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Intracranial Atherosclerosis


KEY FACTS

Terminology

  • Intracranial atherosclerotic vascular disease (ASVD)

  • Intracranial atherosclerotic stenosis (ICAS)

Imaging

  • Gold standard is now high-resolution MR (HRMR) with direct vessel wall imaging

    • HRMR vessel wall imaging > > depicting lumen (DSA, CTA, MRA)

  • Imaging findings (HRMR)

    • Crescent-shaped or eccentric thickening

    • May show asymmetric hyperintensity of intraplaque hemorrhage on T1WI

    • Noncircumferential, short segment, irregular enhancement

  • CTA/MRA/DSA

    • Visualizes lumen, not wall

    • Warfarin-aspirin symptomatic intracranial disease method for calculating ICAS

      • –

        % stenosis = [1- (diameter stenosis/diameter normal)] x 100

    • Focal stenosis, luminal irregularities in cortical vessels can mimic vasculitis

      • –

        Most common cause of vasculitic-like appearance at angiography in middle-aged/older patient is intracranial ASVD

Top Differential Diagnoses

  • Vasculitis/arteritis

  • Vasospasm

  • Dissection

  • Nonocclusive thrombus or embolus

Clinical Issues

  • Disease burden of intracranial ASVD greatly underestimated

  • Most common cause of intracranial vascular stenosis in adults

  • Independent correlation with T2/FLAIR hyperintensities

  • Poor prognosis with progressive disease unless treated aggressively

Coronal graphic shows atherosclerotic plaques (ASVD)
involving the major intracranial arteries and their branches. Inset shows penetrating (lenticulostriate) arteries
and lacunar infarcts
. ASVD plaques are typically short segment, irregular, noncircumferential, and may enhance.

DSA in a 68-year-old man in the ER with an acute stroke shows extensive intracranial ASVD. Note multiple areas of stenosis
. An ulcerating plaque
is also present in the supraclinoid internal carotid artery.

Axial T2WI shows a typical pontine perforating artery infarct
. The basilar artery “flow void”
appears normal.

Vessel wall imaging with thin-section 3T T1 C+ FS MR in the same patient shows enhancement of the subacute infarct
. A partial rim of crescentic enhancement in the basilar artery wall is also present
, consistent with chronic inflammation within an ASVD plaque.

TERMINOLOGY

Abbreviations

  • Intracranial atherosclerotic vascular disease (ASVD)

  • Intracranial atherosclerotic stenosis (ICAS)

Definitions

  • Narrowing or ectasia of intracranial arteries secondary to ASVD

IMAGING

General Features

  • Best diagnostic clue

    • ASVD plaque in vessel wall directly visualized with high-resolution MR (HRMR)

      • –

        HRMR vessel wall imaging >> depicting lumen (DSA, CTA, MRA)

      • –

        Crescent shaped or eccentric thickening

      • –

        ± intraplaque hemorrhage, enhancement

    • Stenotic intracranial artery on CTA/MRA/DSA

      • –

        Visualizes lumen, not wall

    • Less common: Dolichoectasia

      • –

        Enlargement/tortuosity without stenosis

  • Location

    • Distal basilar artery (BA), cavernous/supraclinoid ICA most common

    • Less common sites

      • –

        Circle of Willis (COW)

      • –

        MCA rare (2% of cases) but high stroke risk

  • Morphology

    • Usually eccentric, irregular thickening ± ulceration, hemorrhage

CT Findings

  • NECT

    • Mural Ca++

  • CTA

    • MDR CTA has high sensitivity/specificity

      • –

        In patients with > 50% stenosis or occlusion of large arteries

      • –

        Caveat: Mural Ca++ may ↓ specificity

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