Quantitative assessment of deep brain stimulation on tremor in multiple sclerosis disease

Background and Purpose: Multiple sclerosis (MS) is a chronic disease that gives rise to anumber of unpleasant symptoms that can be difficult to manage by conventional means. There aresome aspects of MS-related disability which can be improved by using Deep Brain Stimulation(DBS); particularly movement disorders, such as tremor. The research aim is to study the effectof DBS on MS tremor with a quantitative approach.Methods: Raw tremor data was provided by the Surgical Center for Movement Disorders atthe University of British Columbia, Canada. The hand tremor signal was collected on 8 MSsubjects and 10 healthy individuals during finger-to-nose test (FNT) by using motion analysissystem. Patients executed the FNT with DBS OFF and ON. Nonlinear and statistical featureswere extracted from tremor spectrum as tremor indexes. Tremor reduction by using DBS wasdetermined by classifying mentioned features into three groups of healthy, DBS ON and DBSOFF.Results: Several dominant peaks were observed in power spectrum of the recorded signals whichindicate MS tremor consists of several tremor subtypes due to different sites of demyelinatinglesions affecting cerebellum and its output pathways. Results of frequency analysis revealedtremor spectrum dominant frequency in healthy group was significantly greater than for thepatients with DBS ON and OFF (p < 0.05). Additionally, classification results demonstrated thattremor of 6 patients out of 8 decreased significantly when their DBS was ON.Conclusion: Overall, in 75% of patients with MS who suffered from tremor, thalamic DBSsignificantly reduced their tremor. In addition, power spectrum dominant frequency has highpotential for a quantitative and objective measure of MS tremor