This time-of-flight MR angiogram shows 3 A2 segments of the anterior cerebral arteries. The central (anomalous) one arises from the anterior communicating artery, and is known as a median artery of the corpus callosum. This anomaly occurs in 3% of the population. As with other ACA anomalies, there is an increased incidence of cerebral aneurysm.
Other ACA anomalies include unilateral hypoplastic A1 segment (6%), azygous (unpaired) A2 (2%), fenestrations (1%) and asymmetric A2 segments (bihemispheric A2). The incidence of ACA aneurysms in patients with unilateral hypoplastic A1 is around 14%, and is thought to be due to altered haemodynamic stresses at the A1/A2/ACOM junction.
Reference: Uchino A, et al. Anterior cerebral artery variations detected by MR angiography. Neuroradiology 2006;48:647-652
Credit: Dr Laughlin Dawes