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

Abstract

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.