Case 14

Discussion:

Fibromuscular dysplasia (FMD) is an arterial disease of unknown etiology affecting medium and large arteries typically in young and middle-aged women. It has been described in association with alpha-1 antitrypsin deficiency. It typically affects the renal arteries in 85% of the cases and often presents with  renovascular hypertension. The second most common site is the ICA, often bilateral( 65%) and may present as cerebral ischemia (20%), transient ischemic attack (29%), or thromboembolic stroke (6%). FMD has been associated with intracranial aneurysms in about 30% of the cases and spontaneous carotid artery dissection in 10-20%. About a third of patients with carotid FMD also have renal artery FMD and 10% have vertebral artery involvement. Other arteries potentially affected by FMD include lumbar, mesenteric, celiac, hepatic, and iliac arteries.

Although angiography is the gold standard, CT angiography (CTA) and MR angiography (MRA) are the imaging modalities of choice, showing typical string of beads appearance.

The 3 angiographic appearances are described:

• Type 1:  80-85% of cases. Typical string of beads appearance with alternating segments of stricture and dilation. Usually result of medial fibroplasia of the arterial wall.
• Type 2: 6-12% of cases with arterial fibroplasia, presenting as a long tubular stenosis. This can be associated with any histologic types but most frequently seen with the intimal form. The differential diagnosis for a long tubular narrowing of the internal carotid artery includes dissection, arteritis, congenital hypoplasia, vasospasm, and narrowing secondary to decreased inflow or outflow from the carotid artery secondary to proximal or distal stenotic lesions.
• Type 3: 4-6% and is characterized by involvement of only one side of an artery. Appearing as a diverticularizations of the vessel wall. The type is often difficult to distinguish from atherosclerotic ulceration or a pseudoaneurysm.

References:

• Fibromuscular Dysplasia Society of America