The effect of negative expectations on secondary hyperalgesia

Details

Supervisors

Mouraux, André ; van den Broeke, Emanuel

Faculty

Faculté des sciences de la motricité

Degree label

Master [60] en kinésithérapie et réadaptation

Abstract

Background: When skin tissue is injured, sensitivity increases not only at the level of the injured skin site (primary hyperalgesia) but also around the injured site (secondary hyperalgesia). Secondary hyperalgesia results from central sensitization in humans. In the present study, we investigate if negative expectations about upcoming pain will increase the area and intensity of pain-induced secondary hyperalgesia. Methods: 50 healthy volunteers took part in this within- and between-subjects experiment and were allocated either to a control condition or to a nocebo condition. Each of them received a patch containing water on their right ventral forearm for 5 minutes. Participants in the nocebo group were told that their patch contains a solution of capsaicin and ethanol that would sensitize the skin. Participants in the control group were told that their patch contained water which has no effect on the skin. Each participant then received high-frequency electrical stimulation (HFS) to induce secondary hyperalgesia at the same site at which the patch had been applied. In the two independent conditions (nocebo and control), we applied pinprick stimuli before, directly after and 30 minutes after HFS to the non-conditioned surrounding skin site. The reported pain intensity was measured using a numerical rating scale (NRS). Primary outcomes were the perceived intensity and area of secondary hyperalgesia. Results: Our results show no difference between the two groups regarding the perceived intensity and the area of secondary hyperalgesia. The nocebo group did not experience more pain during HFS or more fear prior to HFS compared to the control group. Conclusion: Future investigations are required to determine the potential relation between negative expectations and central sensitization and provide new methods for efficient interventions in long lasting pain treatment.