Two-headed, two-necked conjoined twin calf with Arnold-Chiari malformation in a Japanese shorthorn calf.

A dicephalic Arnold-Chiari malformation (ACM) case revealed asymmetrical cranial bone abnormalities: the right cranium had the typical findings associated with bovine monocephalic ACM cases, whereas the left cranium had malformation that has not yet been described in previous bovine ACM cases. The only common finding in each cranium was a relative smallness of the cranium as the encasement of the brain.