title: Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2.
abstract: OBJECTIVE
  A 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.
  
  
  METHODS
  Pre-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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  Right 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.
authors.affiliation: Laboratory for Engineering of the Neuromuscular System, Department of Electronics, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, Italy.
authors.forename: Corrado
authors.initials: C
authors.lastname: Cescon
authors.forename: Diego
authors.initials: D
authors.lastname: Riva
authors.forename: Vita
authors.initials: V
authors.lastname: Začesta
authors.forename: Kristina
authors.initials: K
authors.lastname: Drusany-Starič
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Martsidis
authors.forename: Olexander
authors.initials: O
authors.lastname: Protsepko
authors.forename: Kaven
authors.initials: K
authors.lastname: Baessler
authors.forename: Roberto
authors.initials: R
authors.lastname: Merletti
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000293:injuries* / Q000294:innervation* / Q000502:physiology; D002585:Cesarean Section; D004576:Electromyography / Q000379:methods; D004841:Episiotomy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D022125:Lacerations / Q000150:complications*; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D036801:Parturition; D049590:Postpartum Period; D011295:Prenatal Care; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult