dislodgement or macular degeneration of utricle, saccule, both utricle and saccule unilaterally, or bilaterally. These researchers stated that VEMP may be useful in evaluating degeneration of both otolith organs associated with BPPV.

Xu et al (2019) examined the diagnostic value of VEMP (cVEMP and oVEMP), caloric test, and cochlear electrogram (EcochG) in patients with Meniere's disease (MD) and non-MD. A total of 64 patients (64 ears) with unilateral MD were enrolled in the study group (MD group), and 127 cases (254 ears) of non-MD patients as non-MD group, including vertigo migraine in 40 cases, BPPV in 48 cases, benign recurrent vertigo in 13 cases, vestibular paroxysmia in 3 cases, vestibular neuritis in 5 cases and other undiagnosed vertigo in 18 cases. Both groups underwent cVEMP, oVEMP, caloric test and ECochG. Medcale software was used to draw ROC curve of ECochG and calculate the area under curve (AUC), Jordan index and optimal diagnostic cut-off points. The cut-off point was the point of -SP/AP, then the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of cVEMP, oVEMP, caloric test and ECochG in MD group and non-MD group were evaluated. The AUC of ECochG ROC curve was 0.74, the Jordan index was 0.47 and the cut-off point was 0.4. The sensitivity and specificity of cVEMP (62 % and 68 %), oVEMP (61 % and 53 %), and caloric test (53 % and 57 %) were all below ECochG (65 % and 78 %). The PPV of ECochG was the highest (61.9 %, the NPV of cVEMP was highest (87.5 %). The diagnostic accuracy of ECochG was highest (74 %), followed with cVEMP (67 %), oVEMP (55 %) and caloric test (56 %). The authors concluded that compared with the vestibular function tests, the sensitivity, specificity, diagnostic accuracy and NPV were all higher in ECochG, and the diagnostic benefit can be maximized when -SP/AP value greater than 0.4. Thus, the value of single vestibular function examination in the diagnosis of Meniere's disease is limited. The diagnosis of MD still requires a comprehensive evaluation in combination with medical history, audiological tests and vestibular function examinations.

Gunes et al (2020) noted that cVEMP measurements still do not have standard normative values in posterior canal BPPV. These researchers compared cVEMP recordings obtained with different stimuli applied in 2 different intensities in posterior canal BPPV patients. A total of 34 patients with unilateral posterior canal BPPV were included in the patient group. In cVEMP recordings obtained with different stimulus intensity [95 dB HL and 105 dB HL] and different stimuli [tone-burst cVEMP (T-cVEMP) and click cVEMP (C-cVEMP)]. When the C-cVEMP and T-cVEMP findings were compared in the patient group, differences were observed only in peak-to-peak p1-n1 amplitude values in the measurements performed with 95 dB stimulus; however, T-cVEMP measurements performed with 105-dB stimulus showed that both p1 and n1 latency values were longer and peak-to-peak p1-n1 amplitude values were higher than C-cVEMP measurements. The authors recommended using pure tone-burst stimulus for measurements with 105-dB HL in cVEMP evaluations they would perform in posterior BPPV patients. Both stimulants can be used when 95-dB HL stimuli is used.

Furthermore, an UpToDate review on “Evaluation of the patient with vertigo” (Furman and Barton, 2021) states that “cVEMPs are especially useful for detecting superior semicircular canal dehiscence syndrome, which will manifest as a cVEMP with a reduced threshold”.

Ocular Vestibular Evoked Myogenic Potential (oVEMP) for the Diagnosis of Benign Paroxysmal Positioning Vertigo

Xu et al (2016) stated that it is well-known that ocular vestibular evoked myogenic potentials (oVEMPs) predominantly reflect utricular function while cervical vestibular evoked myogenic potentials (cVEMPs) reflect saccular function. To-date, there are no published reports on the systemic evaluation of utricular and saccular function in benign paroxysmal positional vertigo (BPPV), nor are there any reports on the differences in VEMPs between patients with recurrent and non-recurrent BPPV. These researchers examined the difference in cervical and ocular (c/o)VEMPs between patients with BPPV and normal controls, as well as between patients with recurrent and non-recurrent BPPV. A total of 30 patients with posterior canal BPPV and 30 healthy subjects (as normal controls) were prospectively enrolled. cVEMP and oVEMP testing using 500 Hz tone-burst stimuli were performed on all. VEMP tests were repeated 3 times on each subject to ensure reliability and reproducibility of responses. VEMPs were defined as present or absent. Abnormal VEMP was defined by lack of VEMP response. In the control group, abnormal cVEMPs responses were detected in 6.67 % and abnormal oVEMPs responses were detected in 3.34 %. In BPPV patients (10 with recurrent BPPV, 20 with non-recurrent BPPV), abnormal cVEMPs responses were detected in 30 % and abnormal oVEMPs responses were detected in 56.7 %. More patients with BPPV showed abnormal responses in c/oVEMPs as compared to the control group (p < 0.05). oVEMPs was more often abnormal as compared to cVEMPs in BPPV patients (p < 0.05). There was no statistical difference between abnormal cVEMP responses in non-recurrent BPPV patients (25 %) and recurrent BPPV patients (40 %) (p > 0.05). Differences in abnormal oVEMP responses (non-recurrent BPPV, 40 %; recurrent BPPV, 90 %) were significant (p < 0.05). The authors concluded that an increased occurrence of abnormal c/oVEMP recordings appeared in BPPV patients, possibly as a result of degeneration of the otolith macula. oVEMPs were more often abnormal in BPPV patients as compared to cVEMPs, suggesting that utricular dysfunction may be more common than saccular dysfunction. Furthermore, oVEMP abnormalities in the recurrent BPPV group were significantly higher than those in the non-recurrent BPPV group. These researchers stated that assessment of c/oVEMPs in BPPV patients may therefore be of prognostic value in predicting likelihood of BPPV recurrence.

