A rare, mostly benign, primary tumor of the meninges (arachnoid cap cells), usually located in the supratentorial compartment, commonly appearing in the sixth and seventh decade of life, clinically silent in most cases or causing hyperostosis close to the tumor and resulting in focal bulging and localized pain in less than 10% of cases. Additional features may include headache, seizures, gradual personality changes (apathy and dementia), anosmia, impaired vision, exophthalmos, hearing loss, ataxia, dysmetria, hypotonia, nystagmus, and rarely spontaneous bleeding.

A type of migraine in which there is an aura characterized by focal neurological phenomena that usually proceed, but may accompany or occur in the absence of, the headache. The symptoms of an aura may include fully reversible visual, sensory, and speech symptoms but not motor weakness. Visual symptoms may include flickering lights, spots and lines and/or loss of vision and/or unilateral sensory symptoms such as paresthesias or numbness. At least one of the symptoms of an aura develops gradually over 5 or more minutes and/or different symptoms occur in succession.