Assessment of pain and neurological function based on transcranial magnetic stimulation in patients with acute spinal cord injury: a cross-sectional study

To examine the associations between transcranial magnetic stimulation (TMS) parameters, particularly cortical silent period (CSP) and central motor conduction time (CMCT), and pain severity and neurological impairment in acute spinal cord injury (SCI). This cross-sectional study included 74 patients with acute SCI who underwent clinical assessment and TMS within 2 weeks after injury. Pain intensity was assessed using the Visual Analog Scale (VAS), and neurological function was evaluated using American Spinal Injury Association (ASIA) motor and sensory scores. TMS was performed over the primary motor cortex, with surface electromyography recorded from the first dorsal interosseous muscles to obtain motor evoked potential (MEP) latency, CMCT, and CSP duration. Spearman correlation, multiple regression, and exploratory ROC curve analyses were applied. CSP duration correlated negatively with VAS score ( r = -0.453, P < 0.001) and remained independently associated with pain intensity ( P = 0.001). The severe pain group had significantly shorter CSP (68.26 ± 16.28 ms) than the mild/moderate groups. In exploratory ROC analysis, a CSP cutoff of 61.57 ms showed moderate discrimination for severe pain (AUC = 0.759, 95% CI 0.632–0.872; sensitivity 50.0%, specificity 92.6%). For neurological function, both CMCT ( r = -0.371, P = 0.001) and MEP latency ( r = -0.321, P = 0.005) correlated negatively with ASIA motor scores. Patients with ASIA grade C showed significantly prolonged CMCT compared with grade D ( P = 0.007). A CMCT cutoff of 15.40 ms showed moderate discrimination for more severe motor impairment (AUC = 0.769, 95% CI 0.593–0.918; sensitivity 60.0%, specificity 84.4%). Shortened CSP was associated with greater pain severity, while prolonged CMCT was associated with worse motor impairment in acute SCI. Combined assessment of CSP and CMCT may provide complementary electrophysiological information for evaluating pain and motor pathway involvement, but these exploratory findings require validation in independent and longitudinal cohorts.