True fenestration of an extremely long anterior communicating artery diagnosed by magnetic resonance angiography

Purpose To describe a case of true fenestration of an extremely long anterior communicating artery (ACoA). Methods A 3-year-old boy with a history of a ventricular septal defect and aortic coarctation underwent magnetic resonance (MR) imaging and MR angiography of the head and neck regions using a 3-Tesla scanner. Results MR angiography of the head region showed an extremely long ACoA of approximately 20 mm in length, with a fenestration of approximately 5 mm in size. No aneurysms were observed. Conclusion According to a meta-analysis, the mean length of the ACoA was 2.84 mm (0.38–10.4 mm). The ACoA has been reported to be the most frequent site of fenestration of intracranial arteries. However, most reported ACoA fenestrations are not true fenestrations, but duplications or partial duplications. We herein report a case of true fenestration of an extremely long ACoA, which is an extremely rare variant. To our knowledge, this is the first report of such an association in the relevant English language literature.