DYSFUNCTION OF ENDOGENOUS PAIN MODULATION AND SENSORY ABNORMALITIES IN PATIENTS WITH NOCICEPTIVE PAIN

Abstract
To investigate the effect of chronic nociceptive pain on endogenous pain modulation and on somatosensory perception we examined patients with painful osteoarthritis of the hip before, and when painfree following surgery. Sex- and age matched healthy subjects served as controls. The submaximal effort tourniquet test was used to induce ischemic pain in the arm and quantitative sensory testing was performed in the healthy leg before, during and 45 min following the tourniquet test to study the function of diffuse noxious inhibitory controls. The main finding was that no modulation of pressure pain sensitivity was found in patients before surgery, as opposed to controls, suggesting a dysfunction of diffuse noxious inhibitory mechanisms. Following surgery, pressure pain thresholds increased during the tourniquet test in patients and controls alike. Furthermore, increased sensitivity to innocuous warmth, pressure pain, cold pain and a tendency toward increased sensitivity to heat pain was found in the painful area of the affected leg in patients compared to controls before, but not following surgery. Our findings indicate that the dysfunction of diffuse noxious inhibitory controls and the multimodal increase in sensitivity to somatosensory stimuli had been caused and maintained by chronic nociceptive pain.

Key words
Osteoarthritis, nociceptive pain, quantitative sensory testing, diffuse noxious inhibitory controls, central sensitisation.

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