The effect of 8 weeks of treatment with transcranial pulsed electromagnetic fields on hand tremor and inter-hand coherence in persons with Parkinson's disease

Abstract

Background: Parkinson's disease (PD) tremor comprises asymmetric rest and postural tremor with unilateral onset. Tremor intensity can be amplified by stress and reduced by attention, and the medical treatment is complex. Mirror movements and unintentional synchronization of bimanual movements, possibly caused by insufficient inhibition of inter-hemispheric crosstalk, have been reported in PD, indicating a lag of lateralization. Potential neuroprotective effects of pulsed electromagnetic fields (PEMF) have been reported in-vitro and in rodents, as have influences of PEMF on human tremor. The aim was to investigate the effect of 8 weeks daily transcranial PEMF treatment (T-PEMF) of persons with PD on rest and postural hand tremor characteristics and on inter-hand coherence.

Methods: Hand accelerations of 50 PD participants with uni- or bilateral tremor participating in a clinical trial were analysed. A rest and postural tremor task performed during serial subtraction was assessed before and after 8 weeks of T-PEMF (30 min/day, 50 Hz, ±50 V, 3 ms squared pulses) or placebo treatment (sham stimulation 30 min/day). Forty matched healthy persons (no treatment) were included as reference. Intensity and inter-hand coherence related measures were extracted.

Results: The T-PEMF treatment decreased the inter-hand coherence in the PD group with unilateral postural tremor. The PD group with unilateral postural tremor was less clinically affected by the disease than the PD group with bilateral postural tremor. However, no differences between T-PEMF and placebo treatment on either intensity related or coherence related measures were found when all persons with PD were included in the analyses. The peak power decreased and the tremor intensity tended to decrease in both treatment groups.

Conclusions: Eight weeks of T-PEMF treatment decreased inter-hand coherence in the PD group with unilateral postural tremor, while no effects of T-PEMF treatment were found for the entire PD group. The unilateral postural tremor group was less clinically affected than the bilateral postural tremor group, suggesting that early treatment initiation may be beneficial. In theory, a reduced inter-hand coherence could result from a neuronal treatment response increasing inter-hemispheric inhibition. However, this requires further studies to determine. Studies of even longer treatment periods would be of interest.

Trial registration: ClinicalTrials.gov , NCT02125032. Registered 29 April 2014, https://ichgcp.net/clinical-trials-registry/NCT02125032?term=NCT02125032&rank=1.

Keywords: Accelerometry; Inter-hand coherence; PEMF; Parkinson’s disease; Postural tremor; Rest tremor; T-PEMF; Tremor intensity.

Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the Regional Scientific Ethical Committees for Southern Denmark (S-20130114) and the Danish Health Authority (CIV-14-01-011780), and was conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to participation.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

Treatment effect on intensity related measures for the rest and postural condition, measured values. A and D Tremor intensity (TI). B and E Peak power (Powpeak). C and F Peak power (Freqpeak). T-PEMF = transcranial pulsed electromagnetic fields. REF = healthy reference group. * = significant difference from week 0 to week 8 across treatment groups (P ≤ 0.05). (*) = tendency of difference from week 0 to week 8 across treatment groups (0.05 < P ≤ 0.1). # = significant difference between the treatment groups combined at week 0 and REF (P ≤ 0.05)

Fig. 2

Treatment effect on inter-hand coherence measures for the rest and postural condition, measured values. A and D Coherence (Coh). B and E Peak coherence (Cohpeak). C and F Frequency of peak coherence (Cohfreq). T-PEMF = transcranial pulsed electromagnetic fields. REF = healthy reference group. * = significant difference from week 0 to week 8 across treatment groups (P ≤ 0.05). # = significant difference between the treatment groups combined at week 0 and REF (P ≤ 0.05). (#) = tendency of difference between the treatment groups combined at week 0 and REF (0.05 < P ≤ 0.1)