Trigeminal neuralgia associated with tentorial agenesis and temporal lobe herniation--case report.

A 22-year-old female presented with an extremely rare case of trigeminal neuralgia associated with tentorial agenesis. The pulsating pain in her left maxillary region persisted for an abnormally long time and had no trigger zone. The pain later spread to the periorbital region. Coronal magnetic resonance imaging revealed left medial temporal lobe herniation caused by tentorial agenesis. The herniated temporal lobe, which had distorted the superior cerebellar artery, was causing compression of the trigeminal nerve. Her condition improved following microvascular decompression surgery. Tentorial agenesis should be considered as a cause of atypical pulsating facial pain, especially in younger patients.