Optic Nerve Decompression Surgery

Number: 0415

Table Of Contents

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

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Policy

Scope of Policy

This Clinical Policy Bulletin addresses optic nerve decompression surgery.

1. Medical Necessity

   Aetna considers optic nerve decompression surgery medically necessary for the treatment of the following indications:

   1. Papilledema accompanying pseudotumor cerebri (idiopathic intracranial hypertension)
   2. Progressive visual loss associated with craniofacial fibrous dysplasia
   3. Secondary intracranial hypertension with cerebrovenous sinus thrombosis.

2. Experimental and Investigational

   Aetna considers optic nerve decompression surgery experimental and investigational for the following indications (not an all-inclusive list) because of insufficient evidence in the peer-reviewed literature:

   1. Intermittent paroxysmal unilateral phosphenes (i.e., light flashes) associated with worsening visual field defects
   2. Non-arteritic anterior ischemic optic neuropathy (NAION)
   3. Optic nerve sheath or parasellar meningiomas
   4. Traumatic optic neuropathy and non-traumatic compressive optic neuropathy
   5. Visual loss secondary to optic nerve drusen.

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Table:

CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
CPT codes covered if selection criteria are met:
67570	Optic nerve decompression (e.g., incision or fenestration of optic nerve sheath)
CPT codes not covered for indications listed in the CPB (not all-inclusive):
31294	Nasal/sinus endoscopy, surgical, with optic nerve decompression
ICD-10 codes covered if selection criteria are met:
G93.2	Benign intracranial hypertension
H47.11	Papilledema associated with increased intracranial pressure
I67.6	Nonpyogenic thrombosis of intracranial venous system [Secondary intracranial hypertension with cerebro-venous sinus thrombosis]
ICD-10 codes not covered for indications listed in the CPB:
D33.3	Benign neoplasm of cranial nerves [optic nerve sheath or parasellar meningiomas]
H47.011 - H47.019	Ischemic optic neuropathy [non-arteritic anterior ischemic optic neuropathy (NAION)]
H47.091 - H47.099	Other disorders of optic nerve, not elsewhere classified [non-traumatic compressive optic neuropathy]
H47.321 - H47.329	Drusen of optic disc
H53.8	Other visual disturbances [Intermittent paroxysmal unilateral phosphenes (i.e., light flashes)]
S04.011A - S04.019S	Injury of optic nerve

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Background

Optic nerve decompression surgery (also known as optic nerve sheath decompression surgery) involves cutting slits or a window in the optic nerve sheath to allow cerebrospinal fluid to escape, thereby reducing the pressure around the optic nerve.

Pseudotumor cerebri (also known as idiopathic intracranial hypertension) is a syndrome of increased intracranial pressure without a discernable cause.  There is a distinct female preponderance from the teens through the fifth decade.  If medical treatment has failed (i.e., Diamox, Lasix, corticosteroids), and disc swelling with visual field loss progresses, direct fenestration of the optic nerve sheaths via medial or lateral orbitotomy has been shown to be an effective and relatively simple procedure for relief of papilledema.

Non-arteritic anterior ischemic optic neuropathy (NAION) is a common cause of sudden loss of vision, especially in the elderly.  It is caused by infarction of the short posterior ciliary arteries supplying the anterior optic nerve.  There is no direct treatment for NAION, although corticosteroids are sometimes used to reduce optic nerve edema.  Treatment goals are aimed at controlling the systemic vascular disease (i.e., hypertension, diabetes, and atherosclerosis) or collagen vascular disease that precipitated NAION in hopes of preventing or delaying bilateral involvement.

Initial results of uncontrolled studies suggested that optic nerve sheath decompression was a promising treatment of progressive visual loss in patients with NAION.  Other investigators who evaluated this surgical procedure reported varying degrees of success.  To resolve the controversy over the effectiveness of optic nerve decompression for NAION, the National Eye Institute sponsored the Ischemic Optic Neuropathy Decompression Trial, a multicenter, randomized controlled clinical trial of optic nerve decompression surgery for patients with NAION.  The study found no benefit from surgery in NAION patients with progressive visual loss; in fact, significantly more patients in the surgery group had progressive loss of vision than patients who received only careful follow-up.  The investigators concluded that optic nerve decompression surgery is not an effective treatment for NAION, and in fact, may increase the risk of progressive visual loss in NAION patients.

A structured evidence review (Dickersin and Manheimer, 2002) concluded that “[r]esults from the Ischemic Optic Neuropathy Decompression Trial indicate that optic nerve decompression surgery for nonarteritic ischemic optic neuropathy is not effective."

A Cochrane review (Dickersin et al, 2012) concluded that results from the single trial indicate no evidence of a beneficial effect of optic nerve decompression surgery for NAION.  Pletcher and associates (2006) stated that the indications and outcomes for endoscopic decompression of the optic nerve remain controversial.

Atkins et al (2010) stated that NAION is the most common clinical presentation of acute ischemic damage to the optic nerve.  Most treatments proposed for NAION are empirical and include a wide range of agents presumed to act on thrombosis, on the blood vessels, or on the disk edema itself.  Others are presumed to have a neuroprotective effect.  Although there have been multiple therapies attempted, most have not been adequately studied, and animal models of NAION have only recently emerged.  The Ischemic Optic Neuropathy Decompression Trial, the only class I large multi-center prospective treatment trial for NAION, found no benefit from surgical intervention.  One recent large, non-randomized controlled study suggested that oral steroids might be helpful for acute NAION.  Others recently proposed interventions are intra-vitreal injections of steroids or anti-vascular endothelial growth factor (anti-VEGF) agents.  There are no class I studies showing benefit from either medical or surgical treatments.  Most of the literature on the treatment of NAION consists of retrospective or prospective case series and anecdotal case reports.  Similarly, therapies aimed at secondary prevention of fellow eye involvement in NAION remain of unproven benefit.

