Pathological changes of the central nervous system in Encephalitis Japonica were studied in 53 autopsy cases collected during 1948-1951. Special attention was given to the pathogenesis of the glial nodules and the necrotic foci, and to the localization of these changes within the central nervous system. The results are as follows:
1. The most characteristic pathological picture noticed in the earliest stage of infection is the eosinophilic necrosis of nerve cells. This change is considered to result from the proliferation of the virus in these cells and not from circulatory disturbances.
2. Most of the glial nodules develop on the basis of neuronophagia. A few are localized on one side or around the blood vessels with no relationship to nerve cells. This latter change suggests a probable proliferation of Japanese encephalitis virus in the endothelial cells of the blood vessels and is supported by finding similar changes in other viscera.
3. Careful examination of minute nocrotic foci reveals a necrotic nerve cell in the center of these lesions. These minimal units of necrosis may coalesce and form the most commonly encountered military-sized necrotic foci.
4. Neuronophagia, glial nodules and necrosis which are the fundamental changes noticed in Japanese encephalitis are considered secondary to the necrosis of nerve cells. As these changes are characteristic for viral infections, it would seem possible that the development of these three changes are due chiefly to the proliferation of virus in the nerve cells, to its diffusion in the surrounding tissue and to its toxic action.
5. The degree of necrosis corresponds to the intensity of the primary infection, varying from focal areas of softening infiltrated by many scavenger cells, to cavernous formations, leaving behind many holes.
6. As these fundamental changes depend on the existence of nerve cells, almost no changes are seen in the white matter. Furthermore, the intensity of the secondary changes varies greatly in accordance with the degrees of damage to the nerve cells and the distribution of the lesions varies accordingly.
7. The selective involvement of certain nerve cells. cannot be explained by their morphological character alone, but it is considered possible that the internal composition of the nerve cells influences the proliferation of the virus.
I hereby wish to express my deep gratitude to Prof. Teisho Aoki for his cordial guidance.
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