Abstract
Fibromyalgia syndrome (FMS) is characterized by widespread pain, fatigue, sleep abnormalities, and distress. Because FMS lacks consistent evidence for tissue abnormalities, recent investigations have focused on central nervous system mechanisms of pain. Abnormal temporal summation of second pain (“windup”) and central sensitization (CS) have recently been described in FMS patients. Windup (WU) and central sensitization, which rely on central pain mechanisms, occur after prolonged C-nociceptor input and depend on activation of nociceptor specific neurons as well as wide dynamic range neurons in the dorsal horn of the spinal cord. The important role of WU is also supported by its ability to predict the clinical pain intensity of FMS patients. Furthermore, brain-imaging techniques that can detect neuronal activation following nociceptive stimuli have provided additional evidence for abnormal central pain mechanisms in FMS. Most importantly, brain images have corroborated the augmented reported pain experience of FMS patients during experimental pain stimuli. These findings may have important implications for future research as well as the treatment of FMS pain.