Delayed diagnosis of a right third nerve schwannoma. A, An 11-year-old patient was noted to have a right third nerve palsy that began at age 5 years and became complete by age 7 years. B, Initial study results were negative, but fine cuts through the cavernous sinus demonstrated asymmetry, with a slight nodule in the superior portion of the cavernous sinus on the right. C, This area became bright with administration of gadolinium contrast, which indicated the presence of a right third nerve schwannoma (arrow).