Traumatic optic neuropathy (TON) is a complication of head trauma; and there is no uniformly accepted treatment protocol for this condition.  Endoscopic, minimally invasive decompression of the optic nerve in its bony canal ihas been used as an alternative to conservative approach.  Sieskiewicz et al (2008) performed endoscopic optic nerve decompression in 6 patients with blindness or severe impairment of vision caused by head trauma.  In 5 of them, direct optic nerve injury might have been suspected due to presence of bony fractures in the region of the optic canal and the orbital apex.  The time from the trauma to the surgical intervention varied from 8 hours to 30 days.  All patients were treated with steroids before the attempted surgery, however the doses and time of this treatment varied significantly.  There were no complications of the surgery; patients were mobilized on the day of operation and reported no problems with nasal breathing.  Improvement in vision was observed in only 2 of 6 patients (33.3 %).

In a retrospective study, Wang and associates (2008) examined the effectiveness of endoscopic optic nerve decompression in patients with TON.  Patients (n = 46) were first treated with methylprednisolone for 6 days.  Forty-four patients (46 eyes) who did not improve with methylprednisolone treatment were offered endoscopic optic nerve decompression.  In 38 eyes with no light perception vision pre-operatively, 21 eyes (45.6 %) had improvement in visual acuity.  These patients had post-operative light perception in 17 eyes, hand movement in 3 eyes and 60/200 in 1 eye.  Four of 5 eyes with light perception pre-operatively had post-operative vision for hand movement in 2 eyes, finger counting in 1 eye and 20/200 in 1 eye.  For 3 eyes with pre-operative visual acuity of hand movement, the post-operative visual acuities were 60/200, 60/200 and 120/200.  Neither worsening of vision nor major complications was encountered in this series.  The authors concluded that endoscopic optic nerve decompression in experienced surgeons' hands can improve visual acuity in TON with minimal morbidity.

On the other hand, Li et al (2008) reported that there were no difference (statistically) between steroids and steroids plus optic nerve decompression in treating TON.  A total of 237 patients were treated with steroids; 176 also consented to endoscopic optic nerve decompression.  The total vision improvement rate was 55 % in the 176 patients treated with both steroids and endoscopic optic nerve decompression, compared with 51 % in the 61 patients treated with steroids alone; this difference was not statistically significant (p > 0.05).

Wu and co-workers (2008) stated that serious injury to the optic nerve, including direct and indirect events, induces significant visual loss and even blindness.  For the past decade corticosteroids and/or optic canal decompression surgery have been widely embraced as therapeutic paradigms for the treatment of TON.  However, the authors noted that there is little clinical evidence to support the effectiveness of these strategies, raising questions about the efficiency of current therapy for improving visual outcomes.

A Cochrane systematic evidence review (Yu Wai Man and Griffith, 2005; Yu Wai Man and Griffith, 2007) found no randomized controlled trials for either the use of corticosteroids or surgical treatment for traumatic optic neuropathy.  Citing reports of visual recovery rates of 40 to 60 % with conservative management, the authors concluded that the decision to proceed with surgery or high-dose corticosteroids depends on the clinical judgment and surgical skills of the surgeon as well as informed consent of the patient to appreciate the benefits and risks of both treatments.  More recently, a randomized a placebo-controlled trial of the use of intravenous high-dose corticosteroids versus saline in 31 patients with traumatic optic neuropathy (Entezari et al, 2007) found no statistically significant improvement in visual acuity between the 2 groups.

The International Optic Nerve Trauma Study was organized to compare corticosteroids or surgery and corticosteroids, but after failure to enroll sufficient numbers of patients, the study was transformed into an observational study.  Comparing no treatment (observation) versus corticosteroids or surgical decompression, the authors found no difference in the final visual acuity and commented that the decision to treat or not treat should be made on an individual patient basis (Levin et al, 1999). 

Some authorities have recommended optic canal decompression if visual acuity does not improve to 20/400 or better despite 24 to 48 hours of steroid therapy or if visual acuity is 20/200 or better but deteriorates during or after completion of steroid therapy (Kountakis et al, 2000).

In a Cochrane review, Dickersin et al (2012) evaluated the safety and effectiveness of surgery compared with other treatment or no treatment in people with NAION.  These investigators searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 11), MEDLINE (January 1950 to November 2011), EMBASE (January 1980 to November 2011), the metaRegister of Controlled Trials, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform.  There were no date or language restrictions in the electronic searches for trials.  The electronic databases were last searched on November 19, 2011.  All randomized trials of surgical treatment of NAION were eligible for inclusion in this review.  These researchers obtained full copies of all potentially relevant articles.  One author extracted data which was verified by another author.  No data synthesis was required.  The 1 included trial randomized 258 participants and was stopped early for futility.  At the time of the 24-month report the follow-up rate was 95.3 % for 6 months and 67.4 % for 24 months (174 participants; 89 careful follow-up and 85 surgery).  There was no evidence of a benefit of surgery on visual acuity.  Measurements of visual acuity and visual fields were performed by a technician masked to the treatment received.  At 6 months 32.0 % of the surgery group had improved visual acuity by 3 or more lines compared with 42.6 % of the careful follow-up group (unadjusted relative risk (RR) 0.75, 95 % confidence interval (CI): 0.54 to 1.04).  At 24 months 29.4 % of the surgery group had improved compared with 31.0 % of the careful follow-up group (unadjusted RR 0.95, 95 % CI: 0.60 to 1.49).  Participants who underwent surgery had a greater risk of losing 3 or more lines of vision, although the increased risk was not statistically significant.  At 6 months 18.9 % in the surgery group had worsened compared with 14.8 % in the careful follow-up group (RR 1.28; 95 % CI: 0.73 to 2.24).  At 24 months 20.0 % in the surgery group had worsened compared with 21.8 % in the careful follow-up group (RR 0.92; 95 % CI: 0.51 to 1.64).  Participants who received surgery experienced both intra-operative and post-operative adverse events, including central retinal artery occlusion during surgery and light perception vision at 6 months (1 participant); and immediate loss of light perception following surgery and loss of vision that persisted to the 12-month visit (2 participants).  In the careful follow-up group, 2 participants had no light perception at the 6-month follow-up visit; 1 of these had improved to light perception at 12 months.  Pain was the most common adverse event in the surgery group (17 % in surgery group versus 3 % in the careful follow-up group at 1 week).  Diplopia (double-vision) was the next most common complication (8 % in the surgery group versus 1 % in the careful follow-up group at 1  week); at 3 months there was no statistically significant difference in proportion of participants with diplopia between the 2 groups.  The authors concluded that results from the single trial indicate no evidence of a beneficial effect of optic nerve decompression surgery for NAION.  They stated that future research should focus on increasing the understanding of the etiology and prognosis of NAION; new treatment options should be examined in the context of randomized clinical trials.

