Rare Anatomic Variation of Anterior Communicating Artery Associated with a Rupture of Saccular Aneurysm

Although most cerebral aneurysms are considered as acquired degenerative lesions, diverse anatomical variations in the circle of Willis have been encountered, some of which may play an important role in lesion hemodynamics and pathogenesis. The coalescence of the small vascular plexus to form the anterior communicating artery at the 6-7-week embryological stage may lead to developmental variations, such as fenestration and duplication. Herein, we report a rare anatomical variant of the anterior communicating artery that was concomitantly identified with a ruptured aneurysm. Both the right and left anterior cerebral arteries were connected by three anterior communicating arteries. A vertical segmental artery was present and connected the two anterior communicating arteries, forming an H-shape or plexiform structure. Furthermore, a 0.6×0.4 cm-sized saccular aneurysm with antero-inferior projection was present in the middle anterior communicating artery. The combination of triplication and H-shape in the present case was compared to previously reported anatomical variants.