Identifying the optimal electrical stimulation protocol for the induction of secondary hyperalgesia in humans.

Details

Supervisors

Mouraux, André ; van den Broeke, Emanuel

Faculty

Faculté des sciences de la motricité

Degree label

Master [60] en kinésithérapie et réadaptation

Abstract

Central sensitization is what happens when the nociceptive neurons responses is increased in the central nervous system. Therefore, people feel pain with stimulus that shouldn’t be painful (allodynia) or disproportionate pain with low painful stimulus for healthy humans (hyperalgesia). Central sensitization could be the source of chronic pain. In order to assess central sensitization in humans, we induced high-frequency burst-like electrical stimulation (HFS) on forearm of healthy volunteers. The purpose was to measure the increase in mechanical pinprick sensitivity onto the conditioned area, and in the surrounding of the electrode. We aimed to define the optimal parameters of the electrical stimulation concerning pulse shape and mostly frequency. In experiment 1 HFS was induced with a non-charge-compensated versus charge-compensated pattern; it turned out there was no significant difference in the increase of pinprick sensitivity between both stimulations. In experiment 2, the stimulation was induced in four groups with respectively 5, 20, 42 and 100 Hz. The medium ranges of frequency stimulation (20 and 42 Hz) generated a significant higher pinprick sensitivity than low frequency stimulation (5 Hz). Only 42 Hz generated higher increase of pinprick sensitivity than high frequency stimulation (100 Hz). A possible theory is the greater amount of substance P released by the firing of C-fibers at these frequencies, that binds with NK1 receptors, and triggers more pain.