Azygous Anterior Cerebral Artery

Findings:

A single A2 trunk supplies both parasagittal frontal lobes compatible with anatomic variant azygos ACA.

Discussion/Differential Diagnosis:

The azygous ACA A2 segment is an uncommon anatomic variant seen in less than 1% of the population. Embryologically, the ACA is the first to develop along the olfactory lobe, and was also the first cerebral artery to evolve in animal species with a telencephalon. It starts as a fenestrated weblike network over the primitive olfactory lobe and coalesces typically into two ascending A2 segments. Many variants of the ACA and ACOM exist, including a single A2 trunk supplying both hemispheres, duplicated or absent ACOM, and/or other smaller branch vessels arising directly from ACOM. Infraoptic origin of the ACA may also occur rarely. Abnormal flow states may lead to aneurysm development at branch points.

This case was prepared with the assistance of Joshua Hall, UC undergraduate

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