Muscle pain inhibits cutaneous touch perception.

The processing of noxious and non-noxious sensations differs between chronic pain syndromes, and we believe that studies of sensory processing in the presence of pain will help to clarify the aetiology of the conditions. Here we measured in humans the threshold-level mechanosensitivity in tonic experimental muscle pain. We found (1) that muscle pain induced by hypertonic saline reduced cutaneous threshold-level mechanosensitivity at the site of pain and at the mirror site in the contralateral face, (2) that this effect outlasted the sensation of pain, (3) that it was more pronounced when the painful area was reported to be large, and (4) that the loss of mechanosensitivity was greater in males than females. Comparing our findings to results obtained with other pain models, all classes of nociceptors do not seem to have the same effect on cutaneous mechanosensitivity. The observed threshold-level hypoesthesia is consistent with the hypothesis that the increased mechanical thresholds found in clinic cases of temporomandibular disorders and cervicobrachialgia are a direct result of the activation of muscle nociceptors.