Moreau et al (2014) examined the safety and effectiveness of optic nerve sheath decompression (ONSD) with a medial trans-conjunctival approach for a variety of indications in a larger population of patients than has previously been reported.  A retrospective chart review was performed on consecutive patients who underwent ONSD between January 1992 and December 2010.  Before ONSD, all patients had documented evidence of progressive loss of visual acuity or visual field, or both.  Post-operative follow-up visits were scheduled at 1 week, 1 month, and then every 3 to 6 months.  Main outcome measures were visual acuity, visual fields, and surgical complications.  A total of 578 eyes of 331 patients underwent ONSD for progressive vision loss due to various indications, which included but were not limited to idiopathic intracranial hypertension (IIH), progressive NAION, and optic nerve drusen (OND).  During a mean follow-up of 18.7 months (range of 1 week to 10 years), post-operative visual acuity remained stable or improved in 536 of 568 eyes (94.4 %) and progressively worsened in 32 of 568 eyes (5.6 %).  Visual fields remained stable or improved in 257 of 268 eyes (95.9 %) and progressive visual field loss occurred in 11 of 268 eyes (4.1 %).  There were no reported intra-operative complications.  The most common post-operative complication was diplopia (6.0 %).  The authors concluded that this review represented the largest series of patients who have undergone ONSD for any indication.  These data were consistent with current literature supporting ONSD as a safe and effective procedure for IIH.  Other indications for ONSD, such as progressive visual field loss associated with OND, warrant further study.  Regardless of the indication, complications following ONSD with the technique described in this report were infrequent.

Intermittent Paroxysmal Unilateral Phosphenes

De Ridder et al (2016) stated that microvascular decompression surgery is standard neurosurgical practice for treating trigeminal neuralgia and hemi-facial spasm. Most other cranial nerves have been decompressed for paroxysmal intermittent hyperactivity of the affected cranial nerve or in very long-standing compressions to treat cranial nerve hypo-functioning.  These investigators described a case of intermittent paroxysmal unilateral phosphenes (i.e., light flashes) associated with worsening visual field defects.  Magnetic resonance imaging showed a sandwiched optic nerve/chiasm between an inferior compression of the internal carotid artery and a superior compression of the anterior communicating artery.  The patient was successfully treated by microvascular decompression and anterior clinoidectomy plus optic canal un-roofing.  The authors concluded that this case report added to the few previous case reports combining 2 previously described techniques (i.e., microvascular decompression and anterior clinoidectomy plus optic canal un-roofing).  The major drawbacks of this study were that it was a single-case study and its findings were confounded by the combinational use of microvascular decompression and anterior clinoidectomy plus optic canal un-roofing.

Progressive Visual Loss Associated with Craniofacial Fibrous Dysplasia

Bhattacharya and Mishra (2015) stated that fibrous dysplasia (FD) is a non-malignant fibro-osseous bony lesion in which the involved bone/bones gradually get converted into expanding cystic and fibrous tissue.  The underlying defect in FD is post-natal mutation of GNAS1 gene, which leads to the proliferation and activation of undifferentiated mesenchymal cells arresting the bone development in woven phase and ultimately converting them into fibro-osseous cystic tissue.  Cherubism is a hereditary form of fibrous dysplasia in which the causative factor is transmission of autosomal dominant SH3BP2 gene mutation.  The disease may present in 2 distinct forms:

1. a less severe and limited monostotic form, and
2. a more aggressive and more widespread polyostotic form.

Polyostotic form may be associated with various endocrine abnormalities, which require active management apart from the management of FD.  Management of FD is not free from controversies.  While total surgical excision of the involved area and reconstruction using newer micro-vascular technique is the only definitive treatment available from the curative point of view, but this can be only offered to monostotic and very few polyostotic lesions.  In polyostotic varieties on many occasions these radical surgeries are very deforming in these slow growing lesions and so their indication is highly debated.  The treatment of craniofacial FD should be highly individualized, depending on the fact that the clinical behavior of lesion is variable at various ages and in individual patients.  A more conservative approach in the form of aesthetic re-contouring of deformed bone, orthodontic occlusal correction, and watchful expectancy may be the more accepted form of treatment in young patients.  Newer generation real-time imaging guidance during re-contouring surgery adds to accuracy and safety of these procedures.  Regular clinical and radiological follow-up is needed to watch for quiescence, regression or reactivation of the disease process.  Patients must be warned and watched for any sign of nerve compression, especially visual impairment due to optic nerve compression.  Rather than going for prophylactic optic canal decompression (which does more harm than good), optic nerve decompression should be done in symptomatic patients only, and preferably be done via minimal invasive endoscopic neurosurgical approach than the conventional more morbid open craniotomy approach.  The authors noted that there is growing research and possibilities that newer generation bisphosphonate medication may change the management scenario, as these medications show encouraging response in not only reducing the osteoclastic activity, but simultaneously also stimulating the osteoblastic and osteocytic activities.

Belsuzarri and associates (2016) noted that FD is a benign fibro-osseous lesion related to an abnormal bone development and replacement by fibrous tissue.  Fibrous dysplasia has 3 clinical patterns:

1. monostotic,
2. polyostotic, and
3. the McCune-Albright syndrome (MAS).

