Primary degeneration of the granular layer of the cerebellum (Norman type). A Golgi study.

Purkinje cells, impregnated with the rapid Golgi method, in a patient with primary degeneration of the granular layer showed abnormal orientation of the perikaryon and dendrites, reduction in size of the dendritic arbor, absence of spiny branchlets, and large numbers of stubby spines and hypertrophic spines on secondary dendritic branches; stubby spines and thorn-like formations were seldom observed on the primary dendrites and perikaryon of some Purkinje cells. These findings are similar to those described in the cerebellum of the homozygous weaver mutant mouse and in the cerebella of experimentally induced agranular phenocopies, thus suggesting that similar plastic changes occur in human and animal Purkinje cells as a result of the absence of parallel fibres input in early developmental stages. In addition, Purkinje cells in this patient showed club-shaped deformities in the distal region of primary dendrites, which were filled with radially oriented, short dendrites covered with stubby spines and hypertrophic spines. These latter structures appear to be fully impregnated asteroid bodies observed in paraffin sections.