Presenter: Sedona Cady
PI: Dr. Dustin Tyler
Title: Clinical Implementation of a High Channel Count, Bidirectional Somatosensory Neuroprosthetic System
Abstract: Percutaneous peripheral nerve stimulation using Flat Interface Nerve Electrodes (FINEs) and composite FINEs (C-FINEs) and myoelectric sensing using Tetra Intramuscular (TIM) electrodes can restore touch and relay motor intentions for upper extremity prosthesis users. However, the upkeep of the percutaneous leads, high wire count crossing the skin, and burden of using an external stimulator may deter prosthesis users from adopting the system at home. With this motivation, our team developed a high channel count implantable device with wireless communication for both stimulated somatosensation and myoelectric sensing: the implanted Somatosensory Electrical Neurostimulation and Sensing (iSens®) system. In this study, we characterize the chronic stability, evoked somatosensory percepts, and myoelectric performance of the iSens® system. Two participants with transradial amputations enrolled in the study and received the iSens® implant. Both participants’ iSens® systems include four 16-channel C-FINEs on the median, ulnar, and radial nerves and four TIMs in residual muscles, totaling 64 stimulating and 16 sensing channels. Cathode-first, charge balanced square pulse trains were applied at each contact to determine perceptual threshold charge across visits. Participants described sensation qualities and circled sensory locations on a tablet. EMG was recorded with and without stimulation to determine the extent of stimulation artifact in EMG. Non-increasing threshold charge values indicate that nerve health is preserved post-implantation. The iSens® system provides somatosensory percepts that almost completely cover the phantom hand. The stimulation artifact in EMG varies in magnitude depending on the recording channel, and therefore, ignoring high-noise myoelectric channels may be required to develop robust control algorithms.