eMedicine Specialties > Radiology > Vascular/Interventional

Fibromuscular Dysplasia (Carotid Artery)

Author: Jeffrey P Kochan, MD, Professor of Radiology and Neurosurgery; Director of Diagnostic and Interventional Neuroradiology, Department of Radiology, Temple University Hospital
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Updated: Nov 13, 2008

Introduction

Background

Fibromuscular dysplasia (FMD) is an arterial disease of unknown etiology typically affecting the medium and large arteries of young to middle-aged women. This article focuses on FMD of the carotid arteries.¹

Presentation

Demographics

• Fibromuscular dysplasia typically occurs in persons 25-50 years of age.
• For fibromuscular dysplasia, the male-to-female ratio is 1:3.
• The reported incidence of fibromuscular dysplasia in adults is 0.6%, as determined by angiography; the incidence is 1.1%, as determined by autopsy.

Natural history and presentation

Although the etiology of FMD is unknown, studies have described an association with alpha-1 antitrypsin deficiency.⁸ Other etiologic factors suspected of having a role in the pathogenesis of FMD include hormonal effects on smooth muscle, mechanical stress on the wall of affected arteries, and mural ischemia in the dysplastic vessels.

First described by Leadbetter and Burkland in 1938, fibromuscular dysplasia (FMD) is an arterial disease typically affecting the renal arteries in 85% of patients; patients often present with renovascular hypertension. The internal carotid artery is the second most common location. The internal carotid artery is affected bilaterally in 65% of cases; patients may present with cerebral ischemia (20%), transient ischemic attack (29%), or thromboembolic stroke (6%). FMD has been associated with intracranial aneurysms in as many as 30% of patients and spontaneous carotid artery dissection in 10-20%. One third of patients with carotid FMD also have renal artery FMD; in 10% of patients, the vertebral artery is involved. Other arteries potentially affected by FMD include the lumbar, mesenteric, celiac, hepatic, and iliac arteries.^2,3,4,5,6,7

FMD may present as a transient ischemic attack or thromboembolic stroke as a result of thrombogenic tandem stenoses or carotid artery dissection. FMD has been associated with intracranial aneurysms; the diagnosis should be considered in patients who present with intracranial hemorrhage. Patients with carotid FMD also may have renal artery FMD and, less commonly, FMD of the lumbar, mesenteric, celiac, hepatic, and iliac arteries. If FMD is encountered anywhere in the circulation, the carotid arteries should be evaluated.

Histologically, FMD has been classified into 3 distinct types: intimal fibroplasia, medial fibroplasia, and subadventitial (perimedial) fibroplasia of the arterial wall. The different types of FMD are not easily differentiated by findings on angiography. The medial type of FMD is by far the most common; medial FMD is classically diagnosed on the basis of a "string of beads" appearance on angiography. This appearance is explained by the presence of luminal stenosis alternating with aneurysmal outpouchings. Classically, the intimal form of FMD is associated with smooth focal stenoses on angiography.


Treatment

The principal risk of fibromuscular dysplasia, as with any occlusive disorder affecting the cervicocerebral arterial circulation, is thromboembolism. Many patients with documented FMD have no symptoms. Surgical treatment or percutaneous transluminal balloon angioplasty is indicated only for those patients with symptomatic carotid arterial disease. FMD, when it produces minimally stenotic lesions — even those affecting a long segment of vessel — may be managed conservatively with antiplatelet therapy, anticoagulant therapy, or both.

Historically, the management of FMD with severely stenotic symptomatic lesions and angiographically static flow in a dilated segment has been surgical. Options have included arterial resection with a saphenous interposition graft or intraoperative intra-arterial dilation with graduated rigid dilators. Surgical excision of carotid FMD is more complex technically, usually requiring mandibular disarticulation to access the upper cervical segment of the internal carotid artery most commonly affected.⁹

Currently, with advances in balloon catheters and imaging-systems technology, percutaneous transfemoral angioplasty (PTA), without or with stenting, has become an effective option for the treatment of patients with hemodynamically significant stenoses; it provides excellent results in a minimally invasive fashion. Because the intima of the affected arteries is abnormal, angioplasty alone may result in dissection and occlusion. When performing PTA, the operator must be prepared to place stents, should these complications occur. Note that in the renal arteries, angioplasty alone (ie, without stents) typically provides good and durable results without thrombosis. For renal arteries, PTA alone is generally the treatment of choice for medial fibroplasia causing renovascular hypertension.

The long-term outcome of the use of endovascular stents in the treatment of carotid FMD lesions is unknown. Currently, no stents have been approved by the FDA for carotid indications, whether for atherosclerotic lesions, recurrent stenoses after surgery, or FMD.

Differential Diagnoses

Arteritis, Takayasu
Carotid Artery, Stenosis

Other Problems to Be Considered

Arteritis
Carotid artery, dissection
Pseudoaneurysm
Vasospasm

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