Transient alpha coma following minor head trauma in a patient with primitive trigeminal artery.

A 26-year-old male presented with transient alpha coma following minor head trauma after a traffic accident. His consciousness disturbance suddenly recovered 3.5 hours later. He had not suffered cardiac arrest before admission, nor was taking any drugs. Magnetic resonance (MR) angiography 6.5 hours after consciousness recovery disclosed persistent primitive trigeminal artery (PTA) with minor segmental narrowings. Three months later, MR angiography revealed that both the PTA and the distal basilar artery were slightly diated without evidence of narrowing. Conventional angiography and single photon emission computed tomography revealed that the distal basilar artery was supplied mainly by the PTA. Transient circulatory disturbance due to traumatic angiospasm of the PTA may have caused hypoperfusion of the upper brainstem in this patient.