Perineal muscle stiffness in women with and without vulvodynia

© 2014 Melissa Jane DavidsonThe studies reported in this thesis focused upon: (i) objectively measuring the muscle stiffness of the perineal muscles of the pelvic floor in two different cohorts of women - those asymptomatic of pelvic floor dysfunction, and those symptomatic of vulvodynia; (ii) demonstrating if differences in perineal muscle stiffness existed between these cohorts; and, (iii) establishing if an association between perineal muscle stiffness and vulval pain was present in women with vulvodynia. A test-retest, intra- and inter-tester cross-sectional study of the MyotonPro™ (a myotonometer) to obtain objective measures of muscle stiffness of the perineal muscles in asymptomatic and symptomatic (vulvodynia) cohorts was conducted. The results of this study demonstrated that the MyotonPro™ showed good to very good reliability in measuring muscle stiffness in both cohorts. No difference in muscle stiffness was observed between rest and contracted muscle states which may have been due to difficulties with accuracy of measurement during the contraction state. Further research is needed to provide certainty regarding the ability to detect perineal muscle contraction accurately with the MyotonPro™. With the objective measures of muscle stiffness obtained in this study, the next stage was to compare the two cohorts. A cross-sectional study aimed to determine if differences existed in perineal muscle stiffness between the asymptomatic and symptomatic (vulvodynia) cohorts. The results of this study demonstrated significant differences between the cohorts at rest, with increased muscle stiffness in women with vulvodynia compared to women without vulvodynia. This finding confirms reports from clinical observation; that women with vulvodynia have increased muscle stiffness in the pelvic floor. This provided the rationale to investigate the association between muscle stiffness and pain in women with vulvodynia. Lastly, a cross-sectional study was performed to determine the relationship between perineal muscle stiffness and pain in women with vulvodynia, using both the Short Form McGill Pain Questionnaire and the Numeric Rating Scale for Pain. Whilst a positive correlation between muscle stiffness and pain was expected, results revealed a lack of correlation, using either tool. The lack of correlation may have been due to a number of factors including that perineal muscle stiffness and pain do not correlate in women with vulvodynia; or muscle stiffness and pain only correlate at the moment of provocation of pain; or the lack of correlation may have been due to the moderately low severity of pain reported by this cohort. In conclusion, the results of these studies have provided objective measures of muscle stiffness of the perineal muscles in women with and without vulvodynia. The cross-sectional study showed that women with vulvodynia have significantly increased muscle stiffness in their perineal muscles compared to asymptomatic women. Future studies into the effect of provocation of pain during muscle measures may provide further insight into the relationship between pain and muscle stiffness in the perineal muscles