Multichannel EMG evaluation of anal sphincter pre and post vaginal delivery: results of an international study

Riva, Diego and Raimondi, Eleonora Ester and Cescon, Corrado and Merletti, Roberto and Začesta, Vita (2012) Multichannel EMG evaluation of anal sphincter pre and post vaginal delivery: results of an international study. In: XX FIGO World Congress of Gynecology and Obstetrics. International Journal of Gynecology and Obstetrics, 7-12 October 2012, Rome, Italy.

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Objectives: Recent studies demonstrated that there is a significant correlation between anal sphincter damage during vaginal birth, with or without episiotomy, and subsequent development of anal incontinence in women. Mediolateral episiotomy is usually performed on the right side. Knowledge of the location of the innervation zones (IZs) could avoid to perform episiotomy in innervation regions: this could presumably reduce the incidence of sphincter damage and anal incontinence. The aim of the TASI-2 project was to evaluate the effect of delivery related trauma on the external anal sphincter (EAS) muscle with surface electromyography (EMG). Materials: Five hundred primiparae women participated to the study. Nine clinical partners from five European Countries (Germany, Italy, Latvia, Slovenia, Ukraine) were involved in this multicenter study coordinated by the Lab for Eng. of the Neuromuscular System (LISiN). EMG measurements were performed with a rectal probe including 16 silver electrodes spaced along the circumference. The measurements were performed at the 28th-34th gestational week and 6-8 weeks after delivery. 328 women concluded the experimental protocol. Methods: The subjects were asked to perform a maximal voluntary contraction (MVC) of the EAS for 10s. The innervation zones of single motor units were identified by means of a recently developed surface EMG decomposition algorithm. The know the site and the extension of episiotomy, gynaecologists involved in the study were asked to draw a picture of the episiotomy in a standard form. Results: All episiotomies were performed on right side, except three on the left and three in the midline. In women who underwent mediolateral right episiotomy (82 up to date), a statistically significant reduction of the number of IZs was observed, after delivery, in the right ventral quadrant, corresponding to the side of episiotomy, while women who had Caesarean section did not present any significant change in the innervation pattern. Conclusions: The results of the present study showed that pregnant women could have a fast and reliable clinical test which would provide indications about their sphincter innervation pattern. This information could help the obstetricians to choose which side would be preferable for performing episiotomy if this intervention will be deemed necessary at the time of delivery.

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