Fibromuscular Dysplasia

KEY FACTS

TERMINOLOGY

• Fibromuscular dysplasia (FMD)

○ Arterial disease of unknown etiology

○ Overgrowth of smooth muscle, fibrous tissue

○ Affects medium/large arteries

IMAGING

• Renal artery is most common overall site (~ 75%)

• Cervicocranial FMD (~ 70%)

○ Internal carotid artery (ICA) (30-50%) > external carotid

artery > vertebral arteries (10-20%)

○ Carotid bifurcation is typically spared

○ > 50% of cases are bilateral

○ Intracranial rare (supraclinoid ICA, middle carotid artery)

• CTA

○ Arterial luminal irregularity or "beading" ± stenosis or

aneurysm (rare)

• DWI-MR

○ Most sensitive for ischemic sequela of FMD

• DSA

○ Type 1 (85%): Classic "string of beads" = medial

fibroplasia

○ Type 2 (10%): Long, tubular stenosis = intimal fibroplasia

○ Type 3 (5%): Asymmetric outpouching from 1 side of

artery = periadventitial fibroplasia

TOP DIFFERENTIAL DIAGNOSES

• Atherosclerosis

• Standing waves

• Nonatherosclerotic vasculopathies

CLINICAL ISSUES

• Symptoms: hypertension, stroke, dissection

• Treatment

○ Antiplatelet ± anticoagulant Rx to reduce risk of

thromboembolic sequela (stroke)

○ Balloon angioplasty

○ Covered stent, arterial reconstruction for aneurysm

(Left) Sagittal CTA shows

classic fibromuscular dysplasia

(FMD) in a 40-year-old woman

following trauma. There is

type I FMD in the cervical

carotid artery with alternating

areas of constriction and

dilatation ﬇. C1-C2 is the

most common location. Note

the typical sparing of the

carotid bulb st. (Right)

Carotid bifurcation shows

principal subtypes of FMD.

Type 1 appears as alternating

areas of constriction and

dilatation ſt, type 2 as

tubular stenosis st, and type 3

as focal corrugations ±

diverticulum ﬇.

(Left) Oblique DSA of the left

carotid artery shows ASVD

stenosis of the carotid bulb

﬊. Mural calcification is faint

subtraction artifact ﬉.

Superiorly, the internal carotid

artery (ICA) shows luminal

irregularity and beading,

consistent with FMD ſt.

Additional FMD involvement

of an external carotid artery

branch is evident ﬈. (Right)

Lateral DSA after carotid

stenting across the ASVD

stenosis ﬉ shows a distal

protection device in situ ﬈.

Note the irregularity of the

ICA ſt and occipital artery ﬊

due to FMD.

Trauma, and Stroke

Brain: Pathology-Based Diagnoses: Malformations,

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