A1 segment hypoplasia

Case contributed by Dr Abdulmajid Bawazeer

Presentation

Acute dizziness: to rule out an acute stroke

Patient Data

Age: 40 years
Gender: Male
MRI

Hypoplastic A1 segment of the left anterior cerebral artery.

Both posterior communicating arteries are hypoplastic.

Otherwise, the circle of Willis appears unremarkable.

Annotated image

Hypoplastic A1 segment of the left anterior cerebral artery (yellow arrow).
Both posterior communicating arteries are hypoplastic.
Otherwise, the circle of Willis appears unremarkable.

Case Discussion

Anterior cerebral artery A1 segment hypoplasia is an uncommon fetal variant of the circle of Willis. The frequency of this congenital variation is 1–13% as derived from angiograms and autopsy reports 1.

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