This paper presents the development of a Dorsal Root Ganglion (DRG) stimulator system intended for use in early clinical trials for motor recovery after Spinal Cord Injury (SCI). It allows for independent control of multisite/multilevel bilateral (on both sides of the spinal cord) stimulation, it can supply a high output current of 25.4mA, and has the ability to program pulse sequences similar to actual locomotion patterns. These characteristics ultimately provide the required versatility for examining the effects of DRG stimulation on locomotion recovery, which is lacking in currently available commercial systems. The device is created using commercially available components to make the design reproducible by other research labs and to facilitate the critical approval procedure for use in a clinical research environment. Throughout the design phase, essential considerations regarding the safety of the participating patient, as well as of the medical personnel involved, were taken into account and these are analyzed and demonstrated in this paper. Such considerations are very rarely discussed in scientific literature and the authors consider that, apart from the design of the system itself, this discussion is a critical contribution of this paper.

Spinal Cord Injury (SCI) is characterized by a disruption of the spinal pathways connecting the brain to the rest of the body. This can result in an impairment or complete loss of sensory and/or motor functions, depending on the level and severity of the injury. The most common approach of attempting motor recovery using neuromodulation has been through epidural spinal cord electrical stimulation (eSCS), with or without rehabilitation and robotic assistance¹ , ². Dorsal Root Ganglion (DRG) stimulation is a relatively new neuromodulation treatment, which has already been established as a safe and effective treatment for chronic pain. However, its application for motor recovery after SCI has remained unexplored territory. A recent study by Soloukey et al.³ showed the first promising results using L4-level DRG-stimulation to evoke strong and reproducible motor responses in the upper leg muscles of patients with motor complete SCI. The current work presents the development of a prototype stimulator intended for use in early clinical trials for the purpose of further exploring the effects of multi-level DRG-stimulation on motor recovery after SCI. The prototype stimulator is created using commercially available components, focussing primarily on the safety considerations for the use of the prototype in a clinical research environment. The prototype allows for access to multiple leads in parallel to facilitate faster, sequential stimulation, catering for a maximum of 16 leads at once. The final system is equipped with a microcontroller for the programming of the stimulation parameters, a Bluetooth module for the communication with external components (Graphical User Interface (GUI) on a local PC) and tailored connections to the stimulating DRG-leads. The safety and well-being of the patient is set as a first priority, leading to a tailored design and development of the stimulator accordingly. Parameters like the patient's comfort when connected to the device, the safety of the patient and the medical personnel with regards to powering the device through the mains, and protection from any current or DC voltage leakage, are discussed. The prototype is currently undergoing safety evaluation and the complete system design together with these results will be presented during the conference.