McCune-Albright syndrome is a rare genetic disorder (about 3 % of all FDs) that comprises a triad of polyostotic FD, cafe-au-lait skin macules, and precocious puberty; MAS can involve the orbit region and cause stenosis in the optic canal, leading the patient to a progressive visual loss.  These investigators reported a case of craniofacial FD in MAS in a 9-year old male with progressive visual loss, submitted to optic nerve decompression by fronto-orbito-zygomatic approach, with total recovery.  A research was made at Bireme, PubMed, Cochrane, LILACS, and Medline with the keywords: FD/craniofacial/McCune-Albright/Optic compression for the clinical review.  A clinical review of the disease was made, the multiple, clinical, and surgical management options were presented, and the case report was reported.  The authors concluded that MAS is a rare subtype of FD with endocrinopathy.  The FD of the orbital region can lead to optic nerve compression and possibly to visual loss.  They stated that there is no evidence to support the benefits of prophylactic surgery in children with normal visual fields and optic canal narrowing, shown by the CT or MRI, and there is no method to predict which child will stabilize or deteriorate the visual loss.  The cystic degenerations can lead to sudden visual loss and is the only possible indication for prophylactic surgery, but the risk of nerve damage should be considered and well-explained.  In all other cases of normal visual fields and CT/MRI optic canal narrowing, prophylactic surgery is not indicated, and follow-up should be done.  On the other hand, early decompression of symptomatic children is a great standard for a better chance of visual loss reverse..

In a retrospective, chart-review study, DeKlotz and colleagues (2017) evaluated visual outcomes and potential complications for optic nerve decompression using an endoscopic endonasal approach (EEA) for FD.  Patients with FD causing extrinsic compression of the canalicular segment of the optic nerve that underwent an endoscopic endonasal optic nerve decompression at the University of Pittsburgh Medical Center from 2010 to 2013 were included in this trial.  The primary outcome measure assessed was best-corrected visual acuity (BCVA) with secondary outcomes, including visual field testing, color vision, and complications associated with the intervention.  A total of 4 patients and 5 optic nerves were decompressed via an EEA.  All patients were symptomatic pre-operatively and had objective findings compatible with compressive optic neuropathy: decreased VA was noted pre-operatively in 3 patients while the remaining patient demonstrated an afferent pupillary defect; BCVA improved in all patients post-operatively.  No major complications were identified.  The authors concluded that EEA for optic nerve decompression appeared to be a safe and effective treatment for patients with compressive optic neuropathy secondary to FD.  Moreover, they stated that further studies are needed to identify selection criteria for an open versus an endoscopic approach.

Endoscopic Optic Nerve Decompression for the Treatment of Idiopathic Intracranial Hypertension

Tarrats and colleagues (2017) stated that the conventional treatment for IIH involves weight loss, steroids, diuretics, and/or serial lumbar punctures; however, if the symptoms persist or worsen, surgical intervention is recommended.  Surgical options include cerebro-spinal fluid (CSF) diversion procedures, such as ventriculo-peritoneal and lumbo-peritoneal shunts, and optic nerve decompression with nerve sheath fenestration.  The latter can be performed using an endoscopic approach, but the outcomes of this technique have not been firmly established.  This systematic review examined the outcomes of performing endoscopic optic nerve decompression (EOND) in patients with IIH; 6 studies were included for a total of 34 patients.  The patients presented with visual field disturbances (32 of 32 [100 %]), VA disruptions (33 of 34 [97.1 %]), papilledema (26 of 34 [76.5 %]), and persistent headache (30 of 33 [90.1 %]).  The mean duration of symptoms ranged from 7 to 32 months.  Overall, the patients showed post-EOND improvement in signs and symptoms associated with IIH, specifically visual field deficits (93.8 %), VA (85.3 %), papilledema (81.4 %), and headaches (81.8 %).  Interestingly, 11 cases showed post-operative improvement in their symptoms with bony decompression of the optic canal alone, without nerve sheath fenestration.  There were no major AEs or complications reported with this approach.  The authors concluded that EOND appeared to be a promising and safe surgical alternative for patients with IIH who failed to respond to medical treatment.  Moreover, they stated that further studies are needed to ascertain the clinical validity of this procedure.

Endoscopic Endonasal Optic Nerve Decompression for the Treatment of Optic Neuropathy Secondary to Fibrous Dysplasia

DeKlotz and colleagues (2017) evaluated visual outcomes and potential complications for optic nerve decompression using an endoscopic endonasal approach (EEA) for fibrous dysplasia.  These researchers carried out a retrospective chart review of patients with fibrous dysplasia causing extrinsic compression of the canalicular segment of the optic nerve that underwent an endoscopic endonasal optic nerve decompression from 2010 to 2013.  The primary outcome measure assessed was BCVA with secondary outcomes, including visual field testing, color vision, and complications associated with the intervention.  A total of 4 patients and 5 optic nerves were decompressed via an EEA.  All patients were symptomatic pre-operatively and had objective findings compatible with compressive optic neuropathy: decreased VA was noted pre-operatively in 3 patients while the remaining patient demonstrated an afferent pupillary defect; BCVA improved in all patients post-operatively.  No major complications were identified.  The authors concluded that fibrous dysplasia is a rare disease that can lead to compressive optic neuropathy and subsequent visual impairment.  Only patients with signs and/or symptoms of compressive optic neuropathy are candidates for surgery.  The EEA for optic nerve decompression appeared to be a safe and effective means of treating these patients.  It is unknown if endoscopic decompression can be successfully applied to most or all patients with this disease component or rather if only a select subgroup is likely to benefit and requires further study with longer follow-up.  They stated that while transcranial approaches are expected to continue to have a role in the management of these patients, the EEA shows promise and may become a preferred option for therapeutic intervention

The authors stated that this study had several drawbacks.  First, it was a small study population (n = 4).  Benign pathology of the canalicular segment of the optic nerve that is amenable to surgical decompression is rare.  The limited number of patients and interventions prevented making definitive statements about the overall efficacy and safety.  The current study only evaluated patients affected by fibrous dysplasia and whether this can be extrapolated to those with other fibro-osseous lesions is unknown.  The follow-up in the current study was limited (the mean follow-up was 14.8 months).  As demonstrated by 1 patient, there was the possibility for recurrent compressive optic neuropathy following endoscopic endonasal decompression.  Although there was no disease progression on imaging, his VA and color perception worsened on ophthalmologic testing and prompted a lateral decompression via craniotomy.  The prevalence of the need for additional interventions as well as timing following an endoscopic approach is unknown.  Additional work is needed in the future to fully define the role of endoscopic optic nerve decompression for fibrous dysplasia.  More concrete indications need to be determined to enable more widespread acceptance.  While randomized controlled trials (RCTs) are unrealistic given the rarity of these disorders, additional reporting of outcomes is needed to critically analyze and determine those likely to benefit from intervention.  While endoscopic optic nerve decompression appeared to have an emerging role in the management of these lesions, this did not mean that open cranial approach is now obsolete.  The potential benefits of improved visualization, preserved olfaction, more rapid recovery, lack of scarring, decreased operative stress, and lack of cerebral retraction would favor an endoscopic approach in some settings, though it is not universal.  Location of the pathology (medial versus lateral) is perhaps the most critical determinant of approach used as well as surgeon experience and comfort with a particular technique.  While the use of endoscopic endonasal decompression is expected to grow with further clarification of its indications, it is not expected to completely supplant traditional transcranial approaches.

