John R. Gaughen, Jr., M.D.

May 10, 2005

Discussion

Fibromuscular dysplasia (FMD) is a vasculopathy affecting the medium and large arteries. Occurring primarily in young or middle-age women, it most commonly affects the renal arteries, where it ranges from an asymptomatic lesion to a cause of refractory hypertension. The carotid arteries are the second most commonly affected site, causing a variety of abnormalities ranging from asymptomatic to stroke. Carotid FMD has an association with both intracranial aneurysms and spontaneous carotid dissection. There are three histologic subtypes of FMD, intimal fibroplasia, medial fibroplasia, and subadventitial fibroplasias. The most common form, medial fibroplasias, causes the classic "string of beads" appearance of alternating segments of stenosis and dilatation. In contrast, the intimal form has a propensity for causing long, tapered narrowing. Ultrasound, CTA, MRA, and catheter angiography all play a role in the detection of FMD, with catheter angiography currently the gold standard. Ultrasound has a relatively low sensitivity, especially in asymptomatic patients. As shown in this case, ultrasound may demonstrate a focal or segmental area of stenosis, manifest as a high velocity jet (aliasing on these images), high resistive index, and tardus-parvus waveform downstream. Catheter angiography offers both diagnostic and therapeutic benefits. Currently, therapy depends on the patient's symptomatology. Asymptomatic patients can be managed expectantly, while percutaneous transluminal angioplasty (PTA) is an effective treatment for symptomatic patients. As in this case, PTA alone often offers effective and durable results. Adjunctive stenting may be necessary in complicated cases. Because of the efficacy and minimally-invasive nature of PTA, surgery has been relegated to a second-line treatment.

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