The authors stated that considering the controversy in the stability and repeatability of c/oVEMPs, they defined abnormal c/oVEMPs as absent responses in this study. As a result, these investigators did not analyze the latency and amplitude of the waves in c/oVEMPs. The main drawback of this study was the small number of BPPV patients (n = 30). As the incidence of BPPV is higher in the elderly and the average age of this study patients was under 60 years, there was a potential bias in the research. In future research, a larger sample size will be obtained such that quantitative analysis of otolith function in BPPV patients can be performed.

Semmanaselvan et al (2019) stated that VEMP abnormalities in individuals with BPPV are often reported to be associated with utricle and saccule degeneration. These investigators examined the frequency of VEMP abnormalities using VEMPs in individuals with posterior canal BPPV after Epley's maneuver. A total of 36 individuals (36 ears) with definite posterior canal BPPV and 36 healthy controls were considered for the present study. All of them underwent otoscopic examination, Dix-Hallpike maneuver to diagnose posterior canal BPPV. Further audiological evaluation including pure tone audiometry was performed to rule out vestibular disorders associated with hearing loss. Epley's maneuver was carried out on all individuals with BPPV by an experienced otorhinolaryngologist. cVEMP and oVEMP were used to examine the saccule and utricle functions following Epley's maneuver’ cVEMP and oVEMP abnormalities were observed in 8/36 (22.22 %) and 18/36 (50 %) affected ears with BPPV, respectively. Cervical VEMP responses were reduced in amplitude among 1/36 (2.77 %) and absent in 7/36 (19.44 %) of affected ears with BPPV; oVEMP responses were reduced in amplitude on 11/36 (30.55 %), followed by absent responses in 5/36 (13.88 %) ears with BPPV. Two patients with posterior canal BPPV i.e., 4/64 (5.55 %) ears had bilateral absence of oVEMP responses. Two ears with BPPV 2/36 (5.55 %) had absence of both cVEMP and oVEMP responses in BPPV affected ear. T-test showed significant difference (p < 0.01) in the amplitude of oVEMP among posterior canal BPPV individuals when compared to cVEMP. The authors concluded that this study highlighted individuals with posterior canal BPPV may have otoconia dislodgement or macular degeneration of utricle, saccule, both utricle and saccule unilaterally, or bilaterally. These researchers stated that VEMP may be useful in evaluating degeneration of both otolith organs associated with BPPV.

Oya et al (2019) noted that as the pathological cause of benign paroxysmal positional vertigo (BPPV), the dislocation or degeneration of otoconia in the utricle and saccule is suggested; and VEMP could reflect otolithic dysfunction due to these etiologies of BPPV. In a meta-analysis, these researchers examined the clinical significance of cVEMP and oVEMP in BPPV. Articles related to BPPV with data on cVEMP and oVEMP were collected. The following keywords were used to search PubMed and Scopus for English language articles: benign paroxysmal positional vertigo or BPPV and vestibular evoked myogenic potential or VEMP. The p13 latency in cVEMP and n1 latency in oVEMP were slightly but significantly prolonged in BPPV patients compared to control patients. AR in oVEMP of BPPV patients also showed higher value than that of control patients. However, the n23 latency and AR in cVEMP and p1 latency in oVEMP showed no significant difference between BPPV and control patients. Furthermore, latencies in VEMPs also showed no significant difference between an affected and a non-affected ear in BPPV patients. The authors concluded that the findings of this meta-analysis indicated that otolith dysfunction of BPPVs was detected by latencies in VEMPs, and AR in oVEMP more sensitively reflected the difference between affected and non-affected ears in BPPV patients. The otolith dysfunction of BPPV might be induced by the systemic condition. However, the differences of latencies between BPPV patients and control patients were too small to use VEMPs as a prognostic predictor.

