EEG findings in tick-borne encephalitis.

EEG findings of epidemiologically and serologically confirmed tick-borne encephalitis patients were compared with findings of patients having acute encephalitis of viral or undetermined origins. Tick-borne encephalitis patients had more bilaterally synchronous bursts of slow waves and more focal abnormalities than did controls. Moreover, their EEGs remained mildly pathological, with increased slow and beta activity and intermittent focal abnormalities in some patients, whereas, EEGs in the controls became normal or borderline, usually within two months. EEG can thus reveal differences between individuals' responses to encephalitis and between different types of encephalitis, even though the clinical pictures are rather similar. Finally, the study shows that tick-borne encephalitis causes changes in the EEG that persist long after the clinical disease appears to have resolved.