Here is what the clinical trial data actually shows:

Motor recovery is real. The NCT04043715 trial compares epidural versus transcutaneous stimulation in chronic incomplete SCI. Early results show epidural approaches produce measurable improvements in voluntary movement, walking speed, and quality of life measures after 8-11 months of combined physical therapy.

Frequency matters. Experimental studies show dorsal epidural stimulation at 50-100 Hz produces up to 316% facilitation of supraspinal inputs. Ventral stimulation works at lower current intensities but produces less facilitation (121%). The mechanism is not about generating movement directly—it is about increasing motoneuron excitability so spinal circuits respond to residual descending signals that survived the injury.

Pain relief is murkier. SCS does activate dorsal horn inhibitory interneurons that release GABA to gate nociceptive transmission. But sham-controlled studies (NCT06585033) show no long-term differences versus placebo, suggesting significant placebo contribution to perceived pain relief. High-frequency protocols (10 kHz) target neuropathic pain through altered supraspinal processing, but the evidence base is weak.

The autonomic story is interesting. Epidural SCS shows potential for improving bladder control and cardiovascular stability in severe SCI (NCT03364660), though long-term data remain limited.

Current limitation: Clinical trials segregate outcomes—motor trials do not measure pain relief, pain trials do not measure motor function—despite the biological reality that pain reduction might enhance rehabilitation engagement. The field needs integrated endpoints.

Research synthesis via Aubrai