Chen et al (2020) compared utricular dysfunction with saccular dysfunction in BPPV, based on oVEMP and (cVEMP, respectively. These researchers carried out a literature search examining utricular and saccular dysfunction in BPPV patients through June 2020 using oVEMP and cVEMP, respectively. The databases included PubMed, Embase, CENTRAL, CNKI, Wan Fang Data, and CBM. The literatures were limited to Chinese and English. Inclusion criteria and exclusion criteria were defined. These investigators adopted abnormal rate as the outcome. All statistical processes were performed by means of software Review Manager. Considering the air-conducted sound (ACS) and bone conducted vibration (BCV) may have different mechanisms, and 3 types of diagnostic criteria for abnormal VEMP were available, sub-group analysis was performed simultaneously according to the sound stimuli and the diagnostic criteria of abnormal VEMP. The authors retrieved 828 potentially relevant literatures, and finally 12 studies were included for meta-analysis of abnormal rate after duplication removal, titles and abstracts screening, and full-text reading. The abnormal rate of oVEMP was not significantly different from cVEMP (odds ratio [OR] = 1.59, 95 % confidence interval [CI]: 0.99 to 2.57). But the abnormal rate was obviously different between the subgroups adopting ACS oVEMP and BCV oVEMP. In studies adopting ACS oVEMP, the abnormal rate of oVEMP was higher than cVEMP (OR = 1.85, 95 % CI: 1.38 to 2.49). The abnormal rate of oVEMP was also higher than cVEMP when adopting asymmetry ratio (AR) and no response (NR) as diagnostic criteria (OR = 2.16, 95 % CI: 1.61 to 2.89). The authors concluded that this meta-analysis revealed that in oVEMP, the abnormal rate has been higher using ACS when compared to BCV, showing that BCV appeared to be more specific for the evaluation of utricular dysfunction. And in studies adopting ACS cVEMP and ACS oVEMP, the abnormal rate of oVEMP was higher than cVEMP. And the abnormal rate of oVEMP in BPPV patients was also higher than cVEMP with no heterogeneity if adopting AR and NR as diagnostic criteria. It was inferred that utricular dysfunction may be more predominant in BPPV compared with saccular dysfunction. These researchers stated that well-designed studies with large sample and normal control group and uniform parameters of VEMP testing are needed to further examine the otolith dysfunction of BPPV patients.

The authors stated that this review/meta-analysis had several drawbacks. First, a part of the studies adopted different stimulation modes, such as ACS and BCV. Even if they all adopted ACS, the intensity and frequency of acoustic stimuli may have a little difference. And only 1 study on BCV oVEMP was included in the meta-analysis. Second, the different diagnostic criteria for abnormal VEMP resulted in large heterogeneity. Third, the mean ages of BPPV individuals in the included articles were different from each other, and normal control group was absent.

Furthermore, an UpToDate review on “Benign paroxysmal positional vertigo” (Barton, 2021) does not mention vestibular evoked myogenic potential as a management option.

Olfactory Event‐Related Potential for the Evaluation of Long-Term COVID-19

Mazzatenta et al (2021) noted that COVID-19 is a public health emergency with cases increasing globally. Its clinical manifestations range from asymptomatic and acute respiratory disease to multi-organ dysfunction syndromes and effects of COVID-19 in the long-term. Interestingly, regardless of variant, all COVID-19 share impairment of the sense of smell and taste. These investigators reported, as far as they knew, the first comprehensive neurophysiological evaluation of the long-term effects of SARS-CoV-2 on the olfactory system with potential-related neurological damage. The case report concerned a military doctor, with a monitored health history, infected in April 2020 by the first wave of the epidemic expansion while on military duty in Codogno (Milan). In this subject, these researchers found the electrophysiological signal in the periphery, while its correlate was absent in the olfactory bulb region than in whole brain recordings. In agreement with this result was the lack of metabolic signs of brain activation under olfactory stimulation. Consequently, quantitative and qualitative diagnoses of anosmia were made by means of olfactometric tests. The authors strongly suggested a comprehensive series of olfactometric tests from the first sign of COVID-19 and subsequent patient assessments; and concluded that electrophysiological tests (olfactory event‐related potential and olfactory real‐time volatile organic compound test) and metabolic tests of olfactory function have made it possible to study the long-term effects and the establishment of neurological consequences.

Furthermore, an UpToDate review on “COVID-19: Evaluation and management of adults following acute viral illness” (Mikkelsen and Abramoff, 2021) states that “Olfactory/gustatory symptoms -- For patients who experienced a loss or decrease in their sense of smell or taste with acute COVID-19, we inquire about the degree of residual impairment and if their appetite or weight have been affected. Weight loss can be significant for some patients after critical illness for multifactorial reasons, and taste and smell impairment may contribute. In most cases, symptoms resolve slowly over several weeks and do not require intervention except for education regarding food and home safety. Patients with persistent gustatory and/or olfactory dysfunction may benefit from olfactory training, and self-guided programs are available online. If symptoms fail to resolve, further evaluation by an otolaryngologist may be needed, particularly in the setting of accompanying upper airway symptoms. Although not widely available, referral to a specialized taste and smell clinic may also be considered”. This review does not mention the sue of event‐related potentials as a management tool.

