Fibromuscular dysplasia of the internal carotid circulation: an unusual presentation.

Fibromuscular dysplasia (FMD) is an arterial disease of unknown etiology. Most often it affects the renal and internal carotid arteries (ICA), although any artery can be involved. Internal carotid arteries are affected in 25-30% of patients. When carotid arteries are involved, cervical segments C1-C2 are most often affected. FMD of intracranial arteries is rare. FMD has been associated with intracranial aneurysms in 7-50% cases, but FMD associated with a giant (> 2.5 cm) intracranial aneurysm is rare. Extracranial internal carotid aneurysms are uncommon, with only 3% caused by FMD. We report a case of intra and extracranial FMD associated with a giant intracranial aneurysm and an aneurysm of the right extracranial ICA.