Neurulation and neural tube defects

Neurulation has been extensively studied in amphibian, avian and mammalian embryos and occurs in four stages: formation of the neural plate, shaping of the neural plate, bending of the neural plate and closure of the neural groove. The rostral part of the neural tube develops into the brain, whereas the caudal part becomes the spinal cord. This is the primary type of neurulation (Sect. 4.2). The most caudal part of the neural tube forms by aggregation of cells into a medullary cord which then cavitates and connects to the main neural tube. This process is called secondary neurulation (Sect. 4.3). Neural tube defects (NTDs) are among the most common of human malformations with an incidence of 1-5 per 1,000 live births. Genetic mouse models for NTDs are discussed in Sect. 4.4, the aetiology of human NTDs in Sect. 4.5 and prenatal diagnosis and fetal therapy in Sect. 4.6. Cranial neural tube defects (anencephaly, encephaloceles and cranial meningoceles) are discussed in Sect. 4.7 and illustrated in several Clinical cases. In Sect. 4.8, spinal neural tube defects are discussed and again illustrated in several Clinical cases, followed by the Chiari malformations (Sect. 4.9) and caudal dysgenesis (Sect. 4.10).