Effect of deep brain stimulation frequency on gait symmetry, smoothness and variability using IMU

Deep brain stimulation (DBS) implant represents an appropriate treatment for motor symptoms typical of Parkinson's Disease (PD). However, little attention has been given to the effects of different DBS stimulation frequencies on gait outcomes. Accordingly, the aim of this pilot study was to evaluate the effects of two different DBS stimulation frequencies (60 and 130 Hz) on gait spatio-temporal parameters, symmetry, smoothness, and variability in PD patients. The analysis concentrated on acceleration signals acquired by a magnetic inertial measurement unit placed on the trunk of participants. Sessions of gait were registered for three PD patients, three young and three elderly healthy subjects. Gait outcomes revealed a connection with both age and pathology. Values of the Harmonic Ratio (HR) estimated for the three-axis acceleration signals showed subjective effects provoked by DBS stimulation frequencies. Consequently, HR turned out to be suitable for depicting gait characteristics, but also as a monitoring parameter for the subjective adaptation of DBS stimulation frequency. Concerning the Poincaré analysis of vertical acceleration signal, PD patients showed a greater dispersion of data compared to healthy subjects, but with negligible differences between the two stimulation frequencies. Overall, the presented analysis represented a starting point for the objective evaluation of gait performance and characteristics in PD patients with a DBS implant.