PERSISTENT TRIGEMINAL ARTERY - AN ANATOMIC STUDY

INTRODUCTION: The most frequent embryonic communication between the ve rtebrobasilar and carotid systems is a persistent trigeminal artery (P TA). It has been observed in 0.1 to 0.2% of cerebral angiograms. We fo und this variation in an anatomic specimen, and after microscopic diss ection, we performed an analysis of the course of the PTA and its rela tionship with the abducens nerve and the meningohypophyseal trunk. MET HOD: A PTA was incidentally encountered in an injected cadaver specime n during a transpetrosal approach. This embryonic variation and its an atomic relationship are discussed. RESULTS: The PTA can take either a lateral or medial course regarding its relationship with the abducens nerve. When the PTA originates from the posterolateral aspect of the p osterior bend of the cavernous carotid artery (C4 segment), it crosses underneath and distorts the abducens nerve, continuing between the ab ducens and trigeminal nerves. When taking a medial course, the PTA ari ses from the posteromedial aspect of the posterior bend of the caverno us carotid at the same segment and pierces the clival dura at the dors um sellae. Cranial nerve displacement or distortion is less likely in this variation. In an analysis of carefully described anatomic studies , the PTA and meningohypophyseal trunk were found arising from either common or separated origins. CONCLUSION: The most frequent embryologic al anastomosis between the carotid and vertebrobasilar system is the P TA. Its course and relationship with the cranial nerves may determine its clinical presentation.