An electron microscopic study of degenerative changes in the cat cerebellum after intrinsic and extrinsic lesions.

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AbstractDegenerative changes in the cerebellum of the cat have been observed electron microscopically 2 to 30 days after surgical lesions were placed in the inferior or middle cerebellar peduncles or after undercutting or isolating cerebellar folia. The changes were confined to the mossy fibers of the white matter and granular layer except when Purkinje cells were damaged buy undercutting. Mossy fiber terminals in the glomeruli underwent two kinds of change. Either the synaptic vesicles and mitochondria coalesced into dense clumps with loss of mitochondrial outer membranes and proliferation of cristae, or the vesicles and miotochondria disappeared leaving a swollen terminal containing only a few large pleomorphic vesicles and small dense polygonal bodies. Neurofilaments proliferated and filled a few terminals but most of the neurofilamentous hypertrophy and proliferation was confined to myelinated axons. Some phagocytosis of degenerated endings was observed and mild fibrous gliosis occurred in the glomeruli.All of the changes observed in the present study have been reported in degenerating synapses and axons elsewhere in the central and peripheral nervous system, but there appeared to be more pleomorphism and less predictability of changes in the cerebellar cortex than have been noted in other single areas of the central nervous system.