Objective: To define electrophysiological characteristics of tremor in patients with tick borne encephalitis (TBE).

Background: TBE is endemic in focal areas of Europe, including Slovenia. Besides typical symptoms for meningoencephalitis, around 40% of TBE patients present with action tremor of the upper limbs. Tremor is mostly transient, but it may persist in 15% of patients. Tremor in TBE has not been electrophysiologically defined and the mechanism of its generation remains unknown. Theoretically, it may represent enhanced physiological tremor, caused by the activation of sympathetic response in the febrile patient or may be due to the activation of central oscillators, triggered by meningoencephalitic process. Accelerometry with concurrent surface electromyography (EMG) may differentiate between enhanced physiological and central tremors. Eye-blink classical conditioning (EBCC) is a paradigm used to assess cerebellar function, which is known to be impaired in central tremors.

Method: We included 22 hospitalised patients (average age 42.2 years, 17 males) with confirmed TBE and new onset tremor. Severity of tremor was rated on TETRAS severity scale (0-4). Patients underwent EMG and accelerometry recordings (without and with 500 gr mass loading) and EBCC assessment. The results of EBCC were compared with group of 26 essential tremor (ET) patients. Head CT and/or MRI was performed in all TBE patients.

Results: Action  tremor was symmetric in 75% patients, while in 25 % it was clearly asymmetric or unilateral. 41% of patients manifested also tremor at rest. 41% had associated tremor of the tongue. The average TETAS severity score was 1.55 (±0.56). The average postural tremor frequency on the accelerometry, without and with weight loading, was 7.3 (±3.8) Hz and 7.6 (±2.6) Hz, respectively. All patients had corresponding frequency peak in the EMG. EBCC did not differ between patients with TBE and ET patients. The head CT and/or MRI was normal in all patients.

Conclusion: Our electrophysiological findings are consistent with central tremor generation in TBE. Unlike other pathologic central tremors, the TBE tremor is reversible and may be potentially used as a model of the vulnerability of the central oscillators.

« Back to 2022 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/electrophysiological-characteristics-of-tremor-in-patients-with-tick-borne-encephalitis/