Deep and Superficial Pelvic Floor Muscle Responses to a Pain Stimulus in Vestibulodynia
MetadataShow full item record
Previous studies have suggested that protective responses in the pelvic floor muscles (PFMs), described in terms of hypertonicity and over-reactivity, are associated with and may worsen the symptoms of provoked vestibulodynia (PVD, i.e., chronic vulvar pain). A recent study reported that, upon manual palpation of the PFM, hypertonicity was consistently found in the superficial but not the deep PFM layers. The goals of this study were to compare superficial and deep PFM resting tone, protective response magnitude and onset timing to moderate perceived vulvar pain between women with and without PVD. Eleven women with PVD and eleven control women Tcompleted a gynecological examination and standardized PFM electromyography (EMG) testing. Three trials of sTurface EMG activity of the PFM were recorded while a pressure-pain stimulus (PPS) was applied to the vulvar vestibule. Increasing pressure was applied to achieve a perceived pain intensity rating of 6/10 using an 11-point numerical rating scale presented visually. The women with PVD had higher resting EMG activity in their superficial PFMs (p=0.04) as compared to the control group, while no difference was found at the level of the deep PFMs (p=0.12). Participants in both groups demonstrated contractile responses to the PPS in both the superficial and the deep PFM, and these responses were significantly higher (p=0.0001) in the superficial (50.06 vs 38.69 % maximal voluntary electrical activation [MVE]) as compared to the deep (24.88 vs 22.52 %MVE) PFM layers. Women with PVD had significantly higher PFM responses at the superficial layer as compared to the control women (p<0.0005). The onset of the superficial and deep EMG PFM responses followed the PPS application in both groups. No differences were found between the deep and superficial PFM onset latency to the timing of the PPS application.The results of this study suggest that women with PVD have superficial PFMs that are more responsive to vulvar pain than those in non-affected women. The findings also suggest that superficial PFM over-reactivity, rather than deep PFM over-reactivity, is part of the PFM dysfunction reported in women with PVD.