Primary melanoma of the sphenoid sinus presenting with a third cranial nerve palsy

An 83-year-old woman presented with right trigeminal paresthesias, upper lid ptosis, and diplopia and was found to have a right third cranial nerve palsy. MRI disclosed a right sphenocavernous mass with speckled high signal on pre-contrast T1 and correspondingly low signal on T2. Endoscopic sphenoidotomy revealed malignant melanoma. The patient underwent radiation therapy with complete and protracted resolution of the palsy. An extensive evaluation for a primary source was negative. The combination of high T1 signal and low T2 signal in a mass should suggest melanin. An exceedingly rare condition, this is the first English report of its presentation with a third cranial nerve palsy.