Oculomotor Nerve Palsy in a Patient with a Ruptured Middle Cerebral Artery Aneurysm

We describe a case of acute oculomotor nerve palsy caused by a ruptured middle cerebral artery (MCA) aneurysm. A 59-year-old female presenting with headache and nausea was admitted to our hospital. Her consciousness was alert, and had no other neurological deficit without left oculomotor nerve palsy. A computed tomography (CT) showed SAH extending from left sylvian cistern to basal cistern. CT angiography revealed a left MCA aneurysm which protruded toward internal carotid artery. The patient was successfully treated with surgical clipping. The oculomotor nerve palsy resolved immediately after the surgery. Perioperative radiological evaluation revealed that there were no evidence of midbrain hemorrhage or stroke, vessel anomaly of basilar, posterior cerebral or superior cerebellar artery, vasospasm, and uncal herniation. Furthermore, intraoperative findings revealed that the aneurysm was projected toward the affected carotid cistern and oculomotor nerve. From these findings and time course of oculomotor nerve palsy, it is suggested that the jet flow of bleeding from the ruptured MCA aneurysm caused oculomotor nerve palsy in the patient.