Bilateral anterior cerebral artery-anterior communicating artery junction arterial ring (duplicate origin of the A2) associated with unilateral A1 aplasia diagnosed by magnetic resonance angiography.

PURPOSE

To describe a case of two arterial rings of the anterior cerebral artery (ACA)-the 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 at the right parietal region. MRA showed no pathological lesion. The A1 segment of the left ACA was absent, and bilateral A2 segments were supplied by right ACA. There were two arterial rings at the ACA-ACoA junction, bilaterally. The arterial rings showed triangle configuration, suggesting duplicate origin of the A2 rather than A2 origin fenestration or partial duplication of the ACoA. There was also fetal-type right posterior cerebral artery.

CONCLUSION

ACA-ACoA complex is reported to be the most frequent site of cerebral arterial fenestration. However, duplicated ACoA, partially duplicated ACoA and other arterial rings of the ACA-ACoA complex were confused and reported as a ACoA fenestration. ACoA true fenestration is rarely reported by MRA. The present case had bilateral ACA-ACoA junction triangular rings, suggesting bilateral duplicate origin of the A2 segment of the ACAs. No similar case has been reported previously in relevant English-language literature. Careful observation of MRA is important for the detection of rare arterial variations. Partial volume-rendering images of MRA is useful for identifying complicated small arterial variations.