Pre-Operative SSEP of the Bilateral Tibial Somatosensory Pathways Prior To Scoliosis Surgery

In a prospective study, Shen et al (1996) reported the findings of 72 patients with the clinical diagnosis of adolescent idiopathic scoliosis (AIS) who underwent routine pre-operative magnetic resonance imaging (MRI) scans and neurologic consultations; 48 patients also had pre-operative somatosensory evoked potentials (SSEPs). All patients had normal neurologic examinations. Abnormal findings included 2 patients with Chiari type I malformation and 1 with a finding of a fatty collection in a vertebral body. In 4 cases, interpretation of the MRI was suspicious or equivocal, necessitating a computed tomography (CT) myelogram or other additional studies for clarification. Abnormal pre-operative SEP results were obtained in 3 patients, none of which proved significant. All surgical patients underwent instrumentation and fusion without incident. The authors concluded that the findings of this study indicated that routine preoperative SSEP is not necessary. Routine preoperative MRI is probably not indicated in AIS if the patient has a normal neurologic examination.

Hausmann et al (2003) reported the findings of a prospective study of spinal MRI, electrophysiological recordings, and neurological examinations of 100 patients admitted for surgery for AIS, which was conducted to evaluate the prevalence of structural and functional abnormalities within the spinal cord in patients with clinically normal neurologic condition. In all patients the clinical diagnosis and intact neurological condition was ascertained by a spinal orthopedic surgeon. Full-length spinal axis MRI studies (T1/T2 sequences) and SSEPs of the tibial nerves (tSSEPs) were pre-operatively examined by independent evaluators blinded to the patients' medical histories. Structural spinal cord abnormalities were found in 3 of 100 AIS patients on MRI. In 1 patient a Chiari malformation type 1 with an accompanying syringomyelia was diagnosed, which required a suboccipital decompression. In the other 2 patients small thoracic syringomyelias were diagnosed. Abnormalities of spinal cord function were detected in 68 % of the 100 patients: tSSEP latencies corrected for body height were increased in 56 % of the patients; pathological differences between tSSEPs on the left and right sides were present in 17 % (12 % in combination with a prolongation of the latency). The authors concluded that the findings of this study indicated that MRI and electrophysiological examinations are essential to evaluate spinal cord abnormalities that are clinically not detectable in AIS patients. Even in patients with intact neurologic condition and clinically typical right-curved thoracic scoliosis, the possibility of intra-spinal pathologies should be ruled out by MRI. It is especially important to detect structural pathologies like syringomyelia and Chiari malformation before proceeding with scoliosis surgery, as these conditions are associated with a higher neurological risk during scoliosis surgery. The electrophysiological recordings made in the present study, with the high number of pathological tSSEPs, are indicative of functional abnormalities with a sub-clinical involvement of the recorded neuronal pathways. The relevance of the latter findings is not yet clear, but pre-operative tSSEP examinations offer the possibility of evaluating alterations in spinal cord function that are undetectable by clinical examination.

Virk et al (2019) stated that intra-operative neuromonitoring is well established and widely used to assist in completing corrective surgery for AIS safely. The role of pre-operative measurement of SSEPs and/or transcranial magnetic stimulation (TMS) to determine if there is trans-spinal pathology, however, is unclear. These researchers examined if pre-operative SSEP and/or TMS measurement provided clinical benefit to patients with AIS. They carried out a review of medical charts between 2010 and 2012 for patients who underwent surgery for scoliosis; patients with diagnoses other than AIS were excluded. Patients with incomplete pre-operative or intra-operative data were also excluded. Relevant clinical information such as age, sex, number of levels fused, and major Cobb angle were recorded. Pre-operative neuromonitoring measurements and intra-operative neuromonitoring results were reviewed by an attending neurologist. Any instance in which an intra-operative surgical plan or neuromonitoring result interpretation was influenced by pre-operative results was recorded. Further imaging obtained based on pre-operative results was noted. Any acute neurologic complication such as paralysis was noted. A total of 81 patients met inclusion criteria (64 female, 17 male); average age was 15 years (± 1.92). Major Cobb angle at pre-operative evaluation averaged 57.5 degrees (± 10.81 degrees); 10 patients had abnormal pre-operative SSEP/TMS results. There were no changes in protocol during intra-operative neuromonitoring based upon pre-operative neuromonitoring findings. No additional imaging was needed for patients with abnormal pre-operative neuromonitoring results. There was no statistically significant difference in pre-operative Cobb angle between the group of patients with abnormal pre-operative neuromonitoring and those with normal baseline testing. The authors concluded that pre-operative SSEP/TMS measurement prior to corrective surgery for AIS has limited utility. There were no instances in which a patient's clinical course was improved by testing. These investigators recommended against routine use of preoperative SSEP/TMS testing for AIS patients requiring corrective surgery.

