OpenXstim: an open-source programmable electrical stimulator for transcutaneous spinal cord stimulation therapy

Objective.Transcutaneous spinal cord stimulation, a non-invasive spinal cord neuromodulation method holds tremendous promise and hope to restore functions in individuals with paralysis resulting from spinal cord injury (SCI), cerebral palsy, stroke and other neurological conditions. Yet, there are relatively few options for such stimulation devices compared to conventional stimulators commonly used for neuromuscular electrical stimulation, transcutaneous electrical nerve stimulation, and functional electrical stimulation, particularly for people with neurological conditions in the developing countries.Approach.In this report, we present OpenXstim, an open-source, two-channel programmable electrical stimulator developed to advance research in non-invasive muscle, nerve, or spinal cord stimulation treatments.Main results. OpenXstim can deliver current pulses up to 110 mA with a compliance voltage of 96 V per channel. In benchtop testing, we found that the stimulator successfully generates high frequency (9 kHz) burst stimulation, a mode commonly used for spinal cord neuromodulation. The stimulator was further tested in two individuals with SCI and showed preliminary indications of functional improvement. However, large controlled trials are needed to establish efficacy. Although special care was taken in the design of the stimulator to ensure user safety, users are strongly warned to handle the device with utmost caution, as it can generate high voltage and current that may cause adverse health effects if not used properly.Significance.This programmable, open-source stimulator offers tangible hope for improving the accessibility of non-invasive neuromodulation treatments for people with paralysis worldwide. The design and complete source-code of the stimulator are freely available online in a public repository:https://github.com/OpenMedTech-Lab/OpenXstim.