Optic-nerve Sheath Meningiomas - Clinical-features and Functional Prognosis

Seventeen cases of optic nerve sheath meningiomas were reviewed, in order to identify their clinical presentation, CT and MRI features, and to evaluate their visual prognosis in untreated cases and after surgery. The most common clinical features were represented by optic disk pallor and/or edema (16 cases), unilaterally reduced visual acuity (14 cases), afferent pupillary defect (12 cases), visual field alterations (nine cases out of 12), proptosis (12 cases), motility disturbances (eight cases), amaurosis fugax (five cases). On CT and MRI, eight tumors appeared fusiform, four excrescent, four tubular, one massive. The optic nerve could be recognized within the tumor in nine cases out of 16 on CT, and in eight out of nine on MRI. Contrast enhancement was observed in most cases. On T-2-weighted MRI, meningiomas proved to be hyperintense in four cases and isointense to fat in the remaining five. A histological diagnosis was obtained in eight cases: seven belonged to the meningotheliomatous type; the remaining to a transitional type. The visual prognosis in untreated patients was extremely variable and unpredictable on the basis of clinical, radiological or epidemiological factors. Of the six cases who had undergone neurosurgery, none experienced a visual improvement; two cases suffered a sudden visual deterioration. Optic nerve sheath meningiomas should be suspected when unilateral visual impairment is associated with optic disk alterations and proptosis. Contrast-CT is the first advised diagnostic step, followed by contrast-MRI if the diagnosis should be unclear.