Orbitofrontal artery arising from a hairpin turn in type 1 persistent primitive olfactory artery: a possible new variant (type 6)

Purpose To describe a case of a possible new variant of persistent primitive olfactory artery (PPOA). Case report A 93-year-old man with left hemiparesis and dysarthria underwent cranial magnetic resonance (MR) imaging and MR angiography using a 3-T scanner. MR imaging showed an acute infarction at the right precentral gyrus. MR angiography showed no steno-occlusive lesions, but the distal A1 segment of the left anterior cerebral artery (ACA) took an extreme anterior course and made a hairpin turn, connecting to the A2 segment, which is indicative of type 1 PPOA. In addition, there was a faintly visualized small artery arising from the hairpin turn. Subsequent computed tomography (CT) angiography showed that the hairpin turn had a mildly dilated arterial lumen, and an extremely tortuous orbitofrontal artery arose from the hairpin turn. Discussion There are five types of PPOA. Type 1 is most common, and usually no arterial branch arises from the hairpin turn, except for in type 3 PPOA, which has a branch continuing to the anterior ethmoidal artery arising from the hairpin turn. Using MR and CT angiography, we diagnosed a case of type 1 PPOA associated with the orbitofrontal artery arising from a hairpin turn. A similar previously reported case was diagnosed using catheter angiography. Conclusion The present case may be a new variant (type 6) of PPOA. Because the orbitofrontal artery was relatively small in caliber and its proximal segment extremely tortuous, CT angiography had superior utility to MR angiography for demonstrating this variation.