Malformations of dorsal induction.

Dorsal induction includes the formation and closure of neural tube, occurs during 3-5 weeks of gestation. Neurulation occurs in two phases, primary neurulation (formation of the neural plate and subsequently neural tube) and secondary neurulation (formation of distal cord and sacral and coccygeal segments). Failure of dorsal induction leads to anencephaly, exencephaly, cephaloceles, Chiari malformation and spinal dysraphism. In this article we discuss the relevant embryology, etiopathology and detail imaging appearances of these malformations.