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