Described is a lethal course of tick-borne encephalomyeíitis (TBE) in a fifteen-year old boy. The illness had a very short history, one-phase course, rapid development of disturbed consciousness, flaccid quadruplegia and brain-stem symptomatology. Examination of the cerebrospinal fluid (CSF) revealed a protein-cytologi-cal association, however, the magnetic resonance (MR) finding in the brain rather indicated a toxic myeli-nolytic affection of the stem. The diagnosis has been confirmed by the ELISA test demonstrating antibodi-es against the TBE virus in the sérum and CSF. Besides differential diagnostics and treatment, discussed is the participation of other factors in the unfavorable course of the illness. Attention is brought to prevention through vaccination.

        Key words: tick-borne encephalitis - encephalomyeíitis - CSF - magnetic resonance - differential diagnos¬tics - therapy - prevention.