The major clinical application of spinal cord stimulation is the control of neurological pain and of impaired motor functions. Until recently, spinal cord stimulation in humans was only possible with epidural electrodes implanted close to the back side of the spinal cord. With the development of transcutaneous spinal cord stimulation, a non-invasive technique using skin electrodes placed over the lower back and abdomen became available.
Transcutaneous spinal cord stimulation activates large-diameter afferents of posterior roots of several lumbar and upper sacral spinal cord segments. Single pulses evoke brief contractions of effectively all lower limb muscles bilaterally – so-called posterior root-muscle reflexes (PRM reflexes). Physiologically, PRM reflexes are closely related to the H reflex. The method hence allows for new designs of human neurophysiological studies, both in people with and without neurological conditions.
The consistent stimulation of sensory nerve fibers of multiple posterior roots further allows for the application of transcutaneous lumbar spinal cord stimulation as a neuromodulation technique. The potential of its therapeutic relevance in spasticity control and enhancement of residual motor control after spinal cord injury is currently being investigated, and first results are very promising.
For further details and references, see expanded document (with references): Transcutaneous spinal cord stimulation_long