Neurotoxicology of vincristine in the cat. Morphological study.

Vincristine is a vinca alkaloid widely utilized in cancer chemotherapy. Its major clinical limitation is due to a drug induced sensory-motor neuropathy, the pathogenesis of which is poorly understood. This communication describes the morphological basis of a vincristine neuropathy in cats. Major pathological lesions were focal axonal swellings (giant axon formations) due to malaligned accumulations of neurofilaments and secondary demyelination of the paranodal type. These were primarily confined to the proximal portions of the peripheral nerves. The distal portions of the peripheral nerves contained only a few giant axon formations. Wallerian degeneration was noted to involve a small number of nerve fibers in the distal regions.