ABSTRACT
In the ten years or so since the previous edition of this book was prepared there has been an extraordinary increase in our understanding of nervous system development. This particularly applies to animals, but it is already leading to a much better understanding of human brain development and its aberrations as well. Causative factors in human brain malformations include genetic traits, intoxications, hypoxia-ischemia, nutritional defects, maternal infections and irradiation. The time at which an insult acts on the developing brain is of particular importance in determining outcome, as malformations occur while a structure is in the process of developing. Later damage leads to destructive lesions (Chapter 19). In this chapter we shall confine ourselves to the description of some of the more common developmental anomalies. The conditions mentioned here are without doubt
heterogeneous; some are known to be of genetic origin while others are related to maternal nutrition (folate or vitamin A deficiency). Further information on these matters is to be found in Keeling (2001) and Harding and Copp (2002). As gross malformations can now be detected at an early stage of pregnancy and the fetus aborted, many fewer examples are seen postnatally.
