Intermuscular coherence during co-contraction eliciting tasks as a biomarker for dystonia and GPi-DBS efficacy

•Intermuscular coherence of antagonistic muscles appears to be elevated in dystonic compared to non-dystonic arm muscles.•There is a notable decrease in intermuscular coherence of dystonic arm muscles one year after GPi-DBS treatment.•Intermuscular coherence of dystonic arm muscles might be of aid in the objective clinical assessment of dystonia patients. Clinical rating scales often fail to capture the full spectrum of dystonic symptoms. Deep brain stimulation of the globus pallidus interna (GPi-DBS) effectively treats dystonia, but response variability necessitates a reliable biomarker. Intermuscular coherence (4–12 Hz) has been linked to abnormal activity in the cortico-basal ganglia-thalamo-cortical (CBGTC) loop and may serve as an objective measure of dystonia and GPi-DBS effectiveness. A retrospective cohort study included 12 dystonia patients undergoing GPi-DBS implantation. Clinical rating scales and a neurophysiological assessment were performed before and one year post-DBS. Coherence in the 4–12 Hz range was analyzed from electromyography (EMG) of antagonistic arm muscles. Comparisons were made between patients with and without arm dystonia, t-tests evaluated the differences between pre- and post-DBS, and correlations between coherence and clinical scales were performed. Seven patients with arm dystonia appeared to have higher pre-operative intermuscular coherence compared to those without. Coherence was significantly decreased after GPi-DBS in the arm dystonia group. No strong correlations were found between coherence and clinical rating scales. Intermuscular coherence is present in dystonic muscles and decreases following GPi-DBS. Correlations with motor scores were inconclusive due to patient heterogeneity and ill-fitting clinical scales. Intermuscular coherence has potential to aid GPi-DBS patient selection and optimization but larger studies are needed to validate its use.