Optic Nerve Sheath Meningocele With Optic Disc Pit: A Rare Finding

Abstract

A 13-year-old girl presented with complaints of painless, progressive protrusion of her left eye for last 2 years with mild visual blurring. She had 4 mm proptosis in her left eye with relative afferent pupillary defect. Visual acuity in the right eye was 20/20 and in the left eye was 20/25 on Snellens acuity testing. MRI revealed a well-circumscribed, cerebrospinal fluid signal intensity cystic lesion medial to the optic nerve (Figs. 1 and 2). Optic nerve sheath meningocele is a primary enlargement of the optic nerve sheath. Optic nerve sheath meningocele can present with progressive hyperopia and choroidal folds in middle-aged males. Proposed theories of pathophysiology of optic nerve sheath meningocele are either congenital narrowing of the optic/cranio-orbital junction causing cerebrospinal fluid accumulation in the perioptic subarachnoid space or a difference in osmotic gradient between the cerebral and perioptic subarachnoid space. The radiologic examination of choice is MRI with fat suppression which shows enlargement of the optic nerve sheath isointense with cerebrospinal fluid. There has been no consensus about management for these patients. Patients with progressive visual loss have been treated by optic nerve sheath fenestration leading to halting of the progression. Supplementary management with acetazolamide, especially in patients with associated increased intracranial pressure, is advisable. Our patient has no such complaints and is under periodic review.FIG. 1.: Clinical and investigational pictures of patient of optic nerve sheath meningocele with optic disc pit. Upper right Fundus photograph of left eye showing the posterior pole with a nasal optic disc pit with RNFL edema and radiating choroidal folds. Left Humphrey Visual Field of the left eye. Lower right Worm’s view external photograph of the patient.FIG. 2.: Clinical and investigational pictures of patient of optic nerve sheath meningocele with optic disc pit. A, T1-weighted image of axial MRI. B: T2-weighted fat-suppressed image showing intraconal cystic lesion medial to the optic nerve with similar signal intensity as cerebrospinal fluid. C, T2-weighted sagittal MRI.