Focal cortical dysplasia is a localized disturbance of the cerebral cortex, with giant neurons and astrocytes and chaotic organization. This was recognized as an important cause of partial epilepsy (Taylor et al. 1971) and can now sometimes be recognized by MRI (Kuzniecky et al. 1988).
Focal cortical dysplasia
MRI, showing an area of focal cortical thickening with additional changes in the underlying white matter. Coronal fixed brain slice from the same patient, showing the area of thickened cortex. Note the associated poor definition of the cortical margin with groups of nerve cells which have not migrated normally. (Courtesy of Dr W. Squier.)
The cortical dysplasias comprise microdysgenesis (a purely microscopic abnormality), focal cortical dysplasia (as described above), macrogyria, polymicrogyria, pachygyria, and hemimegalencephaly.