Electrical high-frequency stimulation of the human thoracolumbar fascia evokes long-term potentiation-like pain amplification

Abstract

Nociceptive long-term potentiation, a use dependent increase in synaptic efficacy in the dorsal horn of the spinal cord is thought to contribute to the development of persistent pain states. So far, no study has analyzed the effects of high-frequency stimulation (HFS) of afferents from deep tissues (muscle and fascia) on pain perception in the back in humans. In 16 healthy volunteers, the multifidus muscle and the overlying thoracolumbar fascia were stimulated with electrical high-frequency pulses (5 × 100 pulses at 100 Hz) through bipolar concentric needle electrodes placed at lumbar level (L3/L4). Electrical pain thresholds were lower (P < 0.001) and pain ratings were higher for fascia compared with muscle stimulation (P < 0.05). For both tissues, pain ratings increased significantly across the five 100 Hz trains (from 15 to 22 numerical rating scale for fascia, from 8 to 12 numerical rating scale for muscle; both P < 0.01). Fascia HFS increased fascia pain ratings 2.17 times compared with the unconditioned control site (P < 0.001), but had no significant effect on pain sensitivity of the muscle. The HFS in muscle had no significant effect on muscle pain, but decreased pain sensitivity of the overlying fascia by 20% (P < 0.05). In additional experiments using the same electrodes and followed over >60 minutes post-HFS, potentiation by fascia HFS was similar to that of skin HFS. These findings show that the spinal input from the fascia can induce long-term changes in pain sensitivity for at least 60 minutes making it a candidate potentially contributing to nonspecific low back pain.

The Lumbodorsal Fascia as a Potential Source of Low Back Pain: A Narrative Review

“…The electrical pain threshold of the LF (3.02 ± 1.92 mA) was shown to be considerably lower than that of the erector spinae muscle (8.54 ± 5.57). Moreover, analogous to the findings concerning chemical stimulation, the controlled electrical irritation of fascial low back tissue leads to stronger pain reactions than the stimulation of the lumbar muscles [24]. …”

Assessment of pain quality reveals distinct differences between nociceptive innervation of low back fascia and muscle in humans

“…Single stimuli at twice the magnitude of the individual pain threshold and trains of high-frequency stimuli (100 Hz for 1 second) at 10 times the individual electrical detection threshold were used to elicit pain. 14 , 17 , 25 For more details, see Ref. 25 .…”

“… 24 Hypertonic saline activated a subset of chemosensitive nociceptive afferents. The present study explored the ability of verbal descriptors to discriminate the pain qualities induced by a broader spectrum of nerve fibers in muscle and fascia (by electrical stimulation 25 ) or skin (data from Ref. 13 ).…”

Rewiring of Developing Spinal Nociceptive Circuits by Neonatal Injury and Its Implications for Pediatric Chronic Pain

“…Furthermore, pharmacological agents that prevent the generation of spinal LTP also reduce behavioral pain hypersensitivity after injury [ 58 ]. Critically, the administration of LTP induction protocols involving high-frequency stimulation has been shown to increase pain sensitivity in humans [ 63 , 64 , 65 ]. Therefore, one potential mechanism by which neonatal injury could ”prime” mature nociceptive circuits is by persistently facilitating LTP at sensory synapses onto lamina I projection neurons.…”