Motor Cortex rTMS Alleviates Pain and Comorbid Depression After Spinal Cord Injury with a Correlate in M1 Intracortical Inhibition

Abstract

Purpose Neuropathic pain (NP) after spinal cord injury (SCI) is a debilitating syndrome, yet current treatments demonstrate limited efficacy. This randomized, double-blind, sham-controlled study investigated the analgesic efficacy of high-frequency repetitive transcranial magnetic stimulation (rTMS) over the left primary motor cortex (M1) and its neurophysiological mechanisms. Patients and Methods Twenty-nine SCI patients with NP were randomly assigned (3:1) to receive either active rTMS (10 Hz, a total of 1200 pulses at an intensity of 80% resting motor threshold) or sham rTMS over the left M1 corresponding to the hand area once daily for two weeks. Pain intensity (Numeric Rating Scale, NRS), depression (9-item Patient Health Questionnaire, PHQ-9), and anxiety (7-item Generalized Anxiety Disorder Questionnaire, GAD-7) were assessed at baseline and after treatment. Furthermore, M1 intracortical excitability parameters, including short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), were measured using paired-pulse TMS (ppTMS). Results After the two-week intervention, active rTMS significantly reduced NRS scores (P < 0.001), PHQ-9 scores (P = 0.023), and GAD-7 scores (P = 0.002), and significantly increased both SICI and ICF values (P < 0.001 for both). Interestingly, the baseline NRS scores were correlated with the PHQ-9 scores (r = 0.392, P = 0.032) and the SICI values (r = −0.458, P = 0.017), and changes in the NRS scores correlated with changes in the PHQ-9 scores (r = 0.436, P = 0.025) and the SICI values (r = −0.571, P = 0.004). Conclusion These findings indicate that high-frequency rTMS alleviates NP and comorbid depression after SCI and is accompanied by changes in M1 intracortical inhibition. However, the 3:1 allocation resulted in a small sham group and limited statistical power for between-group comparisons, and confirmation in larger trials is required.