Master Theses UMCG - University of Groningen
English | Nederlands

The effect of Deep Brain Stimulation on Corticomuscular Coherence in Parkinson's Disease

(2017) Dijks, J.G.

Background: In advanced Parkinson’s disease (PD), deep brain stimulation (DBS) is considered as an ultimate treatment; however inefficacy and side-effects remain a challenge. A reliable, non-invasive neurophysiological biomarker could be valuable enabling the application of DBS in a highly selective way. Corticomuscular coherence (CMC) could be used as a potential biomarker. CMC is seen as a representation of the co-operation between brain areas and muscles in motor tasks and is present in PD symptoms of tremor (tremor frequency range) and akinesia-rigidity (beta range).
Aim: To test CMC, measured by electroencephalography (cortex) and electromyography (muscles), as a potential biomarker for improvement in tremor and akinesia-rigidity after DBS.
Methods: In this single center prospective cohort pilot study, five tremor-dominant and five akinetic-rigid PD DBS candidates of the University Medical Centre Groningen (UMCG) were included. In the akinetic-rigid PD group, beta CMC was measured during a flexion, pinching and resting task; symptoms were assessed by the MDS-UPDRS III upper body akinetic-rigid items. In the tremor-dominant PD group, tremor CMC was retrieved during a maximal tremor task; symptoms by use of a clinical tremor score and accelerometer. Change in CMC after DBS was tested and correlations were performed between CMC and symptom severity. Thereafter, correlations between change in CMC and improvement in symptoms; and pre-DBS CMC and improvement in symptoms were made.
Results: Tremor CMC decreased significantly after DBS (p=0.01) and significantly correlated with tremor severity (p<0.01). No relation between the decrease in tremor CMC and tremor reduction; and between pre-DBS CMC and tremor reduction was found. No significant increase in akinetic-rigid PD total beta CMC was detected after DBS and no relation with severity and improvement in akinesia-rigidity was seen. However, high beta CMC during flexion did correlate with severity (rs =-0.45; p<0.05), and improvement in akinesia-rigidity correlated with the percentage increase in high beta CMC and high beta CMC pre-DBS (rs =0.75, p=0.01; rs =-0.71, p=0.02).
Conclusion: Correlations between high beta CMC with symptom severity and clinical effect during flexion in the akinetic-rigid PD group were found; in the tremor-dominant PD group, CMC did decrease significantly and was associated with symptom severity. However, the beta CMC was insignificantly increased after DBS in the akinetic-rigid PD group and there were lack of correlations between tremor CMC and clinical effect in the tremor-dominant PD group. Further, due to the small sample size in this pilot study, utility of CMC as a potential biomarker cannot be recommended yet and further research on a larger scale is strongly advised.

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