In a woman under 50 presenting with unexplained transient ischemic attacks and a neck bruit, how should carotid fibromuscular dysplasia be diagnosed and managed?

Carotid Fibromuscular Dysplasia: Diagnosis and Management

Diagnostic Approach

In a woman under 50 with unexplained TIAs and a neck bruit, use contrast-enhanced CTA or MRA as the primary diagnostic modality to confirm carotid fibromuscular dysplasia, looking for the characteristic "string of beads" appearance or focal stenosis. 1, 2

Initial Imaging Strategy

• CTA or MRA from head to pelvis should be performed at diagnosis to identify the systemic nature of FMD, as it commonly affects multiple vascular territories including renal, vertebral, and other arteries 2
• Contrast-enhanced CTA, MRA, and catheter-based contrast angiography are all Class I useful modalities for diagnosis 1
• Catheter angiography remains the gold standard and should be performed when clinical suspicion is high and noninvasive tests are inconclusive 2, 3
• Duplex ultrasonography may identify flow abnormalities but is less reliable for morphologic diagnosis compared to cross-sectional imaging 1, 3

Key Diagnostic Features to Identify

• The "string of beads" pattern is pathognomonic for medial fibroplasia (the most common subtype, accounting for 80-85% of cases), where the diameter of the beading exceeds the normal arterial diameter 2, 4
• Focal, concentric, or tubular stenosis suggests intimal fibroplasia, which mimics atherosclerotic narrowing 1, 2
• Look for arterial elongation, kinking, coiling, weblike lesions, or aneurysmal dilation 1, 2
• FMD typically affects the middle and distal portions of the internal carotid artery bilaterally, unlike atherosclerosis which affects proximal segments 1, 2

Associated Complications to Screen For

• Approximately 15% of patients with carotid FMD have associated arterial dissection, which can occur spontaneously 1, 2
• Screen for Horner syndrome (ptosis, miosis, anhidrosis), which indicates internal carotid artery dissection 5, 2
• Evaluate for cranial nerve palsies (IX-XII) and subarachnoid hemorrhage from aneurysmal rupture 1, 2
• Check for renal artery involvement, as hypertension is the hallmark presentation of systemic FMD 2

Management Strategy

For Symptomatic Patients (TIA/Stroke)

Initiate antiplatelet therapy immediately and consider percutaneous angioplasty with or without stenting for symptomatic carotid FMD causing recurrent ischemic events. 1

• Both surgical revascularization and endovascular approaches have been successful in alleviating ischemic symptoms 1, 4
• Percutaneous angioplasty with or without stenting is increasingly advocated based on case series, though no randomized trials compare it to surgery 1, 4
• Surgical options include graduated endoluminal dilation or resection, though these are less commonly used in contemporary practice 6, 7

Medical Therapy

• Antiplatelet therapy is the accepted standard for all patients with carotid FMD, even asymptomatic cases 1, 6
• For patients with associated arterial dissection and ischemic symptoms, antithrombotic treatment with either anticoagulation (heparin, LMWH, or warfarin) or antiplatelet agents (aspirin, clopidogrel, or extended-release dipyridamole plus aspirin) for 3-6 months is reasonable (Class IIa) 1
• If ischemic symptoms persist despite antithrombotic therapy after acute dissection, carotid angioplasty and stenting might be considered (Class IIb) 1

Surveillance Protocol

• Annual noninvasive imaging (CTA or MRA) of the carotid arteries is reasonable initially to detect progression, new dissection, or aneurysmal degeneration 2
• Imaging frequency may be reduced once stability has been confirmed over several years 2
• Sequential imaging is recommended even for asymptomatic patients to monitor disease extent 1

Critical Clinical Pitfalls

• Do not assume atherosclerotic disease in young women with carotid stenosis—the bilateral involvement, mid-to-distal location, and characteristic beading pattern distinguish FMD from atherosclerosis 1, 2
• Do not overlook the systemic nature of FMD—failure to screen other vascular beds (especially renal arteries) may miss treatable hypertension or other complications 2
• Recognize that 15% of carotid FMD patients will develop dissection, so maintain high suspicion for new neck pain, Horner syndrome, or worsening neurologic symptoms 1, 2
• The pathophysiology and natural history remain poorly understood, but symptoms result from either reduced blood flow or thromboembolism from the irregular arterial surface 1