External carotid artery aneurysm developing after embolization of a ruptured posterior inferior cerebellar artery aneurysm in a patient with cervicocephalic fibromuscular dysplasia--case report.

A 30-year-old man presented with an aneurysm of the left posterior inferior cerebellar artery manifesting as subarachnoid hemorrhage and cerebellar infarction. Angiography demonstrated string-of-beads sign typical of fibromuscular dysplasia (FMD) in the extracranial carotid and vertebral arteries. The aneurysm and the parent artery were successfully embolized with Guglielmi detachable coils. Severe vasospasm developed 1 week after admission, and was treated several times by selective injection of vasodilator. A new aneurysm of the left external carotid artery became evident 1 month later, whereas only slight dilation had previously been apparent. This angiographic sequence demonstrated a new arterial dissection. Despite the possibility of damage to the artery during multiple catheterizations, arterial wall changes caused by FMD appear to have been primarily responsible. This case emphasizes the need for particular care in performing vascular interventional procedures in the presence of FMD.