The Effects of Transcranial Direct Current Stimulation on Metabolite Changes at the Thalamus in Neuropathic Pain after Spinal Cord Injury: A Pilot Study

Objective: To evaluate the pain intensity and brain metabolites, N-acetyl aspartate (NAA), myo-inositol (ml), choline (Cho), and glutamine combined glutamate (Glx) levels in the thalami after transcranial direct current stimulation (tDCS) treatment. Materials and Methods: Ten spinal cord injury (SCI) with neuropathic pain (NP) patients were given 20 minutes, 2 mA anodal tDCS over the left primary motor cortex for five consecutive days. Measures of numerical rating scales (NRS) and concentration of brain metabolites were performed before and immediately after treatment. Results: The results showed significant reduction between pre- and immediately post-treatment in NRS (–2.213, 95% CI –0.836 to –3.570; p=0.005), significant decrease in Glx/Cr concentration (–0.025, 95% CI –0.004 to –0.045; p=0.022), and significant increased in ml/Cr (0.049, 95% CI 0.014 to 0.083; p=0.012) after tDCS treatment. No statistically significant pre- to post-treatment differences in NAA/Cr or and Cho/Cr were found in the present study. Conclusion: The findings suggest that abnormal Glx/Cr and mI/Cr levels in the thalami would cause NP after SCI. The tDCS may be useful in NP reduction by returning the abnormal brain metabolites to normal. Additional research with larger sample size is warranted to evaluate this possibility. Keywords: Magnetic resonance spectroscopy, Neuropathic pain, Spinal cord injury, Transcranial direct current stimulation