Effects of medication and deep brain stimulation on speed and amplitude are different between finger and forearm in patient with parkinson's disease

Although differential effects of medication and deep brain stimulation (DBS) on bradykinesia have been addressed in the literature, speed and amplitude have not been separated. This study investigated the differential effects of medication and DBS on quantitative measures of speed and amplitude, as well as on proximal and distal muscles of upper extremities. Fourteen upper limbs affected by Parkinson's disease were tested. Finger tapping and forearm rotation were performed to investigate distal and proximal bradykinesia, respectively. Test conditions included off-treatment, DBS only, medication only, and medication + DBS. Quantitative outcome measures included root-mean-square average of speed and amplitude. Two-way and one-way ANOVA (analysis of variance) were performed to investigate the effects of medication and DBS, and to compare the performance in four test conditions, respectively. Speed was improved at both body parts, whereas amplitude was improved only at the proximal forearm (p < 0.01). Medication tended to be better than DBS at distal speed, whereas DBS tended to be better than medication at proximal amplitude. Medication + DBS resulted in the best average performance in all outcome measures. Improvement in speed and amplitude in each body parts are differentially associated with medication and DBS. Medication and DBS have complementary effects in amelioration of bradykinesia. The findings may be helpful for clinical interventions and evaluations.