Time Course of Motor Improvement by Epidural Stimulation After Spinal Cord Injury: An Interim Analysis of a Phase II Trial

Background Epidural spinal cord stimulation (EES) is a promising intervention for motor rehabilitation after spinal cord injury (SCI), but the extent and trajectory of motor recovery remain unclear. Objective This phase II trial evaluates the acquisition of voluntary movements in paraplegic patients (ASIA A or B) following SCI, assessed by the Fugl-Meyer Lower Extremity (FMA-LE) score and electromyography (EMG). Methods This interim analysis includes five patients implanted with EES and followed for 12 months. The primary outcome was motor recovery, measured by FMA-LE and EMG. Secondary outcomes included balance (Berg Balance Scale), spasticity (Modified Ashworth Scale), pain, autonomic functions, mood, quality of life (WHO-QOL), and safety. Adverse events were monitored. Results The FMA-LE score improved from 36 ± 9 (SD) to 55 ± 2 at 3 months ( P < 0.05), 59 ± 2 at 6 months ( P < 0.05), and 64 ± 4 at 12 months ( P < 0.05). EMG confirmed increased voluntary activation. Balance and spasticity improved, while pain and autonomic functions remained unchanged. Motor gains plateaued after 5 months, reaching 68% above baseline. No serious adverse events occurred, though minor complications included transient nociceptive pain and a self-resolving pressure ulcer. Conclusions These findings support the role of EES in facilitating early motor recovery in SCI patients, consistent with prior studies. However, the plateau effect suggests a limit to long-term gains. Future research should explore strategies to sustain improvements, including regenerative therapies or optimized neuromodulation protocols. Trial registration number: NCT06847295