Is it all central sensitization? Role of peripheral tissue nociception in chronic musculoskeletal pain.

Fibromyalgia syndrome (FM) is a highly prevalent musculoskeletal disorder that is often accompanied by somatic hyperalgesia (enhanced pain from noxious stimuli). Neural mechanisms of somatic hyperalgesia have been analyzed via quantitative sensory testing of FM patients. Results of these studies suggest that FM pain is associated with widespread primary and secondary cutaneous hyperalgesia, which are dynamically maintained by tonic impulse input from deep tissues and likely by brain-to-spinal cord facilitation. Enhanced somatic pains are accompanied by mechanical hyperalgesia and allodynia in FM patients as compared with healthy controls. FM pain is likely to be at least partially maintained by peripheral impulse input from deep tissues. This conclusion is supported by results of several studies showing that injection of local anesthetics into painful muscles normalizes somatic hyperalgesia in FM patients.