[New data on the epidemiology and morphology of Viliuisk encephalomyelitis].

Viliuisk encephalomyelitis (VEM) appears to be endemic disease, affecting native population in Yakutia (Yakut, Even, Evenk). The infectious nature of VEM is very likely, but not yet established with certainty. The mortality rate caused by VEM from 1950 to 1990 was 17.4 per 10000 of native population. The maximum morbidity can be seen in Viliui and Central zones of Yakutia. Women were affected one and a half times more than men. VEM is characterized by multiple micronecrotic foci with marked inflammatory reactions and gliosis in the brain tissue. The vascular component in VEM is manifested by vasculitis, plasmarhagies, obliteration of the capillary lumen with development of capillarofibrosis, progressive reduction of the microcirculatory bed, the deformation of walls in major vessels with atrophy of their muscular layer, in some cases--by hyaline thrombi. The data presented give no grounds to consider the vascular component as secondary, relating only to the brain atrophy.