Structural organization of the cerebral cortex (motor area) in human chromosomal aberrations. A golgi study. I. D 1 (13–15) trisomy, patau syndrome

Abstract

The fibrillar-neuronal organization of the cerebral motor cortex (area 4) of a newborn girl with 13–15 trisomy (Patau syndrome) has been studied, for the first time, utilizing both hematoxylin and eosin and rapid Golgi preparations. A variety of structural abnormalities considered to be sufficient to explain and possibly capable of causing some degree of cortical dysfunction have been found in the motor cortex of this infant. The significance of these findings becomes obvious in view of the fact that mental retardation is a prominent feature of infants with this chromosomal defect who survive to an age in which neuronal dysfunction can be reasonably judged. The motor cortex of this infant is characterized by a generalized hypocellularity which includes both a reduction in the number of neurons and glial cells. The possibility that the primordial cortical plate in this chromosomal defect may be primarily hypocellular is suggested. Cortical neurogenesis, neuronal migration, formation of the different cortical layers and development of the different neuronal types and systems of afferent fibers are considered to evolve normally in this chromosomal disorder. The neurons of the motor cortex of this infant depict a mild degree of delayed structural and functional maturation. The number of spines (postsynaptic components of the axo-spinodendritic synapses) is reduced and their distribution along the apical dendrite of the layer V pyramidal neurons is abnormal. The apical dendrite of these neurons received an inadequate amount of information along the dendritic segments which cross the cortical territories of layers III and II. In view of these findings, it is postulated that poor motor coordination and possible inadequate intercortical association should be prominent features in the type of mental retardation encountered in this chromosomal disorder. In addition, the dendritic spines depict structural abnormalities considered also to be capable of causing functional inadequacy of the axospinodendritic synapses. This study demonstrates that abnormal structure (spine anomalies) may be directly related to abnormal function (mental retardation). Also, it demonstrates and emphasizes the need to study further the fibrillar-neuronal organization of the cerebral cortex of infants with any type of mental retardation including those infants with the so-called minimal brain damage (MBD) with specialized neurohistological techniques ( e.g., rapid Golgi method) in addition to the routine methods.