Background: Neither the cause of vaginismus nor the muscles involved are precisely identified.
Aim: To define the involved muscles and their role in the pathogenesis of vaginismus.
Methods: The EMG activity of the levator ani (LA), puborectalis (PR) and bulbocavernosus (BC) muscles was studied in seven female patients (age (years): 25.6(mean)+/-1.2(S.D.)) and seven healthy volunteers who matched the patients in age. Recordings were performed at rest and during induction of vaginismus by a vaginal dilator.
Main results: Upon approximating the vaginal dilator to the vaginal introitus or introducing it into the vagina of the healthy volunteers, the EMG activity of the LA, PR and BC muscles showed no significant difference from the basal activity. In the patients, the basal EMG activity of the examined muscles was significantly higher than that of the healthy volunteers (P<0.05). Upon vaginismus induction, the muscles showed a significant increase of the EMG activity (P<0.01). The latency recorded a mean of 14.2+/-2.3, 13.9+/-2.3 and 14.1+/-2.2ms (P>0.05) in the LA, PR and BC muscles, respectively. The muscle response was momentary lasting a mean of 31.2+/-5.7s. It was reproducible provided an off-time of a mean of 13.2+/-2.3s was observed.
Conclusion: The pelvic floor muscles of vaginismus patients exhibited increased EMG activity at rest and on vaginismus induction; the cause is unknown. The concept of a disordered sacral reflex arc is put forward but needs further studies to be verified.