Furthermore, an UpToDate review on “Adolescent idiopathic scoliosis: Management and prognosis” (Scherl, 2021) states that “The preoperative evaluation for scoliosis surgery includes posteroanterior and lateral spinal radiographs and pulmonary function tests for patients with curves ≥ 60°. Lateral bending films for surgical planning may be obtained at the discretion of the surgeon”. It does not mention pre-operative SSEP.

Vestibular Evoked Myogenic Potential (VEMP) for Evaluation of Members with Bilateral Sensorineural Hearing Loss after Cochlear Implantation

Abouzayd et al (2017) noted that vestibular function after cochlear implantation (CI) is difficult to understand, as subjective vestibular symptoms appeared uncorrelated with the results of objective tests. Consequently, clinicians may struggle to decide what assessments to perform for a symptomatic patient. These investigators carried out a systematic review and meta-analysis approach to enlighten this point. After a study inclusion process, results were classified into 4 different groups for each test in each study: (i) 'true positive' if the test showed impairment from pre-operative to post-operative in symptomatic patients; (ii) 'false positive' if the test showed impairment from pre-operative to post-operative in asymptomatic patients; (iii) 'true negative' if the test showed no impairment in asymptomatic patients; and (iv) 'false negative' if the test showed no impairment in symptomatic patients. From these groups, sensitivities and specificities of each test were calculated in a meta-analysis. After reviewing more than 3,000 references, 16 studies were included, representing 957 patients. The meta-analysis revealed a sensitivity of 0.21 (95 % CI: 0.08 to 0.40) for the caloric tests, of 0.32 (95 % CI: 0.15 to 0.54) for the cervical vestibular evoked myogenic potentials (c-VEMP), and of 0.5 (95 % CI: 0.07 to 0.93) for the head impulse tests (HITs). The analysis of prevalence revealed that c-VEMPs were the most often impaired, and the HIT the most often conserved. The authors concluded that this review and meta-analysis revealed that no vestibular test is sensitive enough to be recommended as a single test. Ideally, all the 5 vestibular sensors should be tested. In clinical practice, these investigators suggested a case-to-case strategy according to patient's symptoms and their suspected origin.

Hansel et al (2018) stated that post-operative vertigo is a common complaint after CI; but published incidence rates differ vastly. In a meta-analysis, these investigators examined both subjective complaints of vertigo before and after CI and related vestibular diagnostic tests on CI candidates. They carried out a systematic literature search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement in PubMed, Cochrane Register, and Embase. These researchers presented 116 eligible studies examining subjective complaints of vertigo after CI and/or related vestibular diagnostic tests. They performed 3 meta-analyses of 46 eligible studies with matched pre- and post-operative data to calculate the odds ratio (OR) of new vertigo onset, as well as the impairment of vestibular receptors measured by nystagmography and c-VEMP. Post-operative vertigo was calculated from 95 studies and further subdivided by mean age with pooled data. These investigators observed a significant increase in post-operative vertigo and significant impairment of nystagmography and c-VEMP detection. Vertigo after CI was reported in 9.3 % of the patients with a continuous increase in patient age at surgery. In a subgroup of studies, new onset of vertigo was found in 17.4 % of the patients. Furthermore, 7.2 % of the patients had persisting vertigo complaints, whereas 11.6 % described an altered vertigo quality and 7.7 % had their pre-operative complaints resolved. A comparison of round window approach and cochleostomy revealed significantly increased vertigo after cochleostomy. Both insertion methods showed similar effects in nystagmography and c-VEMP testing. The authors concluded that CI had a significant impact on subjective vertigo and vestibular receptor function. This was affected by the patient's age at the time of surgery. The surgical technique (round window or cochleostomy) may influence the outcome; however, this requires further investigation. Younger patients may compensate better following vestibular dysfunction; and peri-operative testing is needed to correlate vestibular impairment and subjective complaints.

