[Trigeminal neuralgia caused by tortuous vertebrobasilar system--the clinical and imaging features].

Ten (6.8%) out of 146 patients with trigeminal neuralgia (TN) who underwent SPGR-MRI and 3D-TOF-MRA from August 1993 to October 1996, were found to have vascular compression caused by a tortuous vertebrobasilar system (TVBS). They were mostly males, demonstrated left-sided predominance, and had ipsilateral hemifacial spasm, compared with other 52 patients whose offending arteries were either superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA)or posterior inferior cerebellar artery (PICA). The patients who showed vascular compression by TVBS, presented an artery which compresses and dislocates the rootentry zone (REZ) of the trigeminal nerve, presses the brain stem at REZ and simultaneously compresses the REZ of the facial nerve. In addition, the diameters of the two branches of vertebrobasilar artery were not equal. These features indicate that the atherosclerotic change of the offending artery in TN caused by TVBS is more severe than that caused by SCA, AICA or PICA. This change causes an irregular running of artery which leads a strong compression of the trigeminal nerve REZ and of the brain stem. Consequently, the facial nerve REZ is severely affected leading to the presence of tic convulsif in TN caused by TVBS.