Delayed exacerbation of third nerve palsy due to aneurysmal regrowth after endovascular coil embolization.

A 72-year-old woman with a painful left third cranial nerve palsy due to a basilar artery aneurysm situated between the superior cerebellar and posterior cerebral arteries was treated with Guglielmi detachable coils (GDCs). Despite a good initial angiographic result with a small residual neck and improvement in the ocular motility and pain, the patient experienced worsening of the third cranial nerve palsy 15 months later. Cerebral angiography confirmed coil compaction with aneurysmal regrowth. A second endovascular coil embolization resulted in complete obliteration of the aneurysm. The patient experienced complete resolution of the pain and partial resolution of the third cranial nerve palsy. In some patients, a small residual aneurysm neck after endovascular embolization therapy with GDCs can result in delayed aneurysmal regrowth due to coil compaction. Clinical manifestations may herald this dangerous regrowth.