Splitting of the oculomotor nerve by the posterior communicating artery--case report.

A 62-year-old woman presented with subarachnoid hemorrhage manifesting as sudden onset of headache, but without visual symptoms or extraocular movement disturbances. Computed tomography angiography showed a 7-mm size aneurysm originating from the internal carotid-posterior communicating artery (PcomA). After the neck of the aneurysm was clipped, the PcomA was confirmed to have split the oculomotor nerve. Splitting of the oculomotor nerve by the PcomA was probably caused by arterial blood pulsation in the tortuous PcomA.