The morphogenesis of experimental malformations of the central nervous system in laboratory animals, if the malformations originated from abnormalities in the early developmental stage, will present useful information for understanding human cerebral malformations, since the brains during their organogenesis and early histogenesis are similar among different species of mammals.
The experimental malformations of the brain in the rat and mouse which are compatible with those in human are 1. organogenetic malformations: exencephaly, encephalocele, holoprosencephaly, 2. histogenetic malformations: microcephaly, dysgenetic hydrocephalus, absent corpuscallosum, heterotopic gray matter, disorganized cortical architecture.
The morphological states of the dysraphic malformations apt to be altered by sequential def ects of the skull bones and secondary degeneration of the brain tissue. The brains with histogenetic malformations are also easily involved in destructive changes due to abnormal vascularity, circulatory disturbance in the brain or failure of absorption of the cerebrospinal fluid, which occur as secondary changes of developmental abnormalities and growth retardation of the brain mantle. Consequently, the original maldevelopments fade out and are occasionally concealed by predominant destructive changes.
These findings in laboratory animals suggest that the developmental disorder of the brain in the early gestational period is probably one of the important causal factors of human cerebral lesions, which manifest themselves in the late gestational or perinatal period and cause cerebral palsies and mental deficiency after birth.
