P040 Restoration of abnormal muscular cramping in musicians’ dystonia through bihemispheric transcranial direct current stimulation and bimanual motor retraining

Abstract

Question Task-specific focal dystonia (TSFD) is typically characterized by involuntary and abnormal muscular cramping, which compromises fine motor control. Previous neurophysiological studies have identified loss of inhibitory control at the motor cortex as a possible pathophysiology of the dystonic cramping. A recent study demonstrated that bi-hemispheric transcranial direct current stimulation (tDCS) over the motor cortices during performing bimanual mirrored finger movements ameliorated impairment of dexterous finger movements in pianists with TSFD. However, little has been uncovered about its underlying neurophysiological mechanism. Here we tested a hypothesis that the bi-hemispheric tDCS with motor retraining normalizes abnormal co-contraction between antagonistic pairs of extrinsic finger muscles in pianists with TSFD. Methods Eight pianists suffering from TSFD at the right hand and eight healthy pianists performed the bimanual mirrored finger movements for twenty-four minutes with two conditions; either with 2 mA tDCS over the motor cortices (cathodal over the left and anodal over the right) for twenty-four minutes (real condition) or thirty seconds (sham condition). Results The results demonstrated changes in pattern of muscular co-contraction only following the real stimulation condition, in which tonic activity turned into more phasic pattern. In addition, the amount of muscular co-contraction was significantly decreased after the real stimulation in the patients, which was the case neither at the sham condition of the patients nor at both conditions of the healthy controls. Conclusions The results provide physiological evidences of restoration of both abnormal pattern and amount of muscular co-activation of musicians’ dystonia through the bi-hemispheric tDCS with bimanual motor retraining.