Evaluation of offset analgesia in deep muscle pain

Brøndum, Pernille ; Holt, Michael

4. term

Biomedical Engineering and Informatics, Master

2014

2014-06-03

Offset analgesia (OA) has been observed as a disproportionately large decrease in pain ratings following a slight intensity decrease in noxious heat stimulation. It is of interest to investigate whether OA is a distinct feature of the heat nociceptive system. The aim of this study was to investigate the existence of OA in deep muscle pain. Seventeen healthy subjects were recruited and a standard heat OA paradigm was applied as a control measurement of the subjects. Temporal summation (TS) and conditioned pain modulation (CPM) were measured in order to assess temporal and spatial pain mechanisms. Pressure OA paradigms were applied using a tourniquet cuff. OA was defined as the minimumpain rating following an incremental decrease in noxious stimulus relative to a time-related pain rating of a constant noxious stimulus. OA was present when applying noxious heat stimulations (P < 0.001). The known temporal and spatial pain modulating mechanism TS and CPM showed normal facilitating and inhibitory systems of the subjects. In contrast, OA was absent when applying four different noxious pressure stimuli (F(3)= 0.227, P = 0.750). Within the limitations of this study the hypothesis of OA as an endogenous analgesic mechanism evoked in deep muscle pain by noxious pressure stimuli cannot be supported.

Offset analgesia ; CPM ; Temporal summation ; Computerized cuff pressure algometry

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