Reduced internal carotid artery caliber - normal variant

Case contributed by Sagar Tomar
Diagnosis certain


Acute onset vertigo

Patient Data

Age: 40 years
Gender: Male

MR angiogram brain and neck


MR angiogram time of flight (TOF) neck and brain reveals mild generalized reduction in caliber of the left ICA (axial, coronal) attributable to the vessel only supplying the left MCA, as there is hypoplasia or abesence of the left A1 segment of ACA (a common finding). In contrast, the right ICA supplies both ACA territories and the right MCA and is thus correspondingly larger.

Case Discussion

The caliber of the internal carotid artery should be commensurate with the territory it supplies. Thus, in this instance, as a result of a hypoplastic or aplastic A1 segment, the left ICA is smaller than the right. This should not be confused with pathology.

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