Unilateral anterior cerebral artery (A1 segment) aplasia/hypoplasia

Case contributed by Amir Mahmud
Diagnosis certain


Patient was reported to have been behgaving strangely, hallucinating. As part of his work-up, a contrast enhanced CT head was performed.

Patient Data

Age: 25 years
Gender: Male

Contrast opacification of both the intracranial arterial and venous circulation may be appreciated.

There is non-visualization of the A1 segment (pre-communicating) of the right anterior cerebral artery. The left A1 is prominent and gives off the tortuous anterior communicating artery as well as both A2 (post-communicating) segments.

Case Discussion

Some degree of asymmetry is a well known normal anatomical variant of the anterior circulation of the intracranial arterial system. Aplasia or hypoplasia of the A1 (pre-communicating) segment of the anterior cerebral artery (ACA) accounts for about 10% of these variants.

Here, the contralateral A1 segment, as well as the anterior communicating artery (Acom), will be dilated and more prominent in order to adequately vascularize the entire area usually supplied by both anterior cerebral arteries.

There is an increased risk of ischemia in the frontal lobe region during intravascular procedures near the variant area or in the case of pathology involving ischemic episodes.

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