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Atherosclerotic Vascular Disease (ASVD) Fusiform Aneurysm


KEY FACTS

Terminology

  • Atherosclerotic vascular disease fusiform aneurysm (ASVD FA)

  • ASVD → abnormal dilation, tortuosity of intracranial arteries

  • Aneurysms with separate inflow, outflow ostia

Imaging

  • Exaggerated arterial ectasia(s) + focal fusiform/saccular enlargement

    • Long segment irregular fusiform or ovoid arterial dilatation

    • Usually large (> 2.5 cm), may be giant

    • Vertebrobasilar > carotid circulation

  • CT: Hyperdense, Ca++ common

    • May present as CPA mass

  • MR: Signal varies flow, presence/age of hematoma

    • Lumen, intramural clot often heterogeneous

    • Residual lumen enhances; intramural clot does not

    • Prominent phase artifact common

  • Noncontrast 3D TOF inadequate due to flow saturation, phase dispersion

  • Dynamic contrast-enhanced MRA for aneurysm delineation, T2 for brainstem delineation

Clinical Issues

  • Peak age: 7th to 8th decades

  • Presentation: Ischemic stroke > compressive symptoms (cranial neuropathy)

  • Unlike saccular aneurysms, rupture with subarachnoid hemorrhage and headache rare

Diagnostic Checklist

  • DSA or contrast-enhanced CTA/MRA necessary to delineate patent lumen

  • Slow/complex flow in residual lumen → heterogeneous signal

  • Consider dissecting aneurysm, non-ASVD etiology if younger patient

Autopsy shows a tortuous vertebrobasilar artery with an atherosclerotic vascular disease (AVD) fusiform aneurysm that extends from the vertebral artery junction
to the distal basilar bifurcation
.

(Courtesy R. Hewlett, MD.)

Oblique DSA in same patient 2 yr later shows dolichoectasia of the proximal distal vertebral arteries
. A fusiform ASVD aneurysm lies between the arterial ectasias; residual lumen is indicated
, and aneurysm had enlarged but partially thrombosed, leading to mild TIAs.

NECT scan shows typical hyperdense atherosclerotic fusiform aneurysm
with mural calcifications
. Note extensive calcification of the internal carotid, right middle cerebral arteries
.

Series of MRs shows the bizarre appearance of classic atherosclerotic fusiform vertebrobasilar aneurysm
.

(Courtesy M. Hartel, MD.)

TERMINOLOGY

Abbreviations

  • Atherosclerotic fusiform aneurysm (ASVD FA)

Synonyms

  • Giant fusiform aneurysm, megacolichobasilar artery

Definitions

  • ASVD → abnormal dilation, tortuosity of intracranial arteries

    • Aneurysms with separate inflow, outflow ostia

IMAGING

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