Woman presents with vision changes, orbital mass
Click Here to Manage Email Alerts
A 43-year-old stay-at-home mom was referred to the Tufts New England Eye Center for a newly identified orbital mass and vision changes in her right eye.
Her symptoms began as mild blurry vision 3 months before presentation. Her entire visual field at near and at distance was affected, but she could still read and drive a car. She denied progression of the visual changes and had no double vision. Her optometrist of many years had retired. Upon seeing a new optometrist for the first time, she was found to have elevated right eye pressure and an abnormal right optic disc. She was then referred to a local ophthalmologist who started Combigan (brimonidine tartrate 0.2%/timolol maleate 0.5% ophthalmic solution, Allergan), Lumigan (bimatoprost ophthalmic solution 0.01%, Allergan) and dorzolamide in both eyes for IOPs of 35 mm Hg and 22 mm Hg in the right and left eyes, respectively. He also saw right optic nerve edema and ordered a CT scan, which showed an orbital tumor that was confirmed on MRI.
The patient had Graves’ disease for 17 years that was well controlled on levothyroxine as well as a remote history of migraines. There was no history of eye trauma or surgery, and she follows yearly with optometry for reading glasses. Review of systems was notable for mild headaches that occur once or twice weekly and were unchanged in character and present for many years. She was allergic to sulfa drugs and did not drink alcohol or use illicit drugs or tobacco products.
Examination and testing
The patient’s visual acuity was 20/30 in the right eye and 20/25 in the left eye. Pinhole improved vision in the left eye to 20/20 but did not improve acuity in the right eye. Pupils were equal in size, but there was a relative afferent pupillary defect in the right eye. IOPs were 28 mm Hg in the right eye and 16 mm Hg in the left eye in primary gaze. The pressure in the right eye increased to 40 mm Hg on right gaze and 30 mm Hg on left gaze. There was limited adduction and elevation of the right eye and full extraocular movements of the left eye. She identified 10/14 HRR color plates with the right eye and saw all color plates with the left eye. The right eye was prominent, and exophthalmometry measurements were 20 mm on the right and 17 mm on the left. The external and anterior segment exams were unremarkable, and there was no lid retraction or lag. Fundus exam demonstrated moderate pallor and mild edema of the right optic nerve, and there was mild tortuosity of the veins (Figure 1).
Source: Gavin Gorrell, MD, and Thomas R. Hedges III, MD
On OCT, there was elevation of the right optic nerve and diffuse ganglion cell loss, with the possible combination of edema and atrophy resulting in an average retinal nerve fiber layer (RNFL) in the normal range (Figure 2). The right visual field was constricted, and the left was normal (Figure 3). MRI of the brain and orbits demonstrated a right orbital mass surrounding the optic nerve and indenting the posterior globe. There was mild enlargement of the extraocular muscles bilaterally (Figure 4).
Acetazolamide was started for elevated IOP, and neurosurgery was consulted to review the images.
What is your diagnosis?
See answer below.
Optic nerve mass
The differential diagnosis of an optic nerve mass includes glioma, optic nerve sheath meningiomas, optic neuritis (including MOG antibody disease), metastasis to the orbit, orbital lymphoma and orbital sarcoidosis. In this 43-year-old woman with slow, painless visual changes, optic atrophy and perineural tumor with clear optic nerve delineation, the most likely diagnosis is optic nerve sheath meningioma. The neurosurgery team felt that the appearance of the tumor was classic for optic nerve sheath meningioma and recommended radiation treatment over biopsy or surgical intervention.
Discussion
Optic nerve sheath meningiomas (ONSMs) are the second most common optic nerve tumor after optic nerve gliomas and are the most common in adults. However, they represent only 1% to 2% of all meningiomas. Most meningiomas of the orbit are extensions from intracranial sites. A true optic nerve sheath meningioma is a proliferation of meningothelial cells within the intraorbital optic nerve sheath. Ninety-five percent of ONSMs are unilateral and, like other meningiomas, show a female predominance. The average age at presentation of unilateral ONSM is 40.8 years; bilateral cases often present in the first decade of life and are associated with neurofibromatosis type 2.
