Combined rare anatomic variants: persistent primitive olfactory artery and azygos pericallosal artery

The persisting primitive olfactory artery (PPOA) is a rare anatomic variation of the anterior cerebral artery (ACA), being encountered in less than 1% of cases. Different morphological types were reported previously. In type 3, only once reported previously, the PPOA gives off two branches, a nasal one which courses in the olfactory sulcus to supply the territory of the anterior ethmoidal artery, and the callosomarginal artery. It is reported here a combination of rare anatomic variants found in a 71-year-old male patient investigated by computed tomography angiography. A left PPOA left the A1 segment of the ACA and was classified as subtype 3b, as its branches were the nasal one and a frontal trunk, not the callosomarginal artery. That PPOA had a characteristic hairpin turn applied on the anterior fossa floor. The ACA continued as azygos pericallosal artery, which is also a rare finding. As the nasal branch of the PPOA and its hairpin turn is closely related to the anterior fossa floor, such variant should be carefully documented when combined approaches of the skull base are planned by rhinologists and neurosurgeons.