Aneurysm of the A1 Segment of the Anterior Cerebral Artery Associated with the Persistent Primitive Olfactory Artery.

Background: The persistent primitive artery constitutes the anterior cerebral artery proper. When the persistent primitive artery keeps its embryologic course along the olfactory bulb, it is called the persistent primitive olfactory artery (PPOA).

Case Description: A 69-year-old man presented with an incidentally discovered unruptured aneurysm at the origin of the PPOA. The PPOA originated at the A1 segment of the anterior cerebral artery, coursed anteromedially along the olfactory tract, made a hairpin turn posterosuperior to the midline, and formed the callosomarginal branch of the anterior cerebral artery. The anomalous artery was interpreted as a PPOA (type 3). Type 3 PPOA associated with an unruptured aneurysm is rare.

Conclusions: There is a high incidence of aneurysms associated with a PPOA. Follow-up studies are necessary in the present case to monitor for the development of another aneurysm at the hairpin bend.