A unique example of two fenestrations of the pre-communicating (A1) segment of the right anterior cerebral artery (ACA) in a 78-year-old woman was a special case among 388 cadaveric specimens. It was found by a retrospective review of the personal data obtained during graduate and undergraduate studies at the Faculty of Medicine. Two unequal fenestrations of the right A1 segment were associated with the presence of a pseudo anterior communicating artery, hypoplasia of the right posterior communicating artery and the left superior cerebellar artery, absence of the right anterior inferior cerebellar artery, and ectasia of the basilar artery; however, the cerebral arteries were without aneurysm(s) or other pathology. The reason could be the almost equal ACA diameter on both sides.
Keywords: anterior cerebral artery; associated arterial variations; brain base; fenestration.