Optic Nerve Decompression for Traumatic Optic Neuropathy and Non-Traumatic Compressive Optic Neuropathy

In a retrospective, case-series study, Pletcher and Metson (2007) determined the efficacy of EOND for the treatment of patients with non-traumatic optic neuropathy (NON).  A total of 10 EONDs were carried out on 7 patients with NON caused by various pathologic entities, including meningioma, lymphangioma, fibro-osseous lesions (fibrous dysplasia and osteoma), mucopyocele, and Graves orbitopathy.  Endoscopic instrumentation was used in a trans-nasal fashion to decompress the optic nerve.  Main outcomes measures were VA and complication rates.  Mean VA improved from 20/300 pre-operatively to 20/30 following surgery; VA improved by at least 2 lines on the Snellen chart following 7 of the 10 decompressions.  Median operative time was 133 mins, and median length of stay (LOS) was less than 24 hours.  Complications were limited to post-operative hyponatremia and corneal abrasions, both of which resolved with conservative therapy.  Mean follow-up time was 6.1 months.  The authors concluded that EOND appeared to be an effective treatment for restoring VA in select patients who presented with compressive optic neuropathy.

Kong and associates (2011) noted that compressive optic neuropathy is a rare condition that may be caused by trauma or non-traumatic events.  Endoscopic techniques have evolved to provide an easier surgical approach to decompression.  These investigators determined the endoscopic anatomy of the orbital apex and to identify the optimal targets for EOND.  They reported 5 patients with EOND: 2 with traumatic optic neuropathies, 2 with fibrous dysplasias, and 1 with chordoma.  For these lesions, the major treatment concern was removal of the bony structures around the optic nerve.  All compressive lesions were removed effectively via an endoscopic endonasal route.  Following EOND, 3 patients had markedly improved VA and fields of vision, 1 patient had improved fields of vision without change in VA, and 1 patient had improved VA alone.  There were no operative complications.  Adequate exposure of the intra-canalicular portion of the optic nerve was essential for effective decompression, and to achieve this, decompression of the roof as well as medial wall of the intra-canalicular portion was critical.  The authors concluded that EOND was a minimally invasive, safe, and efficient treatment for compressive optic neuropathy regardless of etiology.

Berhouma and colleagues (2014) stated that while several approaches have been described for optic nerve decompression, the endoscopic endonasal route is gaining favor because it provides excellent exposure of the optic canal and the orbital apex in a minimally invasive manner.  Very few studies have detailed the experience with non-traumatic optic nerve decompressions, whereas traumatic cases have been widely documented.  These researchers described their preliminary experience with EOND for NONs to determine the procedure's efficacy and delineate its potential indications and limits.  The medical reports of patients who had undergone endoscopic endonasal optic nerve and orbital apex decompression for NONs at the Lyon University Neurosurgical Hospital from January 2012 to March 2014 were reviewed.  For all cases, clinical and imaging data on the underlying pathology and the patient, including demographics, pre-operative and 6-month post-operative ophthalmological assessment results, symptom duration, operative details with video debriefing, as well as the immediate and delayed post-operative course, were collected from the medical records.  A total of 11 patients underwent EOND for NON in the multi-disciplinary skull base surgery unit of the Lyon University Neurosurgical Hospital during the 27-month study period.  The mean patient age was 53.4 years, and there was a clear female predominance (8 women and 3 men).  Among the underlying pathologies were 4 spheno-orbital meningiomas (36 %), 3 optic nerve meningiomas (27 %), and 1 each of trigeminal neuroma (9 %), orbital apex meningioma (9 %), ossifying fibroma (9 %), and inflammatory pseudotumor of the orbit (9 %); 54 % of the patients had improved VA at the 6-month follow-up.  Only 1 patient whose spheno-orbital meningioma had been treated at the optic nerve atrophy stage continued to worsen despite surgical decompression.  The 2 patients presenting with pre-operative papilledema totally recovered; 1 case of post-operative epistaxis was successfully treated using balloon inflation, and 1 case of air swelling of the orbit spontaneously resolved.  The authors concluded that EOND was a safe, effective, and minimally invasive technique affording the restoration of visual function in patients with non-traumatic compressive processes of the orbital apex and optic nerve.  The timing of decompression remains crucial, and patients should undergo such a procedure early in the disease course before optic atrophy.

In a retrospective study, Ren and associates (2015) described the preliminary experience with EOND for nontraumatic compressive optic neuropathies (NCONs).  These researchers an analyzed the clinical data of 10 patients (5 men and 5 women; mean age of 44.3 ± 5.1 years) who underwent EOND for visual loss (n = 5) or visual deterioration (n = 5) due to tumor compression in General Hospital of Armed Police Forces of China in the period from April 2013 to April 2014.  Pre-operative and 6-month-post-operative clinical and imaging data of these patients were reviewed.  Among the 5 patients who lost light perception (including 2 patients with bilateral optic nerve compression) before operation, 4 of them showed visual improvement to different degrees on the 7th day after operation (with improvement of bilateral VA).  The other 5 patients with visual impairment before operation recovered their VA to different extent after the operation.  All of the patients had no obvious post-operative complications.  The authors concluded that EOND was a safe, effective, and minimally invasive surgical technique affording recovery of visual function to NCON patients.

