Optic Nerve Sheath Meningiomas

Robert Egan MD

Casey Eye Institute

Department of Ophthalmology, Neurology, and Neurosurgery

Oregon Health & Science University

Portland, Oregon

November 4th, 2006

Optic Nerve Sheath Meningiomas

• Optic nerve sheath meningiomas (ONSM) are separated into two types: primary and secondary

• The primary variety arises from the cap cells of the intraorbital or intracanalicular optic nerve sheath while the secondary form arises intracranially in the region of the sphenoid wing, tuberculum sella, or olfactory groove

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Secondary ONSM• Painless and slowly progressive vision loss with or without diplopia• Sphenoid wing meningiomas may be associated with significant

disfiguring proptosis• Optociliary shunt veins are not associated with this disorder, but

optic atrophy or papilledema may be present if direct tumor compression of the optic nerve or increased intracranial pressure has resulted

• Neuroimaging is the mainstay for diagnosis in a typical case• Treatment consists of surgical resection with or without radiation

therapy; it is reasonable to follow these patients clinically until symptoms worsen

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Primary ONSM• The average age of onset of symptoms from these tumors is in the

5th decade of life although they may be found at any age • Some patients may even present in their 7th decade of life • ONSM account for less than 1% of all meningiomas and for only 3

to 14% of orbital tumors • Men are affected much less frequently than women and prevalence

rates are recorded from 7.1% to 37.5%• These tumors may occur more frequently in the setting of

neurofibromatosis type 2 and may be bilateral • Bilateral tumors, albeit rare, tend to present at an earlier age

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Primary ONSM• Most patients with ONSM complain of reduced or blurred vision in

one eye • There often is little if any proptosis • Visual acuity at presentation may be 20/40 or better in half of

patients and less than 25% are count fingers acuity or worse • Roughly 50% present with disc edema; the other half with pallor • Visual fields typically show central and paracentral scotomata as

well as altitudinal defects and these progress over time • Despite the typical progression of reduction in visual function,

some patients maintain stable acuity for years or actually improve and this may occur in up to 30%

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Primary ONSM

• A few patients will show choroidal folds due to compression behind the globe

• Optociliary shunt vein collaterals in the presence of vision loss and optic disc pallor should suggest the diagnosis of an ONSM

• However, shunt veins are uncommon at presentation, but become apparent in over 1/3 of patients over a 6 year period

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Primary ONSM• ONSMs are most easily visualized by CT or MRI as a fusiform

enlargement of the optic nerve/sheath complex • There may also be flattening of the posterior globe due to tumor

encroachment and the optic canal may be enlarged • ONSMs tend to calcify over time; on CT, there may be

circumferential calcification and bright signal or enhancement that resembles railroad tracks on axial sections and a double ring on coronal sections

• ONSMs are hypointense on both T1‑ and T2‑weighted MR images and typically enhance well after administration of gadolinium

• Rarely, the ONSM may appear cystic

Primary ONSM• Care should be taken to make the presumptive

diagnosis of an ONSM in a patient with a history of breast carcinoma

• Occasionally, metastases from breast may mimic an ONSM and be misdiagnosed radiologically

• Therefore, a biopsy should be undertaken in the patient with an “ONSM” and breast CA

• Arachnoid cysts of the optic nerve and sarcoidosis may rarely mimic an ONSM

Primary ONSM• Average age of onset in the 5th decade of life• Associated with painless and slowly progressive vision

loss• Minimal proptosis, if any• Optociliary shunt veins may be present on the optic disc• Neuroimaging is the mainstay for diagnosis in a typical

case• Radiation is treatment of choice in an eye that is having

documented progressive vision loss

Primary ONSM• Left alone, unilateral ONSMs slowly but inexorably

progress to produce blindness of the involved eye • However, this is not always the case • Some patients maintain stable vision for years or even

enjoy mild improvement • Intraorbital and intracanalicular meningiomas extend

intracranially only rarely and are not associated with any mortality

• In contrast, tumors that begin intracranially often extend to involve the chiasm and other structures adjacent to the optic nerve and may lead to blindness of the other eye

Primary ONSM

• Surgical removal is not indicated due to the high likelihood of inducing blindness

• This is caused by the unavoidable dissection of the pial vascular supply of the optic nerve

• This option may be considered in an eye that is already blind

Primary ONSM• Recently, several series have been published documenting

treatment outcomes with 3 dimensional conformal radiation therapy (3D-CRT) or stereotactic fractionated radiotherapy

• In total, these reports indicate that some patients will have improvements in acuity, but more commonly enjoy improvement in visual field

• A greater number of patients develop stability in their visual acuity and visual fields while only a small number worsen

• Cilioretinal shunt veins may regress as the tumor shrinks

Primary ONSM• Risks of radiation therapy are not well understood at this

time as only a few small sized treatment studies have been published with limited follow up

• There are several reports of radiation retinopathy as well as iritis, dry eye, or orbital pain

• Since these tumors are uncommon, it remains likely that the true prevalence of complications will only be inferred through case reports and other small series

• Complication rates may decrease with greater application of 3D conformal techniques

Primary ONSM• Since some patients may not progress for years, close

follow up is recommended • The routine application of radiation therapy may

unnecessarily expose some patients to complications and should be reserved for those patients whose visual function declines under close observation

• Therefore, since the long term risks of radiation treatment are still not fully known and these tumors only cause blindness without other morbidity or mortality, observation should remain part of the treatment armamentarium and discussed with each patient

Susac Syndrome