Background & Aims

Chronic low back pain (CLBP) is the most prevalent chronic pain condition worldwide and a major contributor to years lived with disability. Transcranial direct current stimulation (tDCS) involves applying a fixed low-intensity electric current (e.g., 1–2 mA) to the brain via electrodes placed on the scalp, between which an electric field is established. tDCS has been used to reduce pain in a range of chronic pain states. Advantage of using tDCS is its affordability and the ability to modulate underlying neural activity of brain. Studies have also shown the influence of expectations on tDCS intervention outcomes through placebo or Hawthorne like effects (1-5). Therefore this study aimed to evaluate the effect of high expectation priming of tDCS on pain reduction and related disability in patients with non-specific CLBP.

Methods

Twenty-two individuals (average age 45.6) with chronic low back pain CLBP were divided into active and sham tDCS groups (n=11 each). The anode was positioned on M1 at C3, while the cathode was placed on the opposite supraorbital region. Both groups underwent 20-minute sessions for 6 consecutive days. The active group received 2mA tDCS with a 30-second ramp up and down, while the sham group had a 30-second initial ramp up for sensory stimulation and remained inactive for the remaining 19 minutes to match the active group’s total time. Prior to the intervention, both groups were informed about receiving a brain stimulation known for pain reduction lasting weeks. Pain levels were assessed using a visual analogue scale (VAS) at baseline, day 6, and 2 weeks post-intervention. Disability was evaluated using the Roland-Morris Disability Questionnaire (RMDQ).

Results

An independent-samples t-test was conducted to compare scores of VAS and RMDQ in active and sham groups with p < 0.05. There was no significant difference between the scores of VAS for active (3.65 ± 0.77) and sham (4.10 ± 0.49) groups; t(22) = 1.702, p = 0.102. RMDQ scores were statistically non significant between active (8.08 ± 2.02) and sham (9.66 ± 2.83) stimulation groups; t(22) = 1.574, p = 0.129. A repeated measures ANOVA was performed to compare the effect of active and sham tDCS on the scores of VAS from baseline to the end of week 2. There was a statistically significant difference in the scores of VAS in active tDCS group (F (2) = 13.37, p = 0.012 whereas for sham tDCS group, it was not significant (F (2) = 4.92, p = 0.107.

Conclusions

Expectation of results influences outcomes in chronic pain states following tDCS possibly as a result of psychological factors like emotional state of the person and motivational responsiveness towards the intervention. Prior knowledge and experience of tDCS intervention can also play a role in influencing the outcomes of the intervention. Future studies can compare pain outcomes between high and low expectation priming in active and sham tDCS conditions. We conclude that expectation of results does influences outcomes in chronic pain states following tDCS.

References

1. Rabipour, S., Vidjen, P. S., Remaud, A., Davidson, P. S. R., & Tremblay, F. (2019). Examining the Interactions Between Expectations and tDCS Effects on Motor and Cognitive Performance. Frontiers in neuroscience, 12, 999. https://doi.org/10.3389/fnins.2018.00999

2. Corti, E. J., Nguyen, A. T., Marinovic, W., Gasson, N., & Loftus, A. M. (2022). Anodal-TDCS over Left-DLPFC Modulates Motor Cortex Excitability in Chronic Lower Back Pain. Brain sciences, 12(12), 1654. https://doi.org/10.3390/brainsci12121654

3. Luedtke, K., Rushton, A., Wright, C., Geiss, B., Juergens, T. P., & May, A. (2012). Transcranial direct current stimulation for the reduction of clinical and experimentally induced pain: a systematic review and meta-analysis. The Clinical journal of pain, 28(5), 452–461. https://doi.org/10.1097/AJP.0b013e31823853e3

4. Antal, A., Alekseichuk, I., Bikson, M., Brockmöller, J., Brunoni, A. R., Chen, R., Cohen, L. G., Dowthwaite, G., Ellrich, J., Flöel, A., Fregni, F., George, M. S., Hamilton, R., Haueisen, J., Herrmann, C. S., Hummel, F. C., Lefaucheur, J. P., Liebetanz, D., Loo, C. K., McCaig, C. D., … Paulus, W. (2017). Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, 128(9), 1774–1809. https://doi.org/10.1016/j.clinph.2017.06.001

5. O’Connell, N. E., Marston, L., Spencer, S., DeSouza, L. H., & Wand, B. M. (2018). Non-invasive brain stimulation techniques for chronic pain. The Cochrane database of systematic reviews, 3(3), CD008208. https://doi.org/10.1002/14651858.CD008208.pub4

Presenting Author

Nikhil Choudhary

Poster Authors

Nikhil Choudhary

Lead Author

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Topics

  • Specific Pain Conditions/Pain in Specific Populations: Low Back Pain