5. a major complication during the endovascular coiling procedure, such as massive intracranial bleeding, intracranial thromboembolism, coil migration, aneurysm perforation or rupture, arterial dissection, major arterial occlusion, a large territorial cerebral infarct defined as involving > 1/3 of a vascular territory, or a new major neurological deficit post-procedure (e.g., hemiplegia or aphasia lasting > or = 12 hours post-aneurysm coiling)*.