Segmental duplication of the fetal anterior cerebral artery.

Segmental duplications (also termed 'fenestrations') of the fetal anterior cerebral artery are a relatively rare anomaly. Their occurrence was studied in 200 fetuses at 20-40 wk gestational age. Duplications were found in 21 of the 200 fetuses, i.e. 10.5%. In 2 fetuses, i.e. 1%, the duplications were bilateral. In 1 case, i.e. 0.5%, 2 duplications were found on the left anterior cerebral artery. There were 15 segmental duplications on the left anterior cerebral artery, i.e. 62.5% of all duplications, and 9 on the right, i.e. 37.5%. The duplications were located in the distal part of the A1 segment in 45.7%, at the level of the anterior communicating artery (A1-A2) in 37.7%, and in the initial part of the A2 segment in 16.6%. The duplications had 4 different forms namely oviform, fissured, triangular and punctate.