The Role of Maladaptive Plasticity in Modulating Pain Pressure Threshold Post-Spinal Cord Injury

Background: Spinal cord injury (SCI) frequently leads to pain, leading to significant disability. Pain sensitization, a key feature of SCI, is commonly assessed via quantitative sensory testing like the Pressure Pain Threshold (PPT), though the factors influencing PPT changes remain unclear. This study hypothesizes that specific clinical and neurophysiological factors modulate PPT in SCI patients. The primary objective is to identify predictors of PPT in SCI patients. Methods: We conducted a cross-sectional analysis of neurophysiological, clinical, and demographic data from 102 SCI patients in an ongoing prospective cohort study called “Deficit of Inhibition as a Marker of Neuroplasticity” (DEFINE study). Multivariable regression analyses were used to evaluate demographic, clinical, and functional variables associated with PPT, the primary outcome measure. Results: The sample comprised 87.9% males with an average age of 41. Trauma was the leading cause of SCI (77.45%), predominantly affecting the cervical and thoracic levels. Pain was reported by 44% of participants, and the mean PPT was 8.3 kPa, measured bilaterally. Multivariate analysis of PPT in the left, right, and bilateral thenar regions revealed consistent trends. Significant negative associations were found between bilateral PPT and low beta EEG frequency in the central area (β = −14.94, p = 0.017), traumatic lesion etiology (β = −1.99, p = 0.038), and incomplete lesions by the American Spinal Injury Association classification (β = −1.68, p = 0.012). In contrast, positive associations were observed with age (β = 0.08, p < 0.001). Conclusions: Our findings show that increased beta oscillations and traumatic brain injury having a lower PPT indicate that factors associated with maladaptive plasticity are associated with decreased and likely less functional PPT. On the other hand, increased motor function may help to regulate PPT in a more functional status.