Effect of Epidural Stimulation on Muscle Activation and Sensory Perception

"Step 1: Recording and stimulation of spinal potentials during insertion of epidural spinal stimulator paddle~Once the epidural paddle is placed, study procedures will begin by connecting the terminals of the paddle to an electrophysiological recording device for signal amplification and filtering. Using this recording setup, motor evoked potential (MEP) and somatosensory evoked potential (SSEP) protocols will be performed to determine motor and sensory thresholds, respectively. Next, the surgical procedure will resume and after the implantable pulse generator (IPG) has been placed, study procedures will begin again and include activation of both low-frequency tonic stimulation (LFTS) and high-frequency burst stimulation (HFBS) patterns from the inserted paddle while recording EMG signals."

"Step 3: Proprioception testing~The research team will investigate the perceived change in knee joint angle and direction of movement reported by the subject in a Threshold to Detect Passive Movement (TTDPM). The TTDPM protocol will begin with the subject sitting in the Biodex testing seat, with the non-tested leg hanging freely and the tested leg strapped to the rotating arm of the dynamometer at the lower shank. The subject will be blinded as to the mode and intensity of stimulation: HFBS, LFTS, or no stim. The TTDPM will consist of at least 10 trials for each stimulation condition chosen based on SCM outcomes. The subject has control of a kill-switch that immediately halts movement of the rotating arm, which is to be activated once the subject perceives movement OR if the subject begins to feel any pain or discomfort throughout the task."

"Step 4: Body weight support and treadmill (BWST) testing~Similar to step 2, LFTS and HFBS patterns will be compared by systematically testing each individual contact on the paddle while investigating for changes in stepping speed, pattern and EMG moduling complexity. Regarding EMG module analysis, muscle activity will be recorded bilaterally via surface EMG from lower extremity musculature. Furthermore, subjects will also have active LED markers placed over their clothes in order to track whole body kinematics throughout this portion of the study.~To optimize capture of steady state data on the treadmill, each subject will walk for approximately 10 sec prior to the 30 sec of data collection (40 sec per trial). This will allow capture of at least 10 consecutive steady state gait cycles (depending on cadence) per each amplitude selection for each stimulation delivery technique, which will be defined by parameters found during walking SCM."