Trigeminal neuralgia is a well-recognized disorder characterized by lancinating attacks of severe facial pain. The diagnosis of trigeminal neuralgia is based primarily on a history of characteristic pain attacks that are consistent with specific, widely accepted research and clinical criteria for the diagnosis. The cause of trigeminal neuralgia pain attacks is not known. However, the fact that benign tumors and vascular anomalies that compress the trigeminal nerve root can produce symptoms clinically indistinguishable from classic trigeminal neuralgia strongly implies that injury to the nerve root is an important initiating factor in the disease.