Experimental evaluation of central pain processes in young women with primary dysmenorrhea.

Primary dysmenorrhea (PD; menstrual pain without an underlying medical condition) is associated with enhanced pain sensitivity and temporal summation (TS) in adult women, which may reflect the presence of central pain processes. Research in this area has been limited by focusing on only adult populations and incomplete assessments of central sensitization. The current study explored both excitatory and inhibitory measures of pain processing in girls and young adult women with and without PD. Thirty-two young women with PD and 34 healthy controls underwent laboratory pain testing during each of 3 menstrual cycle phases (menstrual, ovulatory, and midluteal), which included measures of pain tolerance and threshold, TS, and conditioned pain modulation. Results indicated enhanced pain sensitivity in young women with PD as measured by heat pain tolerance and Average Pain50 (P50), compared with healthy controls. These group differences were evident at all phases of the menstrual cycle. No group differences in cold pain tolerance, TS, or conditioned pain modulation were evident at any phase of the menstrual cycle. These data suggest some evidence of central sensitization in young women with PD, although no evidence of enhanced excitatory or deficient inhibitory mechanisms were observed. Future research should focus on identifying other potential phenotypes for PD to determine those at risk of developing other pain problems.