Brain defects in infants with Potter syndrome (oligohydramnios sequence)

Defects of neuronal migration were detected in the brains of five unrelated infants with Potter syndrome (oligohydramnios sequence). These consisted of abnormal lamination of cerebral cortex, white matter heterotopias, and meningeal and molecular zone neuronal-glial ectopias. Besides, various other brain anomalies were sometimes found. They comprised one or more of the followings: abnormal gyration patterns (gyral fusion, cerebellar microgyria), cerebellar granule and Purkinje cell heterotopias, brain stem heterotopias, adysplasia of basal ganglia, gliosis, mineralization, and hydrocephalus. Detailed investigations, using standard neuropathologic stains, immunohistochemical and Golgi methods, and a new electron microscopic histochemical technique that we applied to study the developing human brain, suggest that migration defects of neurons are caused by an abnormality in their glial guides, the radial glial fibers, during the period of cortical histogenesis. We hypothesize that abnormally and precociously induced radial glial transformation into astrocytes is the pathogenic mechanism for the defects in neuronal migration. The etiological factor(s) that precipitates such abnormal glial transformation seems to be heterogeneous. Its relation to the Potter anomaly is discussed.