Viliuisk encephalomyelitis (VE) is an unique neurological disease occurring in 
the Iakut (Sakha) people of Siberia. Evolution of the disease follows one of 
three broad clinical forms: subacute, slowly progressive or chronic. Death 
occurs within 3 to 6 months in subacute cases and within 6 years in the slowly 
progressive cases. Chronic cases lack a subacute phase but show a slowly 
progressive dementia associated with bradykinesia, dysarthria and spastic 
paraparesis that stabilizes late in the disease process. In subacute and slowly 
progressive cases, focal necrotizing encephalomyelitis is seen at necropsy. 
Chronic cases show multifocal areas of lysis with a gliotic margin, 
predominantly within grey matter, lacking associated chronic inflammatory 
changes seen in the other forms of the disease. Epidemiological studies are 
consistent with a disease of low-grade communicability, but laboratory studies 
have so far failed to reveal an infectious organism. The spectrum of 
neuropathological changes are reviewed in this examination of 11 cases. Although 
the aetiology of VE remains obscure, further studies are warranted since it may 
represent a novel disease process.