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