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Extracranial Vertebral Artery Dissection


KEY FACTS

Terminology

  • Vertebral artery (VA) dissection

  • Irregularity of VA contour from intimal tear or subadventitial hematoma

Imaging

  • Stenoocclusive dissection

    • Dissection to subintimal plane with vessel luminal narrowing or occlusion

  • Dissecting aneurysm

    • Dissection into subadventitial plane with dilatation of outer wall

  • Intramural hematoma is pathognomonic

    • Best seen as bright crescent on T1 FS MR

  • CTA source images show contour changes of lumen

  • Conventional angiography is gold standard

Top Differential Diagnoses

  • Extracranial atherosclerosis

  • Fibromuscular dysplasia

  • Miscellaneous vasculitis

  • Congenital VA hypoplasia

Pathology

  • Traumatic VA dissection

    • Direct or indirect arterial injury

  • Spontaneous VA dissection

    • Many associations and predisposing factors

Clinical Issues

  • Age: Adults < 45 years

Diagnostic Checklist

  • Check other vessels carefully for 2nd dissection

  • Subadvential/intramural hematoma can sometimes occur without narrowing vessel lumen

  • Cerebellar infarction in young to middle-aged adults; need to exclude posterior inferior cerebellar artery infarction due to VA dissection

Axial CECT in a patient with idiopathic vertebral artery dissection demonstrates normal caliber of left vertebral artery
and narrowed, eccentric lumen of right vertebral artery
. Note normal and symmetric foramina transversarium.

Axial T1 FS MR in the same patient reveals a hyperintense crescent of mural hematoma
with small hypointense patent lumen. Contralateral vertebral artery shows no methemoglobin hyperintensity
. This is unilateral vertebral artery dissection.

Axial CTA shows rim enhancement of the left vertebral artery
with low-density mural hematoma and contrast filling the narrowed lumen
. Subtle linear lucency in the right vertebral artery proved not to be a dissection flap
.

Axial T2 MR in a patient with neck trauma and cervical fractures reveals traumatic vertebral artery dissection as loss of right vertebral flow void
, compared with the normal left side
. Note right cervical hemicord hyperintensity from cord ischemia
.

TERMINOLOGY

Abbreviations

  • Vertebral artery (VA) dissection

Definitions

  • Irregularity of VA contour from intimal tear or subadventitial hematoma

IMAGING

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