title: Asymmetric sphincter innervation is associated with fecal incontinence after anal sphincter trauma during childbirth.
abstract: OBJECTIVE
  Functional asymmetry of pelvic floor innervation has been shown to exist in healthy subjects, and has been proposed to be a predictor of increased risk for fecal incontinence in case of trauma. However, this remains to be shown for different clinical conditions such as traumatic childbirth.
  
  
  METHODS
  A conventional surface EMG system was used to assess the innervation of the external anal sphincter. A symmetry index was used to define the relative EMG amplitude asymmetry of the external anal sphincter between 0 (symmetric) and 1 (asymmetric). Three cohorts were studied: 40 nulliparous women in the third trimester (Study 1), 15 primiparous women within 6 months following vaginal delivery without clinically apparent anal sphincter trauma (Study 2), and 50 women after childbirth-related third or fourth degree perineal tear 6-12 months postpartum (Study 3). Furthermore, all women underwent conventional anorectal manometry.
  
  
  RESULTS
  Sixteen or forty nulliparous women reported signs of fecal incontinence; however, relative asymmetry was not correlated to symptom severity (P = 0.345), and not to manometric measures (Study 1). In Study 2, Women who had suffered clinically apparent anal sphincter trauma (P = 0.07) tended to have a stronger association between incontinence and asymmetry. In Study 3, 19/50 women reported moderate to severe incontinence. Asymmetry and symptom severity were significantly correlated (P < 0.001). Patients with incontinence had a significantly higher asymmetry score than their continent counterparts.
  
  
  CONCLUSIONS
  Functional asymmetry of anal sphincter innervation is significantly associated with incontinence symptoms, but only after childbirth-related sphincter injuries and therefore, should be regarded as an additional risk factor.
authors.affiliation: Department of Diagnostic Radiology, University of Tübingen, Tübingen, Germany.
authors.forename: Beate M
authors.initials: BM
authors.lastname: Wietek
authors.forename: Heidemarie
authors.initials: H
authors.lastname: Hinninghofen
authors.forename: Ekkehard C
authors.initials: EC
authors.lastname: Jehle
authors.forename: Paul
authors.initials: P
authors.lastname: Enck
authors.forename: Heiko B
authors.initials: HB
authors.lastname: Franz
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000293:injuries* / Q000294:innervation*; D015331:Cohort Studies; D004576:Electromyography; D004841:Episiotomy; D005242:Fecal Incontinence / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology*; D005260:Female; D006801:Humans; D022125:Lacerations / Q000150:complications; D008365:Manometry; D007744:Obstetric Labor Complications / Q000453:epidemiology / Q000473:pathology*; D036801:Parturition; D017773:Pelvic Floor / Q000294:innervation / Q000473:pathology; D010502:Perineum / Q000293:injuries; D011237:Predictive Value of Tests; D011247:Pregnancy; D015995:Prevalence; D012307:Risk Factors; D014549:Urinary Incontinence / Q000453:epidemiology / Q000209:etiology / Q000473:pathology