The Comparison of the Effect of High-frequency and Placebo Transcutaneous Electrical Nerve Stimulation (TENS) on the electrical brain activity

Background and Objective: Transcutaneous electrical nerve stimulation (TENS) is a noninvasive, inexpensive and safe analgesic technique used for relieving acute and chronic pain. Despite all its advantages, there has been, so far, limited scholarly research upon the extrasegmental mechanisms of TENS as well as its therapeutic effects on electrical brain activity. The aim of this study was to compare the effect of high frequency and placebo TENS on the electrical brain activity of 2 healthy groups after inducing ischemic pain. Materials and Methods:This was an interventional single-blind study conducted on 30 right-handed healthy volunteers (15 in each group). The Submaximal effort tourniquet test (SETT) was used for inducing ischemic pain. The Electroencephalogram (EEG) with 19 active channels was employed in closed eyes condition for recording of electrical brain activities. The high frequency TENS was set to 100 Hz with a pulse duration of 150µs and low intensity. In the placebo TENS group, however, those of the high frequency TENS were used but with no current output. Pain intensity was assessed using Visual Analog Scale (VAS). The EEG recording was performed for 2 minutes, followed by the induction of an ischemic pain in the left hand by SETT. Then, the pain intensity was determined and EEG was recorded for another 2 minutes. After that, one type of TENS was applied for 20 minutes, immediately followed by assessing pain intensity. Again the EEG was recorded for 2 minutes. At this stage, after terminating the induction of pain, and observing that subject’spain fell to zero on VAS, the EEG was recorded for 2 minutes again. The achieved meanpower of alpha wave was used for determining the electrical brain activity. The means was assessed by MATLAB software. The Kolmogorov-Smirnov and 2-way repeated-measures analysis of variance (ANOVA) tests were used to check the normal distribution of the data and to evaluate the trend of changes in mean power of alpha waveunder different conditions in the studied groups, respectively. Paired T- test was used to compare the intensity of pain. A significant level was considered for all cases of P<0.05.Findings: This study showed that the induced ischemic pain reduced the mean power of alpha wave. In addition, the use of high frequency and placebo TENS caused an increase in mean power of alpha wave. The intensity of pain after applying TENS, compared with that after inducing pain, decreased significantly in 2 groups. Conclusion:The findings of the study showed that the induction of ischemic pain and application of TENS led to some changes in the electrical brain activity. The pattern of these changes can be used as a brain marker for the diagnosis and treatment of pain.

کلیدواژه ها:

Transcutaneous electrical nerve stimulation (TENS) ، Visual Analog Scale (VAS) ، Electroencephalogram (EEG) ، pain measurement