Intraoperative Quantitative Measurements for Bradykinesia Evaluation during Deep Brain Stimulation Surgery Using Leap Motion Controller: A Pilot Study

Abstract

Deep brain stimulation (DBS) has shown a remarkably high effectiveness for Parkinson's disease (PD). In many PD patients during DBS surgery, the therapeutic effects of the stimulation test are estimated by assessing changes in bradykinesia as the stimulation voltage is increased. In this study, we evaluated the potential of the leap motion controller (LMC) to quantify the motor component of bradykinesia in PD during DBS surgery, as this could make the intraoperative assessment of bradykinesia more accurate. Seven participants with idiopathic PD receiving chronic bilateral subthalamic nucleus deep brain stimulation (DBS) therapy were recruited. The motor tasks of finger tapping (FT), hand opening and closing (OC), and hand pronation and supination (PS) were selected pre- and intraoperatively in accordance with the Movement Disorder Society revision of the Unified Parkinson's Disease Rating Scale. During the test, participants performed these tasks in sequence while being simultaneously monitored by the LMC and two professional clinicians. Key kinematic parameters differed between the preoperative and intraoperative conditions. We suggest that the average velocity ( $\overline{V}$ ) and average amplitude ( $\overline{A}$ ) of PS isolate the bradykinetic feature from that movement to provide a measure of the intraoperative state of the motor system. The LMC achieved promising results in evaluating PD patients' hand and finger bradykinesia during DBS surgery.

Figure 1

The software provides the real-time hand model and the trajectory of the movements to visualize the assessment process (a, b). Time-series kinematics extracted from the LMC for quantifying hand exercises included (c) FT: distance (mm) between distal joints of the thumb and index finger; (d) OC: average distance (mm) between the distal joints of the four fingers (except thumb) and the center of the palm; and (e) PS: roll angle (°) of the palm gesture which describes the rotational motion around the y-axis of the palm plane.

Figure 2

Representative segment of the kinematic signal reconstructed from (a) FT, (b) OC, and (c) PS. The black curve represents the 5 Hz low-pass filtered signal, the yellow dot represents the maximum value, and the blue dot represents the minimum value.