A 44-year-old woman presented for a LASIK consultation but was found to have unilateral optic disc edema in her left eye. Further workup with MRI revealed enhancement of the left optic nerve consistent with an optic nerve sheath meningioma. These types of tumors typically involve the orbital portion of the optic nerve and enhance with contrast in a characteristic "tram track" pattern on imaging. As the patient's examination and vision were stable, she was recommended for observation with serial exams and imaging to monitor for signs of progression.

1. Case
Presentation
A middle-aged woman seeks a
LASIK consult, but unilateral disc
edema leads the examination on a
new course.

2. PRESENTATION:
 A 44-year-old woman with a medical
history of depression and ocular
history of mild myopia presented for
LASIK evaluation.
 Her best-corrected visual acuity was
20/20 in both eyes, but examination
revealed a swollen optic disc in the
left eye.
 LASIK surgery was declined and she
was referred for evaluation of the
unilateral optic nerve head swelling.
She recalled minor head trauma three
months earlier.
 Systemic review of symptoms was
negative except for a subjective
sensation of tingling of left side of
her head and earlobe. She denied
pain and decreased vision.

3. Medical History
 She denied any history of
vision loss, eye pain or
systemic neurologic symptoms
(weakness, numbness,
paralysis).
 She smoked one pack of
cigarettes per day for 30 years,
described minor social alcohol
use and no other drug use.
 Medications included only
Escitalopram (Lexapro) 10 mg
daily.
 She had no family history of
systemic problems.

4. On examination…
• Examination showed a best corrected
visual acuity of 20/20 in each eye.
• Pupil examination noted 1 mm of
anisocoria that was the same in light
and dark with no afferent pupillary
defect.
• Applanation intraocular pressures
were 18 mmHg and 15 mmHg.
• She had full ocular motility, full
confrontational fields and color plate
testing was full.

5. On examination…
• Hertel measurements were 15
mm OD and 16 mm OS with a
base of 105 mm.
• She denied red desaturation.
• Anterior segment examination
revealed normal findings

6. The right eye showed 1+
hyperemia without disc elevation.

7. The left eye was noted to have 3+ disc
elevation and 3+ hyperemia without
visible drusen.

10. What is your
differential
diagnosis?
What further
workup would you
pursue?

11. A broad differential diagnosis can be generated
for unilateral optic disc edema.
 Traumatic
 Demyelinating/autoimmune (multiple
sclerosis, neuromyelitis optica, lupus
erythematosis, thyroid eye disease)
 Infectious conditions (tuberculosis,
lyme disease, syphilis, herpetic,
bartonella)
 Infiltrative/inflammatory (neoplasm,
sarcoidosis, drusen)
 Congestive (orbital
pseudotumor/cellulitis)
 Vascular (diabetic papillopathy, giant
cell arteritis, nonarteritic anterior
ischemic optic neuropathy).

12. Workup
B-scan ultrasonography
revealed no optic disc
drusen.
Humphrey visual field
testing showed
peripheral relative and
absolute scotomas

16. Workup
Initial magnetic resonance imaging
of the brain demonstrated a left
optic nerve with diffusely increased
diameter, with a mildly infiltrative
appearance of the intraconal and
retro-orbital fat without extraocular
muscle enlargement. Mild proptosis
was also noted.
After gadolinium, there was
significant enhancement of the left
optic nerve as seen above. The
remainder of the scan including
cavernous sinus and pituitary was
unremarkable.

17. Diagnosis
• Based on her clinical findings,
her differential diagnosis was
narrowed to:
1. Optic nerve meningioma
2. Optic nerve drusen
3. Resolving optic neuritis
4. Optic nerve glioma.

18. ONSM

19. ONSM
 Her imaging was thought to be most
consistent with an optic nerve sheath
meningioma involving the orbital
portion without extension into the
canal.
 She was seen again six weeks after
initial evaluation and the findings were
unchanged.
 Given the stability of her examination,
visual fields, her good vision and lack
of color abnormalities, it was
recommended that she have no active
treatment.
 She was referred for consultation with
neurosurgery, and advised to return if
she noticed any change in vision.
 Serial MRI images have shown
stability of the optic nerve
meningioma and the patient has
remained asymptomatic.

20. Discussion
 Optic nerve sheath meningiomas are
benign neoplasms of the optic nerve
sheath.
 Although rare, ONSM is the second-
most common primary optic nerve
tumor and represents 1-2% of all
meningioma
 Show positive immunoreactivity for
vimentin and may contain psammoma
bodies.
 Malignant transformation is
exceedingly rare.
 For unknown reasons, there is a
higher incidence of optic nerve sheath
meningiomas in middle-aged women.
 There is also an association with
neurofibromatosis type 2.

21. A classic triad of an ONSM:
Progressive visual loss
Optic nerve atrophy
Presence of optociliary collateral vessels

23. Discussion
 The tumor typically tracks along the
optic nerve sheath and can grow to
surround and compress the optic
nerve, central retinal artery or the
central retinal vein.
 Vision loss is usually caused by a
compressive optic neuropathy, but
patients may live without symptoms
for decades.
 The mass can also grow back towards
the chiasm and cause contralateral
field deficits.
 Patients may demonstrate the classic,
pathognomonic clinical triad for
ONSM, consisting of painless, slowly
progressive vision loss, optic atrophy,
and optociliary shunt vessels.
 Axial proptosis, optic disc edema,
color vision abnormalities and
extraocular muscle movement
abnormalities may also be noted.

24. The tram-track sign is extremely useful in
the differentiation between optic nerve
sheath meningiomas and optic nerve
gliomas.
The optic nerve may be thickened and
infiltrated by the glioma, but its sheath
generally does not demonstrate contrast
uptake.
The tram-track pattern, in spite of being a
characteristic sign, is not specific of optic
nerve sheath meningiomas, and may
occur in orbit pseudotumors, perioptic
neuritis, sarcoidosis, leukemia and
lymphoma

25. Discussion
 MRI will demonstrate diffuse, tubular
thickening of the optic nerve sheath
encasing the optic nerve, often
producing a characteristic "tram
track" sign on axial cuts or a
"doughnut" sign on coronal cuts. The
tumor enhances with contrast
infusion.
 In asymptomatic patients, observation
with exams every six to 12 months
including vision, pupils, color vision,
visual fields as well as periodic MRI
imaging is indicated.
 Many patients do have progressive
visual loss over time, but there are
currently no tests available that can
predict the aggressiveness of these
benign neoplasms.
 If there is progression of a patient’s
symptoms, the optic nerve can be
approached with radiotherapy or
gamma knife surgery.