(5) An Implanted Modular Neuroprosthesis Providing Motor Function for Individuals with Spinal Cord Injury

Introduction: Our goal is to provide individuals who have a cervical level spinal cord injury (SCI) with improved motor function to enable them to be more independent in daily activities. To achieve this goal, we have developed a modular implanted neuroprosthetic system that utilizes electrical stimulation to activate the paralyzed muscles throughout the body. Control of the stimulation is given to each user via myoelectric signals generated from their voluntary musculature, which is supplemented with a smartphone interface.

Methods: We have developed an implantable network of modules, the “networked neuroprosthesis” (NNP), which is capable of stimulating paralyzed muscles throughout the body and recording myoelectric signals from muscles under voluntary control. Coordinated stimulation patterns can be programmed into the NNP to create functional movements on command. Using this system, we can provide motor complete cervical SCI individuals with grasp opening and closing, and, in some cases, overhead reach and trunk stability. The NNP system is implanted in a one- or two-stage surgical procedure. The outcome measures of this prospective, non-randomized, multi-methods single-arm trial include measures of grasp strength and ability, performance in activities of daily living, and qualitative interviews.

Results: Implantation of the NNP System has occurred in nine individuals with cervical SCI to date. The maximum period of follow-up now exceeds seven years. The results show that individuals with cervical SCI can learn to control hand grasp and other stimulated movements using the combination of myoelectric control and switch controls. Recipients of the implanted NNP System can perform many different activities of daily living more independently than when the system is turned off. The implanted system has proven to be extremely reliable in most aspects, particularly with respect to the reliability and longevity of the implanted stimulating and recording electrodes. Powering and communication within a modular system such as the NNP have been adequate for daily function but have required an upgrade to the technology to extend longevity of the system beyond two years.

Conclusion: The NNP is the first modular neuroprosthesis designed to provide multiple coordinated functions for individuals with SCI. This system provides increased functional ability of the hand and arm. The system is fully implanted (no external components), freeing the user in their activities. The results show maximum benefit is gained when using a neuroprosthesis when compared to existing alternative approaches to provide grasp function.