Pain relief: strong evidence

A meta-analysis of 8 randomized controlled trials (777 patients) found spinal cord stimulation produces sustained pain relief for conditions like failed back surgery syndrome and chronic pancreatitis. Responder rates exceed 80%, with pain scores dropping 5-6 cm on visual analog scales maintained over 24 months (Kumar & Rizvi, 2020).

The mechanism is well understood: SCS activates large-diameter afferent fibers in the dorsal column, triggering gate control inhibition of nociceptive transmission. High-frequency variants (10 kHz) may also alter brain activity patterns in pain-processing regions.

Real-world impact: disability scores drop 30+ points, and about 40% of patients reduce opioid use.

Motor recovery: early feasibility at best

Epidural electrical stimulation (EES) for spinal cord injury is a different story. The same hardware positioned over lumbosacral regions can increase excitability of spared neural circuits, amplifying weak signals from residual descending pathways and activating central pattern generators.

Completed feasibility studies (n=2, NCT02592668/NCT02503787) showed improvements in volitional movement and spasticity reduction after 50 weeks of EES plus intensive rehabilitation. The STIMO trial demonstrated closed-loop EES with robotic-assisted training enabled overground walking in some patients.

But these are small pilot studies without adequate controls. Sample sizes are under 20. No completed pivotal trials exist comparing EES plus rehab versus rehab alone.

Why the gap?

Pain relief works through a relatively simple circuit: activate dorsal column fibers, inhibit pain transmission. The nervous system does the rest.

Motor recovery requires rebuilding complex sensorimotor integration. EES does not repair damaged axons—it makes surviving circuits more excitable. That helps, but it cannot replace lost connections.

Clinical outcomes reflect this: WISCI II walking scale improvements are modest, spasticity scores improve, but true functional independence remains rare. One systematic review found insufficient evidence for combined SCS-physiotherapy protocols specifically targeting motor outcomes.

The honest take

Spinal cord stimulators are proven technology for chronic pain. For motor recovery after SCI, they are promising but unproven. The evidence gap is real—years of large RCTs versus small feasibility studies.

Both applications use electricity to modulate neural circuits. But restoring movement requires more than modulation. It requires reconstruction. Until we can regrow axons or replace lost neurons, stimulation can only do so much.

Research synthesis via Aubrai