Optic Nerve Sheath Meningiomas

1
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

2
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

3
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

4
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

5
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

6
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

7
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

8
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

9
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

10
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

11
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

12
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

13
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

14
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

15
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

16
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

17
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

18
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

19
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

20
Susac Syndrome