There is heightened interest in the effects of spinal cord stimulation (either via epidural or transcutaneous stimulation). Already almost 20 years ago, Carhart et al. 2004 and Herman et al. 2002 described the effects of epidural spinal cord stimulation combined with gait training in a single participant (male with incomplete tetraplegia, 43 years old, injury level C5-C6, AIS C, 3.5 years post-injury). The participant first underwent 12 weeks of BWSTT that resulted in some significant improvements in treadmill gait parameters although overground ambulation remained limited. Subsequently, the participant underwent surgical implantation of an epidural stimulation system placed over the T10-T12 vertebral level. BWSTT and overground gait training in combination with epidural stimulation commenced after surgical healing. The combination of epidural spinal cord stimulation with gait training resulted in a substantial improvement in treadmill gait parameters as well as in overground ambulation. The participant reported a decreased sense of effort, a doubling in walking speed, and increased walking endurance when assisted by spinal cord stimulation. This was associated with improved community and indoor functional ambulation.
More recently, Harkema et al. (2011) described the effect of epidural spinal stimulation in combination with locomotor training in a single male participant with a motor complete spinal cord injury (23 years old, injury level C7-T1, AIS B, 3.4 years post-injury) (Harkema, et al., 2011). Before implantation, the participant underwent 170 locomotor training sessions and was unable to stand or walk independently or voluntarily move his legs. A 16-electrode array was surgically placed on the dura (L1-S1 cord segments). Optimal stimulation parameters for standing and stepping were tested. With stimulation, the participant was able to maintain standing unassisted with full weight-bearing. Locomotor-like muscle activity patterns emerged when epidural stimulation was combined with body weight-supported treadmill training (but not without stimulation). Interestingly, the participant also was able to regain some ability to voluntarily move the legs (but only in the presence of the epidural stimulation). Further studies have extended these initial findings to other individuals with motor-complete SCI (Angeli et al. 2014; Rejc et al. 2015), and even allowing for recovery of voluntary leg movement and standing without the epidural spinal cord stimulation (Reck and Landmann 2017).