Viliuisk encephalomyelitis (VE) is an endemic neurological disease in 
Northeastern Siberia and generally believed to be a chronic encephalomyelitis of 
unknown origin. We investigated 17 patients with a clinical diagnosis of VE 
within the Viliuiski region of Sakha (Yakutian) Republic to explore the core 
clinical syndrome of chronic VE and subsequently whether VE is caused by 
Borrelia burgdorferi infection. We found a chronic myelopathy as the core of the 
syndrome, often following an acute phase with a meningo-radiculo-neuropathy, 
suggestive of chronic neuroborreliosis. A search for inflammatory parameters in 
a larger cohort in blood (39 VE patients and 41 controls) and CSF samples (10 VE 
patients and 7 controls) excluded an ongoing chronic infection, but revealed 
evidence for an immunological scar or a chronic inflammatory ("autoimmune") 
response in the CSF. In addition, we detected signs of a previous exposure to 
Borrelia burgdorferi antigens in a subset of chronic VE patients with positive 
serological results using ELISA/immunoblot in 54/10% and 22/0% of VE patients 
and controls, respectively (p values of 0.003/0.034; Fisher's exact test). 
However, CSF analyses did not show a link between exposure or at least 
immunological reaction against Borrelia and the risk of suffering from VE. Our 
data provide the first evidence of the presence of Borrelia burgdorferi or 
similar pathogens in Northeastern Siberia, but do not support a causative role 
of these pathogens in the aetiopathogenesis of VE.