Yong et al (2019) noted that CI could result in post-operative vestibular dysfunction of unknown clinical significance. These researchers characterized the presence, magnitude, and clinical significance of vestibular dysfunction that occurs after pediatric CI. The databases Embase, Medline (OvidSP), and PubMed were used. Only articles published in English were included. Grey literature and unpublished sources were also reviewed. Articles published from 1980 until the present that documented pre-operative and post-operative vestibular testing on children under the age of 18 years were used. Parameters that were assessed included number of patients, pre- and post-operative vestibular-evoked myogenic potentials (VEMPs), HIT, caloric testing, and posturography, timing of pre- and post-operative testing, symptomatology, and other demographic data such as etiology of the hearing loss. A total of 10 articles were included. Relative risk (RR) values examining the effect of CI on vestibular function were calculated for VEMPs and caloric testing due to the availability of published data. I2 values were calculated; and 95 % CIs were reported. Separate analyses were conducted for each individual study and a pooled analysis was conducted to yield an overall relative risk. Assessment on risk of bias in individual studies and overall was performed. The authors concluded that pediatric CI was associated with a statistically significant decrease in VEMP responses post-operatively (RR 1.8, p < 0.001, I2 91.86, 95 % CI: 1.57 to 2.02). Similar results were not observed in caloric testing. Insufficient data is available for analysis of HIT and posturography. These researchers stated that further studies are needed to determine the effect of CI on objective vestibular measures post-operatively and whether any changes observed are clinically relevant in this population.

In a prospective, case-series study, Li and Gong (2020) examined the effects of unilateral CI on otolith function by observing the changes in ocular VEMP (o-VEMP) and c-VEMP in children. The o-VEMP and c-VEMP elicited by air-conducted sound in 35 children were analyzed pre-operatively and at 5 days, 1 month, and 2 months after surgery. Before CI, the response rates of o-VEMPs and c-VEMPs were 81.4 % and 91.4 %, respectively. In the implanted side, o-VEMPs and c-VEMPs were reduced by 37.1 % and 68.6 %, respectively, 5 days after CI. One month after CI, o-VEMPs and c-VEMPs were 34.6 % and 72 %, respectively, with the device switched off, and 50 % and 73.1 %, respectively, with the device switched on. Two months after CI, the o-VEMPs and c-VEMPs were 36 % and 80 %, respectively, when the implant was turned off, and 70.8 % and 75 %, respectively, when the implant was turned on. The authors concluded that the findings of this study confirmed the value of VEMP testing in the clinical setting and that absent VEMPs could indicate impairment of otolith function after CI.

West et al (2021) noted that CI may be complicated by concurrent injury to the vestibular apparatus, potentially resulting in disabling vertigo and balance problems. Information on vestibular function before implantation as measured by the video HIT (vHIT) and c-VEMPs is scarce and literature on long-term effects is non-existing. In a retrospective repeated measurement study, these researchers examined how vestibular function was affected by CI, as measured by vHIT and c-VEMPs in the late phase after implantation. Among the 436 patients elected for CI surgery during 2013 to 2018, 45 patients met the inclusion criteria (CI recipients with a vestibular assessment before the first CI and a repeated vestibular assessment after the CI operation). vHIT and c-VEMPs were measured before and after CI. Main outcome measures were vestibular function as evaluated by vHIT gain, saccades and c-VEMPs. The mean time between 1st and 2nd vestibular screening was 19 months. The mean vHIT gain on implanted ears was 0.79 before the operation and showed no change at follow-up (p = 0.65). Likewise, the number of abnormal vHIT gain values was equal before and after the operation (p = 0.31). Pre-operatively, saccades were present on 12 ears (14 %) compared with 25 ears (29 %) post-operatively (p = 0.013) and were associated with significantly lower vHIT gain values. Pre-operatively, positive c-VEMPs were found in 20 CI ears (49 %) and 24 contralateral ears (62 %); 10 CI ears lost c-VEMP post-operatively compared with 2 ears on the contralateral side (p = 0.0047). The authors concluded that even though vHIT gain has been reported to be affected in the immediate post-implantation period, the findings in this study showed that vHIT gain was normalized in the long-term. However, CI was associated with the occurrence of vHIT saccades in the long-term and these were associated with lower vHIT gain values. Furthermore, c-VEMP responses were significantly reduced long-term on implanted ears, which agreed with other studies with shorter follow-up.

Gerdsen et al (2022) provided a scoping review of the available literature for determining objectively the effect of CI on vestibular function in children. These researchers carried out a literature search and the following criteria were used: vestibular tests that were performed on subjects within the range of 0 to 18 years old before and after CI. The papers conducted at least 1 of the following tests: (video) HIT, caloric test, c-VEMP and o-VEMP or rotatory chair test. Included papers underwent quality assessment and this was graded by risk of bias and directness of evidence. A total of 14 articles met the selection criteria. The included studies showed that CI resulted in a decrease in vestibular function in a proportion of the patient population. This loss of vestibular function can be permanent, but (partial) restoration over the course of months to years is possible. The pooling of data determined that the articles varied on multiple factors, such as time of testing pre- and post-operatively, age of implantation, etiologies of hearing loss, used surgical techniques, type of implants and the applied protocols to determine altered responses within vestibular tests. The overall quality of the included literature was deemed as high risk of bias and medium-to-low level of directness of evidence; thus, the data was considered not feasible for systematic analysis. The authors concluded that this review implicated that vestibular function was either unaffected or showed short-term or permanent deterioration after CI in children. However, the heterogeneity of the available literature indicated the importance of standardized testing to improve the knowledge of the effect of CI on the vestibular function and subsequent developmental consequences for the concerned children.

