Bilateral anterior cerebral artery-anterior communicating artery junction arterial ring associated with unilateral A1 aplasia diagnosed by magnetic resonance angiography

Abstract Purpose To describe a case of two arterial rings of the anterior cerebral artery (ACA)-anterior communicating artery (ACoA) complex diagnosed by magnetic resonance angiography (MRA). Methods A 72-year-old woman with a brain tumor underwent cranial magnetic resonance imaging (MRI) and MRA using a 3-Tesla scanner. MRA was performed using a standard 3-dimensional time-of-flight technique. Results MRI showed a small convexity meningioma in the right parietal region. MRA showed no pathological lesions. The A1 segment of the left ACA was absent and the bilateral A2 segments were supplied by the right ACA. Two arterial rings were present bilaterally at the ACA-ACoA junction. The arterial rings showed a triangular configuration, suggesting a duplicate origin of A2 rather than A2 origin fenestration or partial duplication of the ACoA. A fetal-type right posterior cerebral artery was also observed. Conclusion The ACA-ACoA complex is the most frequent site of cerebral arterial fenestration. However, ACoA duplication, partial ACoA duplication, and other arterial rings of the ACA-ACoA complex have been confused and reported as ACoA fenestration. True fenestration of the ACoA is rarely been reported. The present case had bilateral ACA-ACoA junction triangular rings, suggesting a bilateral duplicate origin of the A2 segment of the ACAs. No similar case has been reported in relevant English-language literature. Careful observation using MRA is important for the detection of rare arterial variations. Partial volume-rendering MRA images are useful for identifying complicated small arterial variations.