Long-term functional recovery and immediate neuromuscular facilitation following epidural spinal cord stimulation in chronic spinal cord injury: a pilot cohort study
Background Epidural spinal cord stimulation (eSCS) has shown promise in facilitating motor recovery in chronic spinal cord injury (SCI); however, long-term functional trajectories beyond 12 months and the neurophysiological mechanisms underlying eSCS-mediated recovery remain poorly characterized. This pilot cohort study investigated the 24-month functional recovery trajectory following eSCS combined with structured rehabilitation in patients with chronic SCI and evaluated the immediate neuromuscular facilitation effects of eSCS using surface electromyography. Methods Eleven patients with chronic SCI (median age, 56 years; 90.9% male; AIS grades A-D; median time since injury, 7 years) who underwent eSCS implantation and completed at least 24 months of follow-up were included. Motor score, pinprick sensory score, Barthel Index, WISCI II, VAS for pain, and WHOQOL-BREF were assessed at baseline and at 3, 6, 9, 12, 18, and 24 months. Surface electromyography of bilateral rectus femoris and tibialis anterior was obtained 1 month post-implantation under stimulation-off and stimulation-on conditions. Longitudinal changes were evaluated using the Wilcoxon signed-rank test. Results Significant improvements were observed across all functional domains over 24 months. Median motor score increased from 60 to 66 (Δ = +6.0, p = 0.001), Barthel Index from 40 to 60 (Δ = +20.0, p = 0.001), and WISCI II from 5 to 13 (Δ = +8.0, p = 0.001). VAS decreased from 6 to 3 (Δ = −3.0, p = 0.002), and WHOQOL-BREF increased from 39 to 53 (Δ = +14.0, p = 0.001). All 11 patients (100%) exceeded minimal clinically important difference thresholds for motor function, functional independence, and ambulation; 82% achieved the threshold for pain reduction. Pinprick sensory score improved significantly from 9 months onward. Surface electromyography demonstrated immediate neuromuscular facilitation in all participants under stimulation-on conditions, with median rectus femoris and tibialis anterior facilitation ratios of 1.24 and 1.14, respectively (both p = 0.003), including in patients with motor-complete injuries. Conclusion In patients with chronic SCI, eSCS combined with structured rehabilitation produced sustained and clinically meaningful improvements across multiple functional domains over 24 months, with recovery continuing beyond the first year. These findings support eSCS as a long-term therapeutic strategy for chronic SCI and highlight the importance of extended follow-up to capture the full recovery trajectory.