Optic Nerve Sheath Meningioma

    • Benign tumor growing from the meninges of the orbital portion of the optic nerve
    • Compresses the intraorbital and/or intracanalicular optic nerve to cause painless progressive monocular visual loss
    • Affects mostly young and middle-aged women
    • Biopsy may worsen vision permanently
    • Radiation therapy may prevent visual decline
    • Core clinical features
      • Slowly progressive painless monocular visual loss
      • Minimal if any proptosis
      • Afferent pupil defect on the affected side
      • Nerve fiber bundle defect and sometimes reduced visual acuity
      • Optic disc appears normal, elevated (sometimes with shunt vessels), or pale
    • Possible accompanying clinical features
      • Increased resistance to retropulsion of the affected eye
    • Imaging features
      • MRI shows a linear or lobular mass around the orbital optic nerve
    • Trap: this tumor may go undetected on imaging protocols that do not include contrast and do not adequately visualize the orbit
    • Trap: distinguishing chronic dural inflammation and orbital lymphoma from optic nerve sheath meningioma is difficult by MRI alone
    • Atypical optic neuritis
    • Pilocytic astrocytoma (optic glioma)
    • Infiltrative (neoplastic) optic neuropathy
    • Dural inflammation
    • Lymphoma
    • Varix
    • Cavernoma
    • Order orbit-based MRI
    • Base your diagnosis presumptively on imaging, as biopsy is too destructive of vision
    • Tip: CT is useful to show calcium in the lesion, which would be more typical of meningioma than of dural inflammation or lymphoma
    • Tip: an empirical trial of prednisone 1mg/kg/day for 14 days is also useful because meningioma is hard to distinguish from dural inflammation or lymphoma; visual improvement suggests dural inflammation or lymphoma rather than meningioma
    • If vision does not improve with prednisone treatment, recommend radiation therapy if
      • Vision is still reasonably intact in the affected eye
      • Vision is worsening in the affected eye
      • Unaffected eye has poor vision
    • Visual loss spontaneously worsens in 75% and remains stable in 25%
    • Tip: further intracranial tumor growth that compromises the fellow optic nerve or the optic chiasm is low and should not be used to justify radiation therapy
    • Radiation therapy improves vision in 10%, stabilizes vision in 80%, but does not prevent continued vision loss in 10%
    • Late visual loss or other complications of radiation therapy are rare if proper technique is applied
    • Trap: inexpert radiation therapy may cause a severely dry eye and loss of vision from infarction of the optic nerve and bleeding in the retina, often months to years later

    Optic Nerve And Chiasm Disorders

    Drusen Optic Neuropathy Colobomatous Optic Neuropathy Optic Pit Neuropathy Morning Glory Optic Neuropathy Hypoplastic Optic Neuropathy Typical Optic Neuritis Atypical Optic Neuritis Papillitis (Neuroretinitis) Non-arteritic Ischemic Optic Neuropathy Arteritic Ischemic Optic Neuropathy Posterior Ischemic Optic Neuropathy Hypotensive Ischemic Optic Neuropathy Radiation-induced Optic Neuropathy Diabetic Papillopathy Hypertensive Optic Disc Edema Papilledema Idiopathic Intracranial Hypertension (Pseudotumor Cerebri) Compressive Optic Neuropathy: Overview Optic Neuropathy of Graves Disease Optic Nerve Sheath Meningioma Sphenoid Meningioma Craniopharyngioma Pituitary Adenoma Pilocytic Astrocytoma (Optic Glioma) Carotid Aneurysm Suprasellar Germinoma Infiltrative (Neoplastic) Optic Neuropathy Paraneoplastic Optic Neuropathy Traumatic Optic Neuropathy Toxic Optic Neuropathy Nutritional Deficiency Optic Neuropathy Dominantly-Inherited Optic Neuropathy Leber Hereditary Optic Neuropathy Primary Open Angle Glaucoma