Liu and co-workers (2019) stated that many authors have reported on therapeutic strategies for traumatic optic neuropathy and their experience with endonasal EOND for traumatic optic neuropathy.  However, few have described the therapeutic strategies for NON and navigation-assisted EOND as a treatment for non-traumatic, compressive optic neuropathy.  In a retrospective study, these researchers examined the advantages in treating NON with the minimally invasive, image-guided, navigation-assisted, endonasal EOND.  This trial enrolled 20 patients (21 eyes) diagnosed with NON, undergoing an endonasal endoscopic approach to relieve space-occupying lesions and decompress the optic nerve under image-guided navigation.  This study described the authors’ research on the therapeutic strategies for NON patients, with special focus on the advantages of navigation-assisted, endonasal, EOND for the treatment of NON.  Medical photographs were used to estimate the status of the patients.  In 18 of the 20 cases, space-occupying lesions were completely resected.  In 2 cases, they were partially resected.  All 20 cases (21 eyes) underwent image-guided, navigation-assisted, endonasal EOND; VA improved in 20 eyes (95.2 %) and remained stable in 1 eye.  There were no intra-operative or post-operative complications.  The authors concluded that optic nerve decompression was the main treatment strategy for NON, to relieve space-occupying lesions and decompress the optic nerve, and to retain and/or improve VA.  Image-guided navigation could aid doctors pinpoint the optic nerve when facing anatomical deformation caused by a space-occupying lesion.  These investigators stated that navigation-assisted, endonasal EOND is a feasible, safe, practical, and minimally invasive approach.

Lin and associates (2021) stated that TON is a serious complication of cranio-facial trauma, which damages the optic nerve indirectly and results in dysfunction of VA.  The clinical intervention for TON patients includes optic canal decompression (with or without steroids), treatment with corticosteroids alone, or observation only.  Currently, there is controversy among clinicians as to which treatment is optimal.  An increasing number of retrospective studies have reported that patients could experience significant improvement in VA following optic canal decompression (OCD) surgery, especially endoscopic trans-nasal / trans-ethmosphenoid OCD (ETOCD), either with or without corticosteroids.  To-date, little consensus exists among neurosurgeons, ophthalmologists, and otolaryngologists concerning the optimum therapy for improved visual outcomes.  The authors concluded that it is clear that large, multi-center RCTs combined with a detailed epidemiological survey remains the best strategy for extending the understanding of TON and supplying a trustworthy strategic guide for therapy and for the standardization of surgical intervention.

Karimi and co-workers (2021) noted that TON is an uncommon vision-threatening disorder that can be caused by ocular or head trauma and is categorized into direct and indirect TON.  The overall incidence of TON is 0.7 % to 2.5 %, and indirect TON has a higher prevalence than direct TON.  Detection of an afferent pupillary defect in the presence of an intact globe in a patient with ocular or head trauma with decreased VA strongly suggests TON.  However, afferent pupillary defects may be difficult to detect in patients who have received narcotics that cause pupillary constriction and in those with bilateral TON.  Mechanical shearing of the optic nerve axons and contusion necrosis due to immediate ischemia from damage to the optic nerve micro-circulation and apoptosis of neurons is a probable mechanism.  The proper management of TON is controversial.  High-dose corticosteroid therapy and decompression of the optic nerve provide no additional benefit over observation alone.  Intravenous erythropoietin (EPO) may be a safe and efficient treatment for patients with TON.

Talwar and Ricci (2021) stated that traumatic orbital apex syndrome (TOAS) commonly occurs secondary to trauma and irreversible ischemic optic neuropathy occurs as early as 2 hours following injury.  Multiple therapeutic options have been described; however, there is a lack of consensus regarding the optimal treatment of these patients.  These researchers carried out a systematic review of the PubMed Database from 1970 to 2020, using the search terms "orbital apex", "syndrome" and "traumatic" with the Boolean operators "AND" or "OR".  Studies that did not describe TOAS, describe patient outcomes or treatments, and those without available full English text were excluded.  Patients were clustered and compared based on treatment received with the primary outcomes of improvement in vision or ophthalmoplegia.  A total of 347 studies were identified, of which 22 were included, representing 117 patients with TOAS.  A total of 89 (75.9 %) patients underwent decompressive surgery, 97 (82.6 %) received steroids, and 85 (72.2 %) received nerve growth factors.  Fewer than 20 % of patients were treated with antibiotics, diuretics, hormones, or hyperbaric oxygen.  Overall, 51.7 % of patients experienced improvement in vision and 85.2 % in ophthalmoplegia at 6 months.  Patients treated with surgical decompression (66.7 % versus 16.7 %, p < 0.01) or steroids (60.0 % versus 0 %; p < 0.01) were more likely to have improvement in vision than those without treatment.  Nerve growth factors did not improve vision; and ophthalmoplegia did not improve with any treatment.  The authors concluded that outcomes of TOAS tended to be poor, with overall low recovery of vision, although surgical decompression or steroid treatment suggested improved visual outcomes.  Moreover, these researchers stated that further standardized patient data are needed to elucidate the comparative effectiveness of these interventions.

Martinez-Perez et al (2021) stated that there exists a persisting controversy regarding the indications for optic nerve surgical decompression (ONSD) in the treatment of TON.  These researchers carried out a meta-analysis to aid in guiding therapeutic decisions and addressing gaps in knowledge.  They performed a search of PubMed and Medline electronic databases.  Primary endpoint was the improvement in the visual function with ONSD in comparison with the conservative management.  Secondary endpoint was visual function improvement when surgery was performed within the first 7 days.  A random effects model meta-analysis was conducted.  Data from each study were used to generate log odds ratio and 95 % CIs, to compare post-operative visual improvement.  A total of 9 studies met the inclusion criteria for analysis, comprising 766 patients.  Visual improvement occurred in 55 % (198/360) of patients treated with ONSD, and in 40 % (164/406) of those who underwent conservative treatment.  Forest plot revealed significant differences in the visual function improvement among these 2 groups, although further analysis revealed the studies were heterogeneous (log OR, 0.81; CI: 0.07 to 1.55; I2, 62.8 % p = 0.015).  The authors concluded that patients who underwent early surgery had better visual outcomes (log OR, 0.94; CI: 0.29 to 1.60; I2, 0 % p = 0.9); ONSD is an effective technique to improve the outcome in the visual function in patients with TON.  Moreover, these researchers stated that a lack of RCT as well as inherent surgical selection and publication bias limited direct comparison between surgical decompression and conservative management.  They stated that suitably designed prospective cohort studies may be useful in identifying patients more likely to receive benefit from ONSD.

