Background & Aims
Following a traumatic spinal cord injury (tSCI), approximately 50% of individuals will develop chronic neuropathic pain (NeuP), which can greatly impact well-being and is notoriously refractory to treatment. Given that approximately half of those with chronic NeuP after tSCI do not develop NeuP symptoms until a few months or more after the injury, a preemptive analgesic approach, aimed at preventing the establishment of the abnormal central nociceptive processing associated with the onset and maintenance of chronic NeuP, may be a promising avenue for reducing this negative consequence of SCI.
The primary aim of this study was to test the ability of transcutaneous electrical nerve stimulation (TENS) to reduce the onset and/or severity of NeuP during the first year after a tSCI.
Methods
The study was a randomized, blinded trial (NCT03267810) of 16 sessions of TENS (2 sessions/week) in adults who had experienced a tSCI within the past 4 months. Participants were randomized into the treatment TENS arm (TENS; 15-mins of high-freq TENS (80Hz pulse freq, 200µsec pulse duration) followed by 15-mins of low-freq TENS (4Hz, 200µsec)), or Sham arm (Sham; 0.5mins of suprathreshold stimulation then reduced to 0 amplitude for the remaining 29.5mins). Four electrodes were used for stimulation within the dermatome at, or one above, the level of the SCI: two pads were placed paraspinally; and two pads were placed on the ventral side. Demographic information and assessments of pain symptoms (if present) were collected, and injury characteristics were extracted from medical records. Primary outcomes at 1-year post-injury included: the presence of NeuP (based on a score of ? 2 on the Spinal Cord Injury Pain Index (SCIPI) and based on expert diagnosis) and NeuP symptom severity.
Results
Twenty-seven individuals were randomized to TENS (n=13) or Sham (n=14). No significant differences in age, sex, race, or ethnicity were found between groups. There was no significant difference in the percentage of individuals with NeuP at 1-year post-SCI between the groups based on SCIPI cut-off scores for NeuP (TENS: 31%; Sham: 43%) or based on expert diagnosis (TENS: 46%; Sham: 50%). Severity of NeuP symptoms (NPSI total score) at 1 year were also not significantly different between the groups when considering all subjects (TENS median: 23; Sham median: 12.5), or when only considering those with diagnosed NeuP at 1 year (TENS n=6, median: 34.5; Sham n=7, median: 18). Additionally, no significant differences between groups were found for other pain-related outcomes (pain interference, depressive symptoms). Three people from each group reported adverse events possibly related to stimulation during the TENS treatment period (increased existing pain, prolonged dysesthesia).
Conclusions
The results of this clinical trial did not support the effectiveness of an 8-week TENS protocol initiated within four months of SCI for the prevention or reduction of chronic NeuP. However, the failure to reach the target enrollment numbers caused the study to be underpowered, and the current lack of evidence regarding optimal dosing and timing of TENS intervention for this indication warrants additional study of this low-risk, nonpharmacologic strategy to mitigate chronic NeuP in SCI.
References
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2.Vance CG, Dailey DL, Rakel BA, Sluka KA. Using TENS for pain control: the state of the evidence. Pain management. 2014;4(3):197-209.
3.Yang Y, Tang Y, Qin H, Xu J. Efficacy of transcutaneous electrical nerve stimulation in people with pain after spinal cord injury: a meta-analysis. Spinal Cord. 2022 May;60(5):375-381. doi: 10.1038/s41393-022-00776-z. Epub 2022 Mar 11. PMID: 35277650; PMCID: PMC9106573.
4.Celik EC, Erhan B, Gunduz B, Lakse E. The effect of low-frequency TENS in the treatment of neuropathic pain in patients with spinal cord injury. Spinal Cord. 2013 Apr;51(4):334-7. doi: 10.1038/sc.2012.159. Epub 2013 Jan 8. PMID: 23295472.
5.Mokhtari T, Ren Q, Li N, Wang F, Bi Y, Hu L. Transcutaneous Electrical Nerve Stimulation in Relieving Neuropathic Pain: Basic Mechanisms and Clinical Applications. Curr Pain Headache Rep. 2020 Feb 18;24(4):14. doi: 10.1007/s11916-020-0846-1. PMID: 32072323.
Presenting Author
Elizabeth Felix
Poster Authors
Elizabeth Felix
PhD
Univ of Miami, Miller School of Medicine
Lead Author
Eva Widerström-Noga
DDS
University of Miami Miller School of Medicine
Lead Author
Kevin Dalal
MD
University of Miami Miller School of Medicine
Lead Author
Katherine McManus
MS
Lead Author
Sequoia Jackson
MPH
Lead Author
Topics
- Specific Pain Conditions/Pain in Specific Populations: Neuropathic Pain - Central