Diego Riva

Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2

Introduction and hypothesisA correlation exists between external anal sphincter (EAS) damage during birth and the subsequent development of fecal incontinence. This study evaluated the effect of delivery-related trauma on EAS innervation by means of intra-anal EMG performed with a rectal probe with 16 silver electrodes equally spaced along the circumference, before and after delivery.MethodsPre-partum EMG measurements were performed on 511 women, by nine clinical partners from five European countries at the 28th to 34th gestational weeks and the 6th to 8th post-delivery weeks; 331 women returned, after delivery, for the second test. The innervation zones (IZ) of EAS single motor units were identified by means of an EMG decomposition algorithm.ResultsThe subjects were divided into four groups according to the delivery mode (Caesarean, vaginal with no evident damage, spontaneous lacerations and episiotomies). The number of IZs before and after delivery was compared. In the 82 women who underwent right mediolateral episiotomy, a statistically significant reduction of IZs was observed, after delivery, in the right ventral quadrant of the EAS (side of the episiotomy). Women who had Caesarean section, spontaneous lacerations or lack of evident damage did not present any significant change in the innervation pattern.ConclusionsRight episiotomy reduces the number of IZs on the right-ventral side of the EAS. The fast and reliable test proposed indicates the sphincter innervation pattern before delivery and helps obstetricians to evaluate the risks and to choose the preferred side of the episiotomy, if deemed necessary at the time of delivery.

The correct episiotomy: Does it exist?

Dear Sir, The article BThe correct episiotomy: Does it exist? A crosssectional survey of four public Israeli hospitals and review of the literature,^ byDr. Lena Sagi-Dain and Dr. Shlomi Sagi [1], published in a recent issue of International Urogynecology Journal, adds a contribution to the extensive body of experience and experimental knowledge concerning a very controversial issue [2]. Additional knowledge recently came from two works dealing with the innervation of the external anal sphincter (EAS) and its alteration by episiotomy (European Project OASIS and Multicenter Study TASI) [3, 4]. According to the principle primum non nocere (first, do no harm) the Bcorrect^ episiotomy, if any, is the one that maximizes benefits with no, or minimal, harm. As reported in [3, 4], episiotomy may seriously damage the innervation of the EAS. The harm done may not be immediately and functionally evident without proper electrophysiological assessment because of the redundancy of muscle control, which is progressively reduced by aging. The risk of iatrogenic harm may be minimized by preventive assessment of EAS innervation, which has high intersubject variability and must be assessed during pregnancy, on a case-by-case basis, in order to decide what to do in case of need at the time of delivery and acquire informed consent of the patient. The correct episiotomy, if any, is the one taking into account predelivery analysis of innervation and performed, if necessary, on the side of minimal or absent innervation of the ventral (perineal) side of the EAS. In addition, the shorter the cut, the lower the likelihood of damage of the EAS innervation. Information about new techniques and results of international projects should be provided to all clinical operators through initiatives of dissemination, continuing education, and training.

O575 MULTICHANNEL EMG EVALUATION OF ANAL SPHINCTER PRE AND POST VAGINAL DELIVERY: RESULTS OF AN INTERNATIONAL STUDY

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.