Occlusion of internal carotid artery and formation of anterior communicating artery aneurysm in cervicocephalic fibromuscular dysplasia--follow-up case report.

A 44-year-old female with cervicocephalic-fibromuscular dysplasia (FMD) suffered a subarachnoid hemorrhage 10 years after presenting with left impaired extraocular movement. Carotid and vertebral angiography had shown string-of-beads sign in the left external carotid artery and fusiform aneurysms in the left carotid cavernous portion and in the left vertebral artery. On admission, the left carotid angiogram showed complete occlusion of the left internal carotid artery and the right carotid angiogram showed a new anterior communicating artery aneurysm. The territory of the left middle cerebral artery was supplied from the right internal carotid artery via the anterior communicating artery and from the basilar artery via the posterior communicating artery. Occlusion of the main arteries is rare in the clinical course of FMD. We suggest that hemodynamic stress due to occlusion of the internal carotid artery contributed to formation of the anterior communicating artery aneurysm, possibly associated with intrinsic changes of the arterial wall induced by FMD.