Azygos anterior cerebral artery

Case contributed by Dr Safwat Mohammad Almoghazy


A known case of gastric GIST. Postoperative decrease conscious level investigated with an urgent CT brain.

Patient Data

Age: 60 years
Gender: Female
Modality: CT

Incidentally noted small but present A1 segment of the left anterior cerebral artery. The left and right A1segments join to form a single trunk making an azygos anterior cerebral artery (rare normal variant), before branching into normal branches. 

No evidence of acute brain insult. 

Modality: Annotated image

Annotated images. 

Case Discussion

An azygos anterior cerebral artery is an uncommon-to-rare variant of the circle of Willis where the two A1 segments of the anterior cerebral artery (ACA) join to form a single trunk. As a result, there is no anterior communicating artery. This organisation is similar to that seen in lower primates.

The clinical importance of an azygos artery:

  • may be associated with a number of brain anomalies such as dysgenesis of corpus callosum and holoprosencephaly, and a predisposition to aneurysm formation
  • an occlusion of an azygos artery may result in infarcts of the bilateral medial frontal lobes and corpus callosum


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Case Information

rID: 51987
Case created: 16th Mar 2017
Last edited: 22nd Apr 2017
Inclusion in quiz mode: Excluded

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