A rare combination of anterior cerebral arterial ring with accessory middle and duplicated posterior cerebral arteries.

PURPOSES: To report a unique configuration of the cerebral arterial circle identified incidentally during magnetic resonance angiography (MRA). METHODS: An 87-year-old female patient was evaluated using MRA on a 3-Tesla scanner with the time-of-flight (TOF) technique. RESULTS: On the anterior circulation, an arterial ring was identified at the junction of the left anterior cerebral and anterior communicating arteries, suggesting a double origin of the left A2 segment. An accessory middle cerebral artery originated from the proximal left A1 segment. Additionally, the right A1 segment was aplastic, with the right A2 segment supplied by the left anterior cerebral. In the posterior circulation, the left posterior cerebral artery exhibited a fetal-type origin with a hypoplastic P1 segment. On the right side, a duplicated posterior cerebral artery originated from the internal carotid artery and supplied the temporal branch. CONCLUSIONS: This case presents a rare combination of an A2 double origin, accessory MCA, and PCA duplication, highlighting the morphological complexity of the cerebral arterial circle. Detailed preoperative assessment using volume-rendered MRA is essential to identify such complex variants and minimize intraoperative complications.