Aberrant morphogenesis of the central nervous system.
 This overview of congenital defects of the CNS has emphasized pathogenesis.
 As developmental pathways continue to be elucidated, this approach remains to an extent hypothetical.
 When, however, an understanding of the features of morphogenesis and dysmorphogenesis helps to indicate time of onset or to elucidate causal factors, important steps toward the prevention of birth defects are taken.