Wu et al (2022) stated that vestibular dysfunction may delay the achievement of balance and perception milestones in pediatric patients after CI. These investigators carried out a strategic literature search following the PRISMA guidelines. They searched the PubMed, Medline, Embase, Web of Science, and Cochrane Library databases from inception to July 2022. Studies were included on the otoliths, semicircular canals, and balance function changes in children after CI. Two reviewers independently examined the level of evidence, methodological limitations, risk of bias, and characteristics of the cases. Matched pre- and post-operative vestibular functional test data, including o-VEMP and c-VEMP, caloric test, vHIT, and Bruininks-Oseretsky Test 2 (BOT-2), were used to calculate the relative risk of vestibular disorders. Subgroup analyses were performed according to surgical approach, CI device status, and etiology. A total of 20 studies that met the inclusion criteria were selected for the meta-analysis. These investigators observed significant vestibular dysfunction in pediatric patients with CI. The results showed a statistically significant increase in abnormal c-VEMP response (RR = 2.20, 95 % CI: 1.87 to 2.58, p < 0.0001), abnormal o-VEMP response (RR = 2.10, 95 % CI: 1.50, 2.94, p < 0.0001), and abnormal caloric test results (RR = 1.62, 95 % CI: 1.20 to 2.19, p = 0.0018) after CI. Statistically significant differences were not observed in the vHIT test results of all 3 semicircular canals before and after the operation (p > 0.05). Regarding static and dynamic balance, these researchers found significantly poorer BOT-2 scores in children with CI than in the normal group (mean difference [MD] = -7.26, 95 % CI: -10.82 to -3.70, p < 0.0001). The authors concluded that the results of this systematic review and meta-analysis showed that vestibular dysfunction might occur after CI in pediatric patients. Some children experienced difficulties with postural control and balance. These investigators stated that these findings suggested that a comprehensive evaluation of vestibular function should be performed before and after CI.

Glossary of Terms

Table: Glossary of Terms
Term	Definition
Brainstem Auditory Evoked Potential (BAEP)	Monitors the function of the auditory nerve and auditory pathways in the brainstem
Electroencephalography (EEG)	The electrical activity measured by EEG is generated by groups of pyramidal neurons, which has cell bodies in the 3rd and 5th layer of the cerebral cortex.
Electromyography (EMG)	Monitors somatic efferent nerve activity and evaluates the functional integrity of individual nerves. Monitors intracranial, spinal, and peripheral nerves during surgeries.
Motor Evoked Potential (MEP)	Monitors motor pathways, transcranial electrical stimulation elicits excitation of corticospinal projections at multiple levels
Somatosensory Evoked Potential (SSEP)	Monitors the dorsal column–medial lemniscus pathway, which mediates tactile discrimination, vibration, and proprioception. Stimulation of sensory receptors in the skin initiates peripheral sensory nerves, which extend through the nerve root to the ipsilateral dorsal root ganglia at spinal levels.
Visual Evoked Potential (VEP)	Measures the functional integrity of the optic pathways from the retina to the brain's visual cortex in response to light stimulus. Visual stimulus is converted into nerve signals in the retina. These signals are transmitted via the optic pathway to the brain, from the retina to the optic nerve, optic chiasma, optic tract, lateral geniculate body, optic radiation, and visual cortex occipital lobe.

Source: Ghatol and Widrich, 2022

Appendix

Documentation Requirements

All medical necessity criteria must be clearly documented in the member's medical record and made available upon request.
The member's medical record must contain documentation that fully supports the medical necessity for evoked potential studies. This documentation includes, but is not limited to, relevant medical history, physical examination, the anatomic location of the planned surgical procedure, the rationale for the location and modalities to be monitored, and results of pertinent diagnostic tests or procedures.
For the BAERs, the member’s medical record should document the otologic exam describing both ear canals and tympanic membranes, as well as a gross hearing assessment. The medical record should also include the results of air and bone pure tone audiogram and speech audiometry.
The physician’s evoked potential report should note which nerves were tested, latencies at various testing points, and an evaluation of whether the resulting values are normal or abnormal.
Baseline testing prior to intraoperative neuromonitoring requires contemporaneous interpretation prior to the surgical procedure. To qualify for coverage of baseline testing, results of testing of multiple leads for signal strength, clarity, amplitude, etc., should be documented in the medical record. The time spent performing or interpreting the baseline electrophysiologic studies performed prior to surgery should not be counted as intraoperative monitoring, but represents separately reportable procedures. Testing performed during surgery does not qualify as baseline testing and is not a separately reportable procedure.

