Abnormal sensitization and temporal summation of second pain (wind-up) in patients with fibromyalgia syndrome

Abstract
N FMS patients, it seems likely that a central pathophysiological process is at least partly responsible for FMS, as is the case for many chronic pain conditions. Therefore, the present study sought to obtain psychophysical evidence for the possibility that input to central nociceptive pathways is abnormally processed in individuals with long standing FMS. In particular, temporal summation of pain (wind-up) was assessed, using series of repetitive thermal stimulation of the glabrous skin of the hands. Although wind-up was evoked both in control and FMS subjects, clear differences were observed. The perceived magnitude of the sensory response to the first stimulus within a series was greater for FMS subjects compared to controls, as was the amount of temporal summation within a series. Within series of stimuli, FMS subjects reported increases in sensory magnitude to painful levels for interstimulus intervals of 2–5 s, but pain was evoked infrequently at intervals greater than 2 s for control subjects. Following the last stimulus in a series, after-sensations were greater in magnitude, lasted longer and were more frequently painful in FMS subjects. These results have multiple implications for the general characterization of pain in FMS and for an understanding of the underlying pathophysiological basis....