title: Recurrent laryngeal nerve recovery patterns assessed by serial electromyography.
abstract: OBJECTIVE
  Following acute injury to the recurrent laryngeal nerve (RLN), laryngeal electromyography (LEMG) is increasingly being used to determine prognosis for recovery. The LEMG findings change during the recovery process, but the timing of these changes is not well described. In this canine study, LEMGs were obtained serially following model RLN injuries.
  
  
  METHODS
  Animal Study.
  
  
  METHODS
  Thirty-six canine RLNs underwent crush (n = 6), complete transection with reanastomosis (n = 6), half-transection half-crush (n = 5), cautery (n = 5), stretch (n = 5), inferior crush (n = 4), or inferior transection with reanastomosis (n = 5) injuries. Injuries were performed 5 cm from cricoid or were 5 cm further inferior. Under light sedation, LEMG of thyroarytenoid muscles was performed monthly for 6 months following injury. At 6 months, spontaneous and induced vocal fold motion was assessed.
  
  
  RESULTS
  Except for the stretch injury, the remaining groups showed very similar recovery patterns. Fibrillation potentials (FPs) and/or positive sharp waves (PSWs; signs of bad prognosis) were seen in all cases at 1 month and lasted on average for 2.26 months (range = 1-4 months). Motor unit potentials of at least 2+ (scale = 0-4+; signs of good prognosis) were seen beginning at 3.61 months (range = 2-6 months). The stretch injury was less severe, with 3 of 5 showing no FPs/PSWs at 1 month; all recovered full mobility. Ten of the 36 thyroarytenoid muscles (27.8%) had 1 electromyograph showing both bad prognosis and good prognosis signs simultaneously at 2 to 4 months postinjury.
  
  
  CONCLUSIONS
  LEMG can be used to predict RNL recovery, but timing is important and LEMG results earlier than 3 months may overestimate a negative prognosis.
  
  
  METHODS
  NA Laryngoscope, 126:651-656, 2016.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery.
authors.forename: Randal C
authors.initials: RC
authors.lastname: Paniello
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Park
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery.
authors.forename: Neel K
authors.initials: NK
authors.lastname: Bhatt
authors.affiliation: Department of Neurology, Washington University School of Medicine, Saint Louis, Missouri, U.S.A.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Al-Lozi
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D004576:Electromyography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D007828:Laryngoscopy / Q000379:methods*; D009416:Nerve Regeneration / Q000502:physiology*; D011379:Prognosis; D011897:Random Allocation; D061226:Recurrent Laryngeal Nerve Injuries / Q000150:complications / Q000175:diagnosis*; D013997:Time Factors; D014826:Vocal Cord Paralysis / Q000175:diagnosis* / Q000209:etiology
keywords: Recurrent laryngeal nerve; electromyography; vocal cord paralysis