A quantitative study of the composition of cerebellar cortical dysplasias.

The areas of molecular and granular layers in four large cerebellar cortical dysplasias were measured with the planimeter and the Purkinje cells were counted. There was a relative deficit of molecular layer and a still greater deficit of Purkinje cells in three of the four dysplasias. The fourth one had normal numbers of Purkinje cells per molecular layer and a relative deficit of granular layer. These abnormal proportions in the composition of a dysplasia may relate to the timing of its origin.