Giant aneurysm at the junction of the left internal carotid and persistent primitive trigeminal arteries--case report.

A 67-year-old female presented with an unruptured giant aneurysm at the junction of the left internal carotid artery (ICA) and the persistent primitive trigeminal artery (PTA), manifesting as progressive left abducens nerve paresis. The PTA was clipped by the left suboccipital approach. The aneurysm was then successfully thrombosed by ligation of the left ICA at the cervical portion following left superficial temporal artery-middle cerebral artery anastomosis. The left abducens nerve paresis improved postoperatively. Magnetic resonance imaging was of considerable value in the pre- and postoperative evaluation of the giant aneurysm.