Oculomotor nerve palsy presumably caused by cisternal drain during microsurgical clipping

BACKGROUND: Oculomotor nerve palsy can be caused by diverse etiologies, but no report has yet documented its association with a cisternal drain. CASE DESCRIPTION: A 35-year-old woman presented with severe headache. The patient did not exhibit oculomotor nerve palsy at presentation. Cranial computed tomography (CT) revealed diffuse subarachnoid hemorrhage. The patient underwent open microsurgical clipping of a ruptured middle cerebral artery aneurysm. During surgery, a cisternal drain was placed in the basal cistern at the medial aspect of the clinoidal portion of the internal carotid artery. The patient presented with the left oculomotor nerve palsy immediately after surgery. CT revealed displacement of the cisternal drain to the lateral aspect of the anterior clinoid process. The patient’s mydriasis and sluggish light reaction recovered after 7 days, while extraocular movements persisted for 50 days. The constructive interference steady-state sequence detected the left oculomotor nerve coursing adjacent to the clinoidal internal carotid artery. CONCLUSION: Oculomotor nerve palsy can be caused by collision with a thin silastic tube placed during surgery for aneurysmal subarachnoid hemorrhage. Withdrawal of the drain as early as possible is recommended when drain-associated oculomotor nerve palsy is suspected.