Large arterial ring formed by a duplicate origin of the middle cerebral artery (MCA) with a frontal branch arising from the superior channel of the ring (main MCA) diagnosed by magnetic resonance angiography

PurposeTo describe a case of large arterial ring formed by a duplicate origin of the right middle cerebral artery (MCA) associated with a frontal branch arising from the superior channel of the ring (main MCA) using magnetic resonance (MR) angiography.MethodsAn 81-year-old man with spinocerebellar degeneration underwent cranial MR imaging and MR angiography using a 1.5-Tesla scanner. MR angiography was performed using a standard 3-dimensional time-of-flight technique.ResultsMR imaging showed cerebellar atrophy and multiple cerebral white matter lesions. Regarding family history, he was diagnosed with Machado-Joseph disease. On MR angiography, an anomalous artery arose from the lateral wall of the supraclinoid segment of the right internal carotid artery (ICA) and fused with the main MCA, forming a large arterial ring. Thus, the anomalous artery was diagnosed as a duplicate origin of the MCA and not a duplicated MCA. The frontal branch of the MCA arose from the superior channel of the arterial ring (main MCA).ConclusionThis variation is called "segmental duplication of the MCA." However, this term may be confused with a duplicate origin or fenestration of the proximal M1 segment of the MCA. We report the first case of this combined variation diagnosed using MR angiography.