title: Topography of the extrinsic internal anal sphincter nerve supply during laparoscopic-assisted TAMIS TME: five key zones of risk from the surgeons' view.
abstract: OBJECTIVE
  Sparing the extrinsic autonomic innervation of the internal anal sphincter during total mesorectal excision is important for the preservation of anal sphincter function. This study electrophysiologically confirmed the topography of the internal anal sphincter nerve supply during laparoscopic-assisted transanal minimally invasive surgery for total mesorectal excision.
  
  
  METHODS
  This prospective study was conducted at two large multispecialty referral centers. Six patients (five males and one female) aged between 45 and 65 years with low rectal cancer (≤5 cm from the anal verge) were enrolled. Surgery was performed under electric stimulation of the pelvic autonomic nerves with observation of the electromyographic signals of the internal anal sphincter.
  
  
  RESULTS
  The minimally invasive transanal surgical approach enabled advantageous visualization of the pelvic autonomic nerves in all patients. In particular, extrinsic innervation to the internal anal sphincter near the levator muscle was consciously spared under electrophysiological confirmation. The evoked absolute electromyographic amplitudes of the internal anal sphincter during transanal minimally invasive surgery were significantly lower than the initial results of the laparoscopic approach [3.7 μV (interquartile range 2.4; 5.7) vs. 4.3 μV (interquartile range 3.1; 8.6); p = 0.002]. Five key zones of risk for pelvic autonomic nerve damage were identified. No complications occurred.
  
  
  CONCLUSIONS
  The electromyographic results of this preliminary study indicate advantages for sparing the internal anal sphincter innervation during transanal minimally invasive mesorectal dissection considering the specific in situ neuroanatomical topography.
authors.affiliation: Department of General, Visceral and Transplant Surgery, University Medical Center, Johannes Gutenberg University of Mainz, Langenbeckstraße 1, 55131, Mainz, Germany, werner.kneist@unimedizin-mainz.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Kneist
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Rink
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Kauff
authors.forename: Moritz A
authors.initials: MA
authors.lastname: Konerding
authors.forename: Hauke
authors.initials: H
authors.lastname: Lang
mesh_terms: D000368:Aged; D001003:Anal Canal / Q000294:innervation*; D017776:Autonomic Pathways / Q000033:anatomy & histology* / Q000293:injuries; D004576:Electromyography; D005260:Female; D006801:Humans; D010535:Laparoscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000601:surgery*; D012007:Rectum / Q000601:surgery*; D012307:Risk Factors