On behalf of the American Academy of Ophthalmology (AAO), Wladis and colleagues (2021) examined the literature on the safety and effectiveness of medical and surgical interventions for indirect TON, defined as injury to the nerve that occurs distal to the optic nerve head.  These researchers carried out a literature search on October 22, 2019, and updated on April 8, 2020, in the PubMed database for English language original research that evaluated the effect of various interventions for indirect TON.  A total of 172 articles were identified; 41 met the inclusion criteria outlined for assessment and were selected for full-text review and abstraction.  On full-text review, a total of 32 studies met all of the study criteria and were included in the analysis.  No study met criteria for level I evidence; 7 studies (1 level II study and 6 level III studies) examined corticosteroid therapy that did not have uniformly better outcomes than observation; 20 studies (3 level II studies and 17 level III studies) examined optic canal decompression and the use of corticosteroids.  Although visual improvement was noted after decompression, studies that directly compared surgery with medical therapy did not report uniformly improved outcomes after decompression; 4 studies (1 level II study and 3 level III studies) evaluated the use of erythropoietin (EPO).  Although initial studies demonstrated benefit, a direct comparison of its use with observation and corticosteroids failed to confirm the usefulness of this medication; 1 study (level II) documented visual improvement with levodopa plus carbidopa.  Complication rates were variable with all of these interventions.  Pharmacologic interventions generally were associated with few complications, whereas optical canal decompression carried risks of serious side effects, including hemorrhages and CSF leakage.  The authors concluded that despite reports of visual improvement with corticosteroids, optic canal decompression, and medical therapy for indirect TON, the weight of published evidence does not demonstrate a consistent benefit for any of these interventions.  These investigators stated that no consensus exists from studies published to date on a preferred treatment for TON.  They noted that treatment strategies should be customized for each individual patient; more definitive treatment trials are needed to identify optimal treatment strategies for indirect TON.

Abdulmannan (2022) reported on a case of visual impairment following cranio-maxillofacial trauma.  The patient had sudden visual loss associated with fracture of the left orbital floor and medial and lateral wall of the left orbit and comminuted fracture of the left optic canal.  Access to the orbit was achieved through the endoscopic endonasal approach and the bone fragments, which had impinged on the optic nerve, were resected.  The patient had a total return of VA without surgical complications.  The author stated that there has been controversy regarding the surgical indication for a long time, and in early reports, surgery was undertaken only if there was an obvious fracture of the optic canal because craniotomy or trans-facial approaches had a high rate of complications.  The rationale for surgical decompression is that edema of the optic nerve or hemorrhage within the bony canal would impair the nerve's blood supply, resulting in ischemia and additional damage to the injured optic nerve.  The rationale behind optic nerve decompression is to partially remove the optic canal to decompress the nerve within the canal, limiting the detrimental effects of compression and restoring nerve function.  Decompression of the optic nerve lowers intra-canalicular pressure and enables the removal of any impinging bone fragments, allowing nerve function to be restored.  Systematic steroids have a similar effect, leading to ‘‘medical decompression’’.  There are numerous surgical approaches for optic nerve decompression that have been proposed (trans-frontal craniotomy, orbitotomy, and trans-ethmoidal and spheno-ethmoidal surgery).  The method chosen must be carefully evaluated in light of the location and extent of the orbital injury to select the most direct approach with the least morbidity.  A previous study reported the effectiveness of multiple procedures (endoscopic endonasal, transcranial, trans-ethmoidal, and endoscopic assisted medial trans-orbital) concerning TON surgery and concluded that visual improvement after surgical procedure ranged between 40 % to 75 % if it was performed in the early stage.  The endonasal approach is less invasive and shows excellent exposure to the optic canal and orbital apex than the classic transcranial approach.  Endoscopic optic nerve surgery is better tolerated by compromised patients, has a shorter operative time, preserves olfaction, avoids external scars, and reduces morbidity.  Patients of a younger age group have a better prognosis for VA outcomes.  Moreover, these researchers stated that future large-scale studies are needed to examine the effectiveness of this approach on patients with different types of trauma and different degree of severity.

Furthermore, an UpToDate review on “Optic neuropathies” (Osborne and Balcer, 2022) states that “Trauma -- Closed head injury may damage the optic nerve, usually affecting the intraorbital or intracanalicular segments.  The mechanism may be contusion or hemorrhage; rarely, the optic nerve is transected or avulsed.  In the latter case, vision does not improve.  Otherwise, the prognosis depends upon the extent of the injury; approximately half of patients recover.  Imaging studies and an ophthalmologic consult are indicated to evaluate for pathologies (optic nerve sheath hematoma, orbital hemorrhage) that require surgery.  Surgical decompression and high-dose corticosteroids are sometimes used but are not of proven benefit”.

Endoscopic Optic Nerve Decompression for Optic Neuropathy in Sino-Nasal Fibro-Osseous Tumors

Ryu and colleagues (2020) noted that sino-nasal fibro-osseous tumors involving the skull base sometimes result in the encasement of the optic canal and can cause the compressive optic neuropathy.  These researchers examined the optimal timing of EOND in cases with optic neuropathy caused by fibro-osseous tumors.  Medical records were reviewed retrospectively from July 2008 through November 2016.  Subjects who underwent surgery with EOND for optic neuropathy caused by fibro-osseous lesions were enrolled.  Pre- and post-operative ophthalmologic evaluation were analyzed, including BCVA, visual field testing, and color vision.  A total of 9 patients underwent EOND; 7 had fibrous dysplasia and 2 had juvenile ossifying fibroma.  Patients included 6 boys and 3 girls.  The average age was 15 years with a range of 8 to 17 years.  Symptom duration ranged from 2 months to 4 years.  The mean follow-up period was 28 months (range of 0.8 to 76.4 months).  There was no immediate deteriorated vision after EOND; 8 eyes (88.9 %) were improved and 1 eye (11.1 %) had only visual field improvement.  However, patients whose visual impairment was in the range of finger count and hand motion were not recovered beyond the quantitatively measurable level even after EOND.  The authors concluded that EOND in patients with optic neuropathy caused by a fibro-osseous tumor in the sino-nasal region was safe and worth trying to improve visual outcomes; early therapeutic EOND is recommended before the patient's visual function is decreased below quantitatively measurable vision.

