Axonal degeneration and focal muscle fiber necrosis in human thallotoxicosis: Histopathological studies of nerve and muscle

Two cases of proven thallium poisoning were studied with special reference to the neuromuscular changes. These cases showed a consistent pattern of symptomatology of peripheral sensorimotor neuropathy, encephalopathy, and alopecia. Light and electron microscopic studies of the sural nerve biopsies exhibited mainly axonal degeneration without concomitant segmental demyelination. The densities of both large and small myelinated fibers were mildly decreased. Biopsied peroneus brevis muscles showed distinct features of focal muscle fiber necrosis which has not been reported before. Muscle fibers with prominent central nucleation and fiber splitting were frequently seen. These findings are compatible with myopathic changes. In spite of the existence of severe axonal degeneration and muscle atrophy on clinical observation, no neurogenic muscle changes were found.