Diffuse Noxious Inhibitory Control Function in Women With Provoked Vestibulodynia

OBJECTIVES: The objective of the study was to assess diffuse noxious inhibitory control (DNIC) function in women with provoked vestibulodynia (PVD) compared with healthy controls through the use of 2 different methodologies. Furthermore, the study aimed to assess whether pain characteristics correlate with DNIC in women with PVD. METHODS: Twenty-three healthy control women and 23 women diagnosed with PVD by the study gynecologist participated in the study. To assess DNIC, heat pain tolerance, determined through an ascending method of limits and temporal summation of thermal pain were used as test stimuli and a cold water bath was used as the conditioning stimulus. Participants reported on pain characteristics as potential correlates with DNIC function. RESULTS: No significant group differences were found in the number of DNIC responders per group when using heat pain tolerance or temporal summation procedures to examine DNIC. The magnitude of the DNIC response was examined for the overall groups and for positive DNIC responders only. When all participants were included in the analyses with the heat pain tolerance procedure, women with PVD displayed a higher magnitude of DNIC responding. Correlations between pain variables and DNIC responding and magnitude were nonsignificant. DISCUSSION: Results support previous findings of intact DNIC function in women with PVD, using both an ascending method of limits and a temporal summation paradigm. Pain-related variables were not correlated with DNIC function in women with PVD, perhaps this unexpected finding is due to the possibility that central processes other than DNIC, such as descending facilitation, provoke or maintain this chronic pain condition.