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The above policy is based on the following references:

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Last Review 10/11/2024

Effective: 11/13/1997

Next Review: 02/13/2025
Review History
Definitions

Evoked Potential Studies

Table Of Contents

Policy

Scope of Policy

Medical Necessity

Evoked Potential Studies

Somatosensory evoked potentials (SEPs, SSEPs) or dermatosensory evoked potentials (DSEPs)

Visual Evoked Potentials (VEPs)

Brain Stem Auditory Evoked Response (BAER)

Cervical Vestibular Evoked Myogenic Potential (cVEMP)

Experimental, Investigational, or Unproven

Related Policies

CPT Codes / HCPCS Codes / ICD-10 Codes

Somatosensory evoked potentials (SEPs, SSEPs):

CPT codes covered if selection criteria are met:

ICD-10 codes covered if selection criteria are met:

ICD-10 codes not covered for indications listed in the CPB (not all-inclusive):

Visual evoked potentials (VEPs):

CPT codes covered if selection criteria are met:

CPT codes not covered for indications listed in the CPB:

ICD-10 codes covered if selection criteria are met (for members > 3 mos of age):

ICD-10 codes not covered for indications listed in the CPB (for members > 3 mos of age) (not all-inclusive):

ICD-10 codes not covered for indications listed in the CPB (for members < 3 mos of age/ neonatal screen):

Brain stem auditory evoked response (BAER), comprehensive:

CPT codes covered if selection criteria are met:

ICD-10 codes covered if selection criteria are met (members > 3 mos of age):

ICD-10 codes not covered for indications listed in the CPB (members > 3 mos of age) (not all-inclusive):

ICD-10 codes not covered for indications listed in the CPB (for members < 3 mos of age/ neonatal screen):

Brain stem auditory evoked response (BAER), limited:

CPT codes covered if selection criteria are met:

ICD-10 codes covered if selection criteria are met:

ICD-10 codes not covered for indications listed in the CPB:

Cervical vestibular myogenic potential (cVEMP):

CPT codes covered if selection criteria are met:

ICD-10 codes covered if selection criteria are met:

Evoked otoacoustic emissions:

CPT codes covered if selection criteria are met:

ICD-10 codes not covered for indications listed in the CPB (for comprehensive exam only for members < 3 mos. of age/ neonatal screen):

ICD-10 codes covered for indications listed in the CPB not all inclusive (for screening exam only for members < 3 yrs. of age):

ICD-10 codes not covered for indications listed in the CPB (for screening exam only for members < 3 yrs. of age):

Motor evoked potentials (other than intraoperative with SSEPs):

CPT codes not covered for indications listed in the CPB:

ICD-10 codes not covered for indications listed in the CPB:

Vestibular evoked myogenic potentials (VEMP):

CPT codes not covered for indications listed in the CPB:

ICD-10 codes not covered for indications listed in the CPB:

Evoked cortical potentials associated with transcranial magnetic stimulation:

CPT codes not covered for indications listed in the CPB:

Background

Loudness-Dependence of Auditory Evoked Potentials

Motor Evoked Potentials for Evaluation of Wilson's Disease

Somatosensory Evoked Potentials as Prognostic Tests in Neonates with Hypoxic-Ischemic Encephalopathy

Visual Evoked Potentials for Evaluation of Birdshot Chorioretinopathy

Motor Evoked Potentials for Evaluation of Wilson's Disease

Ocular Vestibular Evoked Myogenic Potentials for the Diagnosis of Myasthenia Gravis

Vestibular Evoked Myogenic Potentials for the Diagnosis of Meniere's Disease or Delayed Endolymphatic Hydrops

Cervical and Ocular Vestibular Evoked Myogenic Potential Testing

Visual Evoked Potential for Evaluation of Neuromyelitis Optica Spectrum Disorder

Auditory Evoked Potential for Evaluation of Hearing and Language Deficits in Survivors of Extracorporeal Membrane Oxygenation

Ocular Vestibular Evoked Myogenic Potentials for Diagnosis of Myasthenia Gravis

Short-Latency Somatosensory Evoked Potential (SSEP) Study for Evaluation of Movement Disorders

Cervical Vestibular Evoked Myogenic Potential (cVEMP) for the Evaluation of Vertigo

Ocular Vestibular Evoked Myogenic Potential (oVEMP) for the Diagnosis of Benign Paroxysmal Positioning Vertigo

Olfactory Event‐Related Potential for the Evaluation of Long-Term COVID-19

Pre-Operative SSEP of the Bilateral Tibial Somatosensory Pathways Prior To Scoliosis Surgery

Vestibular Evoked Myogenic Potential (VEMP) for Evaluation of Members with Bilateral Sensorineural Hearing Loss after Cochlear Implantation

Glossary of Terms

Appendix

Documentation Requirements

References

Policy History

Additional Information