Cortical dysplasia in a 23-week fetus with Fukuyama congenital muscular dystrophy (FCMD).

A 23-week fetus who is thought to be affected with Fukuyama congenital muscular dystrophy (FCMD) is reported. Cortical dysplasia of the cerebrum was extensive and could be categorized into three major types. The cerebral cortex was thoroughly covered by glio-mesenchymal tissue (extracortical glial layer), in which neuronal clusters were irregularly scattered. Radial bundles of neuroglial tissue frequently extended from the cortex into the extra-cortical glial layer through the focally defective molecular layer and pia mater. The deep cerebral structures, such as basal ganglia, thalamus and white matter, appeared normal in contrast with extensive malformation in the cortex. Glial fibrillary acidic protein-immunoperoxidase stain revealed: (1) presence of abundant radial glial fibers in the ventricular, subventricular and intermediate zones; (2) focal or diffuse lack of glia limitans; (3) focal derangement of radial glial fibers; and (4) proliferation of stellate glial cells in the extra-cortical layer. It is suggested that ectopic accumulation of neurons into the extra-cortical glial layer seems a cardinal pathogenetic process to generate cortical dysplasia in FCMD. Early development of superficial glio-mesenchymal tissue seems essential for upward displacement of migrating neurons.