Tic douloureux caused by primitive trigeminal artery or its variant.

Primitive trigeminal artery (PTA) is an extremely rare cause of tic douloureux. None of the reports on PTA variant, which is an anomalous cerebellar artery arising from the internal carotid artery without anastomosis to the basilar artery, has suggested the possibility of this vessel causing tic douloureux. Eight cases of tic douloureux are reported in which a PTA or PTA variant was found during microvascular decompression (MVD). These cases were derived from a series of 1257 patients treated with MVD for tic douloureux. In one patient, the neuralgia was caused by a combination of vessels: a PTA, the superior cerebellar artery, and the anterior inferior cerebellar artery. In the other seven cases, a PTA variant was compressing the root entry zone of the trigeminal nerve. All eight patients gained excellent pain relief after MVD of the root entry zone. The significance of PTA's and PTA variants as the cause of tic douloureux and the effectiveness of MVD in the management of such cases are discussed.