Aneurysm of a persistent primitive olfactory artery. Case report.

A ruptured anterior cerebral artery (ACA) aneurysm is reported in a patient in whom an anomalous ACA arose from the internal carotid artery at the bifurcation. The aberrant artery coursed anteriorly along the ipsilateral olfactory tract and made a hairpin turn posterior to the olfactory bulb, supplying the circulation of the ACA. Persistence of the primitive olfactory artery is suggested as an embryological origin of this vascular anomaly.