A very unusual case of fibromuscular dysplasia with multiple aneurysms of the vertebral artery and posterior inferior cerebellar artery.

Fibromuscular dysplasia (FMD) is a noninflammatory and nonatheromatous arteriopathy that commonly affects the renal and cervical internal carotid arteries and sometimes the vertebral arteries (VAs). The association of FMD with intracranial aneurysms is widely known. The authors describe a rare case of FMD presenting with subarachnoid hemorrhage due to the rupture of 1 of 10 aneurysms located in the extra- and intracranial vertebral and posterior inferior cerebellar arteries. The FMD was treated successfully using flow reversal therapy, consisting of proximal occlusion of the VA with Guglielmi detachable coils, and was diagnosed histopathologically using a biopsy specimen of the distal superficial temporal artery. Originally FMD may be caused by a fragile arterial wall that may progress to the formation of an aneurysm due to hemodynamic stress. For this reason, FMD may be treatable by reducing this hemodynamic stress.