Azygos anterior cerebral artery

ALL are TRUE about Azygos anterior cerebral artery EXCEPT

[A] Single A1 segment of the anterior cerebral arteries
[B] Single A2 segment of the anterior cerebral arteries
[C] Ascending through the interhemispheric fissure
[D] Associated with formation of Saccular Aneurysms

ANSWER

[A] Single A1 segment of the anterior cerebral arteries

The Azygos anterior cerebral artery is a rare variant, characterized by the absence of the anterior communicating artery and the union of the two proximal segments (A1) of the anterior cerebral arteries, forming a single stem (A2)

Why Azygos anterior cerebral artery is Associated with formation of Saccular Aneurysms?

In patients with an azygos ACA, aneurysms of a distal segment of ACA occur relatively frequently.
The aneurismal development may be due to burden of blood from the bilateral A1 segment prior to
anomaly of A2 segment.

Incrreased flow from Both A1 segment to Single Azygous A2 may cause Saccular Aneurysm

Conventional Anatomy

Normal variant – anterior cerebral artery Presence of Anterior communicating artery. Presence of A1 & A2 Segment bilaterally

Azygous Anatomy

Azygos anterior cerebral artery Absence of the anterior communicating artery and the union of two proximal segments of the anterior cerebral artery, forming a single trunk