Motor Cortex Excitability in Chronic Low Back Pain

Introduction Chronic pain is associated with dysfunctional cortical excitability. Research has identified altered intracortical motor cortex excitability in Chronic Lower Back Pain (CLBP). However, research identifying the specific intracortical changes underlying CLBP has been met with inconsistent findings. In the present case-control study, we examined intracortical excitability of the primary motor cortex using transcranial magnetic stimulation (TMS) in individuals with CLBP. Methods Twenty participants with CLBP ( M age = 54.45 years, SD age = 15.89 years) and 18 age- and gender-matched, pain-free controls ( M = 53.83, SD = 16.72) were included in this study. TMS was applied to the hand motor area of the right hemisphere and motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle of the contralateral hand. Resting motor threshold (rMT) and MEP amplitude were measured using single-pulse stimulation. Short intracortical inhibition (SICI) and intracortical facilitation (ICF) were assessed using paired-pulse stimulation. Results Individuals with CLBP had significantly higher rMT (decreased corticospinal excitability) and reduced ICF compared to controls. No significant differences were found in MEP amplitude and SICI. Conclusion These findings add to the growing body of evidence that CLBP is associated with deficits in intracortical modulation involving glutamatergic mechanisms. Significance This article reports chronic lower back pain is associated with changes in intracortical excitability, specifically reduced intracortical facilitation. Furthermore, the imbalance between facilitation and inhibition may be related to pain intensity. These findings may help clinicians in the treatment of chronic pain with an increased focus on using neuromodulation techniques, targeting maladaptive intracortical facilitation, as a potential therapeutic tool in chronic pain.