Does Fibromuscular Dysplasia Increase the Risk of Stroke?
Yes, fibromuscular dysplasia significantly increases stroke risk—approximately 9.8% of FMD patients experience stroke, 13.4% have TIA, and 12% develop cervical artery dissection, which itself is a major stroke mechanism. 1
Understanding the Stroke Risk in FMD
FMD is a nonatherosclerotic arterial disease that creates stroke risk through multiple mechanisms:
- Thromboembolic events occur when fibrous webs and irregular arterial surfaces serve as a nidus for platelet deposition, leading to embolic stroke or TIA 1
- Reduced cerebral blood flow results from arterial stenosis, occlusion, or the characteristic "string of beads" appearance caused by medial fibroplasia 1
- Arterial dissection develops spontaneously in approximately 12-15% of FMD patients, representing a critical stroke mechanism 2, 3
- Aneurysmal rupture can cause subarachnoid hemorrhage, though this is less common than ischemic events 1, 3
The cerebrovascular involvement predominantly affects the middle and distal portions of the internal carotid and vertebral arteries, typically at the level of the second cervical vertebra, distinguishing it from atherosclerotic disease which affects proximal segments 3, 4.
Epidemiologic Data from the US FMD Registry
The frequency of neurological events demonstrates clear stroke risk 1:
- 9.8% experienced stroke
- 13.4% had TIA
- 12% developed cervical artery dissection
- 5% experienced amaurosis fugax
Women are disproportionately affected, with FMD occurring predominantly in middle-aged females, though it can affect both genders at any age 1, 3.
Clinical Presentations That Signal Stroke Risk
Watch for these specific manifestations 3, 4:
- Unilateral head or neck pain suggesting cervical artery dissection
- Horner syndrome (ptosis, miosis, anhidrosis) from carotid involvement
- Cranial nerve palsies (particularly nerves IX-XII)
- Vertebrobasilar symptoms: headache, neck pain, vertigo, nausea, visual disturbances, or syncope
- Neck bruit in young women (<50 years) with unexplained TIA
Why FMD Causes Stroke: The Pathophysiology
The arterial wall changes in FMD create a prothrombotic environment 1:
- Medial fibroplasia (80-85% of cases) affects the musculature/media layer, creating the pathognomonic "string of beads" where the diameter of beading exceeds normal arterial diameter
- Multiple fibrous webs obstruct flow and serve as sites for platelet aggregation
- Arterial elongation, kinking, and coiling further compromise blood flow 2, 5
- Spontaneous dissection occurs due to weakened arterial walls
Critical Pitfall to Avoid
Never assume isolated cerebrovascular disease—FMD is a systemic arteriopathy requiring comprehensive vascular evaluation from head to pelvis at diagnosis, as multiple vascular beds are typically involved 2, 3. The presence of renal artery involvement (most common site) should prompt cerebrovascular screening, and vice versa.
Stroke Risk in Special Populations
Pediatric and young adult stroke: FMD is an important cause of stroke in children and young adults, with intracranial features more likely in this age group 6, 7. Cases have been reported in children as young as 3 years old with vertebral artery involvement 7.
Young women with unexplained stroke: In a 30-year-old female presenting with extensive MCA infarction, involvement of multiple supra-aortic trunks with irregular stenoses should immediately raise suspicion for FMD 8.
Quantifying the Risk: What the Evidence Shows
The 2021 AHA/ASA Stroke Prevention Guidelines explicitly recognize FMD as a stroke risk factor warranting dedicated management recommendations 1. The guidelines provide Class I (strongest) recommendations for antiplatelet therapy, blood pressure control, and lifestyle modification in FMD patients with prior stroke or TIA, acknowledging the established causal relationship between FMD and cerebrovascular events.
The most serious complications include hypoperfusion secondary to aneurysm, dissection, or arterial occlusion, which can lead to stroke, as well as subarachnoid hemorrhage from aneurysmal rupture 5.