Presentation
A known case of gastric GIST. Postoperative decrease conscious level investigated with an urgent CT brain.
Patient Data
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.
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 organization 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
occlusion of an azygos artery may result in infarcts of the bilateral medial frontal lobes and corpus callosum