Endoscopic Optic Nerve Decompression for Optic Nerve Sheath Meningiomas

Maza and colleagues (2019) stated that the management of optic nerve sheath meningiomas (ONSMs) remains controversial.  Surgical decompression through traditional resective techniques has been associated with significant morbidity.  While radiation therapy, the current modality of choice is not exempt of risks, trans-nasal EOND offers a direct route to the orbit, optic canal, and orbital apex, providing a minimally invasive alternative.  These researchers examined EOND as the initial management of symptomatic patients with primary ONSM.  Patients with ONSMs without a history of radiotherapy who underwent EOND were retrospectively reviewed. Postoperative imaging, duration of follow-up, and visual outcomes at the last ophthalmology visit were assessed. Results  Four women (age range 25-63 years) with primary ONSMs that underwent EOND were identified.  All patients displayed subjective and objective baseline signs of vision loss.  Additionally, baseline proptosis, diplopia, optic nerve atrophy, and ocular pain were identified.  In none of the cases, the optic nerve sheath was breached.  Following EOND, all patients deferred treatment with adjuvant radiotherapy.  At a mean post-operative follow-up of 14 months, all patients were clinically stable without evidence of disease progression on imaging or physical examination.  At last ophthalmologic evaluation, 3 out of 4 showed objective improvements from baseline VA and visual field (remaining patient had baseline optic nerve atrophy).  The authors concluded that these findings suggested that EOND could be a viable initial treatment modality of selected primary ONSM cases.  Moreover, these researchers stated that further studies are needed to determine long-term efficacy of EOND and its role in a step-wise progression of management, preceding radiotherapy.

Endoscopic Trans-Nasal Optic Nerve Decompression Prior to Radiosurgery for the Treatment of Parasellar Meningiomas

Matousek et al (2022) noted that the clinical management of parasellar meningiomas (PM) is challenging due to their intimate association with critical neurovascular structures.  Consensus regarding the recommended treatment protocol is lacking.  In a retrospective study, these researchers examined patients' visual outcomes following endoscopic trans-nasal optic nerve decompression (ETOND) and examined the possibility of reducing the rate of complications associated with stereotactic radiosurgery (SRS).  This trial was carried out on all patients who underwent ETOND for PM between 2013 and 2020.  The study comprised 12 patients (7 women and 5 men, aged 36 to 75 years; mean of 55.2 years; median of 57.6 years) in which 14 optic nerve decompression procedures were performed.  Patients were followed-up for 6 to 86 months (mean of 29.3 months; median of 25 months).  There were 5 cases of spheno-orbital meningioma, 4 cases of cavernous sinus meningioma, and 1 case each of petro-clival meningioma, optic nerve sheath meningioma, and planum sphenoidale/tuberculum sellae meningioma.  Visual outcome was evaluated; and any post-operative complications noted.  Improvements in VA were noted in 10 of 14 eyes (71.4 %) 3 to 6 months post-operation; and VA remained stable in the remaining 4 eyes.  No deterioration of VA was noted during the follow-up period.  In total, 9 of the 12 patients underwent SRS.  No tumor growth was determined, while reduction in tumor volume was noted in 5 patients following SRS.  No complications associated with SRS or the surgical procedure were noted.  The authors concluded that ETOND appeared to be a promising technique for increasing rates of improved visual function, while reducing the risk of post SRS-related complications.  In combination with subsequent SRS, it is an ideal treatment modality in the management of parasellar meningiomas.   Moreover, these researchers stated a larger, prospective, multi-center study with long-term patient monitoring is needed to confirm these preliminary findings.

Endoscopic Trans-sphenoidal Endonasal Optic Nerve Decompression with Durotomy

Srivastava and colleagues (2020) stated that progressive vision loss is a dismal sequelae of idiopathic intracranial hypertension (IIH) and secondary intracranial hypertension with cerebro-venous sinus thrombosis (CVST).  The initial management revolves around weight loss, acetazolamide, steroids, and diuretics.  A subset of unfortunate patients, refractory to medical therapy, need surgical intervention in the form of CSF diversion or optic nerve decompression (OND).  The endoscopic endonasal optic nerve decompression with durotomy (ONDd) is an emerging alternative with encouraging early results.  Ina retrospective, non-comparative review, these researchers presented their experience of ONDd by endoscopic endonasal corridor, highlighting the technical nuances of procedure and discussed the indications of the same in the era of advanced technology.  This review included medical records of all the patients of IIH (ICHD-III criteria) with severe vision loss, refractory to medical treatment, and with established objective evidence of papilledema.  All the patients were operated in the authors’ department by endoscopic endonasal sheath fenestration.  A total of 9 patients (M:F 3:6) underwent endoscopic endonasal optic nerve decompression (2016 to 2019) approach for medically refractive IIH (n = 6) and CVST (n = 3).  The mean age of population was 21.44 ± 5.14 years; 6 patients had improvement in headache and 6 had improvement in visual acuity (VA).  The VA deteriorated in 2 patients (n = 1 IIH and n = 1 CVST with dural arterio-venous fistula [AVF]); 1 patient needed post-operative lumbar drain for CSF leak, while none had meningitis.  The authors concluded that endoscopic optic nerve sheath fenestration was a minimally invasive and effective alternative with promising outcome in the management of medical refractory IIH or CVST.

The authors stated that this study had a small sample size (n = 9), but the rarity of disease precluded a large size surgical data.  With only 9 patients, this series was largest of its kind.  Selection and referral bias may be an additional drawback; however, these researchers just wanted to highlight feasibility and credibility of the procedure, not exactly comparing it with any established standard procedure.  The approach was cost-effective with unsubstantial learning curve.

An accompanying editorial (Thakar A, Aggarwal A, 2020) noted that one of the 9 patients developed a postoperative CSF leak necessitating a temporary lumbar drain. The editorialist stated that the study also noted in passing that all patients had minor CSF leaks and 'postnasal drip' for the first 2 to 3 postoperative days. The editorialist noted that spontaneous and recurrent CSF leaks are well documented as complications of IIH, and creating a deliberate CSF fistula in the sphenoid is likely to further augment such risks.

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References