The pathognomonic triad of ONSM includes painless progressive vision loss, optic atrophy and optociliary shunt vessels, although it is rare for a patient to have all three. ONSMs most commonly present as insidious blurred vision or decreased color vision. Nearly all patients will have evidence of optic nerve dysfunction upon presentation, including loss of visual acuity, relative afferent pupillary defect, reduced color vision and/or visual field loss, typically constricted peripheral fields. Transient visual obscurations that are spontaneous or gaze evoked may also be present. Mild proptosis is present in 60% of patients, and extraocular motility defects from mechanical restriction can be seen.
The optic nerve may be normal in early presentations but may develop edema from tumor compression of the intraorbital nerve followed by atrophy. Optociliary shunt vessels are preexisting collaterals between the retinal and choroidal venous system that dilate in response to chronic obstruction of central retinal vein outflow. These shunt vessels are present in 30% of ONSMs but are nonspecific and can be seen in other compressive optic nerve conditions, especially papilledema.
Diagnosis is best made on MRI of the brain and orbits with contrast enhancement. Before modern MRI, diagnosis was made by biopsy, which carried a high risk for morbidity and vision loss, and for this reason, biopsy is rarely needed except in atypical cases. Meningiomas typically have homogenous enhancement, which helps in differentiation of the non-enhancing optic nerve tissue. ONSMs often expand circumferentially around the optic nerve in a tubular pattern, appearing as a “tram track sign” on axial view and a “doughnut sign” on coronal sequences. Less common ONSM growth patterns are globular and fusiform, but in all cases, the tumor grows outside of the optic nerve. ONSMs can be distinguished from optic nerve gliomas, which show intrinsic enlargement of the optic nerve on imaging.
The mortality of ONSM is effectively nil, so treatments for this condition are based on patient age, comorbidities and symptoms at presentation. Although unpredictable in rate of progression, ONSMs are often slow growing. Therefore, observation with close follow-up and serial MRI scans is an option for patients with negligible visual disturbance. Treatment is typically recommended when vision deteriorates below 20/40 or the visual field constricts. Fractionated stereotactic radiation is considered the preferred intervention for ONSM, with some series demonstrating 88% to 95% stability or improvement in vision and arrest of growth on subsequent MRIs more than 10 years after treatment. Potential ocular side effects of radiation include radiation-induced retinopathy and optic neuropathy, iridocyclitis and cataract formation. Patients may also develop endocrinologic changes associated with pituitary insufficiency. Surgery is typically a blinding procedure, as the ONSM and the optic nerve share the same blood supply, and there is often local recurrence. Surgery may be indicated in aggressive tumors with intracranial extension to prevent spread to the contralateral eye or in cases of disfiguring proptosis.
Case continued
Our patient’s elevated IOP is not typical of ONSM and has not been reported in the literature. However, this is a well-documented finding in other orbital tumors. We suspect this may be related to concurrent thyroid eye disease, which caused restriction of eye movement and also applied posterior pressure to the eye. At her follow-up visit, the IOP had decreased to 22 mm Hg in the right eye and 16 mm Hg in the left eye after the addition of acetazolamide. Radiation oncology recommended fractionated, conformal image-guided radiotherapy 5 days per week for 28 sessions.
- References:
- Douglas VP, et al. Curr Opin Ophthalmol. 2020;doi:10.1097/ICU.0000000000000700.
- Narayan S, et al. Int J Radiat Oncol Biol Phys. 2003;doi:10.1016/s0360-3016(03)00005-1.
- Nassr MA, et al. Surv Ophthalmol. 2009;doi:10.1016/j.survophthal.2009.02.023.
- Optic nerve sheath meningioma. eyewiki.aao.org/Optic_Nerve_Sheath_Meningioma. Updated April 27, 2020.
- Optic nerve sheath meningioma and intracranial meningioma. In: BCSC Neuro-Ophthalmology. American Academy of Ophthalmology; 2019:126-131.
- Pandit R, et al. Br J Ophthalmol. 2019;doi:10.1136/bjophthalmol-2018-313135.
- Shapey J, et al. J Clin Neurosci. 2013;doi:10.1016/j.jocn.2013.03.008.
- For more information:
- Gavin Gorrell, MD, and Thomas R. Hedges III, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Christine Benador-Shen, MD, and Malgorzata Dymerska Peterson, MD. They can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.