Axonal and dendritic swellings on cerebellar Purkinje cells in a cow: a possible age-related change

Dystrophic or swollen axons occur in a variety of neurological disorders. Although the structures are often viewed as an incidental or age-related phenomenon, there are few reports that actually described axonal and dendritic swellings on cerebellar Purkinje cells in domestic animals with no apparent neurological clinical signs. A 12-year-old Holstein-Friesian dairy cow, which exhibited no apparent cerebellar or other significant clinical signs, was culled from old age. On histopathology of the cerebellum, there were Purkinje cell axonal torpedoes and axonal spheroids involving nerve fibers in the folial and medullary white matter, which were identified by Bodian’s silver impregnation technique and anti-neuron-specific enolase (NSE) immunohistochemical stain. Less frequently, dendritic swellings on Purkinje cells were found in the molecular layer. Cell bodies of Purkinje cells appeared otherwise normal and were not accompanied by Bergmann glia proliferation. Immunohistochemistry for glial fibrillary acid protein (GFAP) failed to demonstrate significant fibrillary gliosis. Deposition of lipofuscin pigments was seen in the cortical and medullary neurons and glial cells. Any sites of the cerebellum showed no evidence of neuronal cell degeneration, glial reaction, cellular infiltrates, or vascular lesions. Morphometrically, there was no significant decrease in number of Purkinje cells in comparison with younger control cows (n = 2). Purkinje cell axonal torpedoes or axonal spheroids were absent in the cerebellum of younger control cows (n = 10). The precise mechanism for the development of swollen Purkinje cell axons and dendrites remains to be determined, although an association with advanced age was considered one of the likeliest possibilities.