Paralytic rabies: a clinico-pathological study

Abstract

Clinical and pathological features of 11 cases of paralytic rabies have been described, with a detailed study of the peripheral nerves. The mean incubation period was forty-nine days (range 7-90 days). The mean interval between the onset of symptoms and death was 8.4 days (range 7-11 days). A history of animal bite was available in 9 cases. Pain and paraesthesiae at the site of the bite, followed by paralysis, were the main presenting symptoms. Motor weakness and involvement of the respiratory muscles was present in all cases. Histopathological features in the spinal cord and brain were (i) an inflammatory cellular reaction, (ii) vascular changes and (iii) inclusion bodies. Pathological changes were more severe in the spinal cord and brain-stem than in the cerebral cortex. Peripheral nerves showed segmental demyelination and remyelination. Wallerian degeneration, myelinated fibre loss and axonal loss. The changes were of variable degree. In 9 nerves segmental demyelination was the primary lesion. Wallerian degeneration and segmental demyelination were seen in 6 peripheral nerves. All the spinal nerves showed evidence of Wallerian degeneration as well as segmental demyelination. It is suggested that some protein component of rabies virus may produce primary demyelination in peripheral nerves by a cross-antigenic action on myelin protein, but that the pathological features in the spinal cord and brain are due to virus infection per se.