Incorporation of extruded coils into the third nerve in association with third nerve palsy

The extrusion of the coil complex outside of the aneurysmal dome is thought to be an important mechanism by which the aneurysm neck and fundus recanalize, but the migration of the coil loops and their incorporation inside vital nervous structures has not been clearly described. We reviewed the medical literature on coil extrusion and migration and report a rare case of third nerve palsy due to direct damage caused by coil loop migration that resolved after surgery. A 25-year-old woman presented with subarachnoid hemorrhage and painful left third nerve palsy. The angiogram revealed a supraclinoid internal carotid aneurysm incorporating the origin of the left posterior communicating artery. Her aneurysm was coiled. The 8 month follow-up angiogram revealed a major recurrence of her aneurysm. It was decided to surgically clip the aneurysm. At surgery, coil loops were found in the subarachnoid space and embedded into the third nerve. At 1 month follow-up she had recovered well, and only had very subtle diplopia upon fatigue. Coil extrusion is a fairly common phenomenon that should be suspected in instances of major aneurysmal recurrence. Surgical treatment is recommended, and special care should be taken when mobilizing the extruded coil mass.