How do I diagnose and treat fibromuscular dysplasia of the internal carotid artery in a young woman presenting with hypertension, a neck bruit, and transient ischemic attacks?

Fibromuscular Dysplasia of the Internal Carotid Artery

Diagnosis

In a young woman presenting with hypertension, neck bruit, and TIAs, immediately obtain contrast-enhanced CTA or MRA from head to pelvis to confirm carotid FMD and assess for systemic involvement. 1

Key Diagnostic Imaging Strategy

• First-line imaging: Contrast-enhanced CTA or MRA extending from head to pelvis is Class I recommended to diagnose carotid FMD and evaluate other arterial territories simultaneously 1
• Pathognomonic finding: The "string-of-beads" pattern (beads larger than normal arterial diameter) confirms medial fibroplasia, which accounts for 80-85% of FMD cases 1, 2
• Location matters: Carotid FMD characteristically involves the mid-to-distal segments of the internal carotid artery bilaterally, distinguishing it from atherosclerosis which affects proximal/ostial segments 1, 2
• Duplex ultrasonography can detect flow abnormalities but is less reliable for morphologic diagnosis compared to cross-sectional imaging 1
• Catheter angiography is reserved for cases with high clinical suspicion despite inconclusive non-invasive studies 3, 1

Additional Imaging Findings to Identify

• Focal concentric or tubular stenosis (suggests intimal fibroplasia subtype) 1
• Arterial elongation, kinking, coiling, weblike lesions, or aneurysmal dilation 3, 1
• Dissection features: intramural hematoma, dissection flap, or pseudoaneurysm 1
• Concurrent brain MRI or CT should be performed, as 50-95% of carotid dissection patients develop cerebral or retinal ischemia 1

Screen for Complications

• Intracranial aneurysms: Screen for subarachnoid hemorrhage risk, as aneurysms are a recognized complication 3, 2
• Dissection risk: Approximately 12-15% of carotid FMD patients develop spontaneous arterial dissection 1, 4
• Evaluate for cranial nerve IX-XII palsies and Horner syndrome (ptosis, miosis, anhidrosis) 1, 2

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Treatment Algorithm

For Symptomatic Carotid FMD (TIA/Stroke)

Initiate antiplatelet therapy immediately (aspirin or clopidogrel) and reserve percutaneous angioplasty with or without stenting for patients with recurrent ischemic symptoms despite optimal medical management. 1, 4

Step 1: Immediate Medical Therapy

• Antiplatelet therapy: Start aspirin or clopidogrel immediately for all symptomatic patients 1, 4
• Blood pressure control: Target <140/90 mmHg using ACE inhibitors, ARBs, or calcium channel blockers 4
• Beta-blockers or non-dihydropyridine calcium channel blockers (verapamil, diltiazem) may theoretically reduce arterial wall stress, though effectiveness remains unproven (Class IIb evidence) 3

Step 2: Assess for Dissection

• If dissection is present with ischemic symptoms, initiate 3-6 months of antithrombotic therapy (Class IIa) 3, 1:
  • Option 1: Anticoagulation (heparin/LMWH → warfarin) yields ~1% stroke/death at 3 months 1
  • Option 2: Antiplatelet therapy (aspirin, clopidogrel, or aspirin-dipyridamole) yields ~2% stroke/death at 3 months 1
• After 3-6 months, transition all patients to lifelong antiplatelet therapy 1

Step 3: Consider Revascularization

• Indication: Recurrent ischemic events (TIA or stroke) despite optimal antiplatelet therapy 3, 1
• Preferred method: Percutaneous transluminal angioplasty with or without stenting (Class IIb for dissection with persistent symptoms) 3, 1
• Both surgical revascularization and endovascular approaches have been successful, though evidence is limited to case series (Level C) 3, 5

For Asymptomatic Carotid FMD

Revascularization is NOT recommended for asymptomatic carotid FMD regardless of stenosis severity (Class III: No Benefit). 3, 4

• Medical management only: Antiplatelet therapy (aspirin or clopidogrel) for all asymptomatic patients 1, 4
• Sequential imaging surveillance: CTA or MRA annually for the first year, then at extended intervals once stability is documented 1

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Surveillance Protocol

• Initial surveillance: Annual non-invasive imaging (CTA or MRA) of carotid arteries for the first year to detect disease progression, new dissection, or aneurysmal change 1, 2
• Long-term surveillance: Reduce imaging frequency once stability is confirmed over time 1, 2
• Dissection follow-up: Vascular imaging at 1 month, 6 months, then annually to monitor vessel healing and patency 1

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Critical Pitfalls to Avoid

• Do not assume atherosclerosis in young women with carotid stenosis; bilateral involvement, mid-to-distal location, and beading pattern distinguish FMD 1, 2
• Do not revascularize asymptomatic lesions regardless of stenosis severity—this is a Class III (No Benefit) recommendation 3, 4
• Maintain high suspicion for dissection in ~15% of patients—new neck pain, Horner syndrome, or worsening neurologic deficits warrant urgent evaluation 1, 2
• Do not overlook systemic involvement—FMD is a systemic arteriopathy requiring comprehensive vascular evaluation from head to pelvis at diagnosis 1, 4
• Symptoms arise from two mechanisms: (1) reduced cerebral perfusion from stenosis and (2) thromboembolism from irregular arterial surfaces serving as platelet-adhesion sites 3, 2

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Additional Risk Factor Management

• Statin therapy: Recommended for patients who have suffered ischemic stroke, with goal LDL <70 mg/dL 1
• Smoking cessation: Provide counseling to all patients who smoke 1
• Hypertension control: Essential to prevent arterial dissection, which can occur in multiple vascular territories 4