Generalized cortical dysplasia. Clinical and pathologic aspects.

Three children with profound mental retardation and intractable seizures died at ages 10 months, 3 years, and 7 years, respectively. Complete examination of their brains showed generalized cortical dysplasia, without any major malformation of the external gyral pattern. The neuropathologic features of cortical dysplasia include abnormally thickened cortex with indistinct demarcation of the gray-white matter junction. In many areas, the cortex contained increased numbers of large neurons with disordered cortical lamination. Heterotopic neurons were scattered throughout the white matter with decreased myelination of the underlying white matter. To our knowledge, these cases represent the first fully detailed neuropathologic study of diffuse cortical dysplasia--a newly recognized entity of abnormal neuronal migration.