Direct clipping of a large basilar trunk aneurysm via the posterior petrosal (extended retrolabyrinthine presigmoid) approach--case report.

A 53-year-old female presented with an unruptured, large basilar trunk aneurysm manifesting only as headache with no neurological deficits, including absence of cranial nerve dysfunction. Cerebral angiography disclosed a large aneurysm with a wide neck arising from the midbasilar artery. We treated the aneurysm surgically via the posterior petrosal approach. Five angled clips were applied sequentially to the aneurysm and the basilar artery was successfully reconstructed. Electrophysiological monitoring was continued during the operation and showed no changes. Following the operation, the patient suffered from transient right abducens nerve palsy, which persisted for 3 months. Postoperative angiography showed that the aneurysm was obliterated, and the patency of the basilar artery was preserved.