title: Innervation of the cricothyroid muscle by the recurrent laryngeal nerve.
abstract: The recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (SLN) are generally thought to innervate the endolaryngeal muscles and the cricothyroid muscle (CTM), respectively. Meticulous anatomic studies found communication between these nerves (ie, the human communicating nerve). In this study, we report the innervation of the CTM by the RLN.
  
  
  
  We performed electromyographic studies of 50 patients during thyroidectomy (20 total and 30 hemithyroidectomies). During surgery, the external branch of the SLN, RLN, and vagus nerve were stimulated. Responses were evaluated by visual observation of the CTM and by electromyographies through needle electrodes inserted into the CTM.
  
  
  
  Seventy CTMs were evaluated. The RLN stimulation yielded both visible contractions and clear electromyographic responses (>300 µV) in 27 (39%), either response in 24 (34%), and neither response in 19 (27%) of the CTMs. The vagus stimulation gave similar results.
  
  
  
  The RLN innervated the CTM at least in 39% cases. © 2015 Wiley Periodicals, Inc. Head Neck 38: E441-E445, 2016.
authors.affiliation: Department of Surgery, Kuma Hospital, Kobe, Japan.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Masuoka
authors.affiliation: Department of Surgery, Kuma Hospital, Kobe, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Miyauchi
authors.affiliation: Department of Surgery, Kuma Hospital, Kobe, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Yabuta
authors.affiliation: Department of Surgery, Kuma Hospital, Kobe, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Fukushima
authors.affiliation: Department of Surgery, Kuma Hospital, Kobe, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Miya
mesh_terms: D000328:Adult; D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D007821:Laryngeal Muscles / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D012009:Recurrent Laryngeal Nerve / Q000502:physiology*; D013965:Thyroidectomy; D055815:Young Adult
keywords: cricothyroid muscle; external branch of the superior laryngeal nerve (SLN); human communicating nerve; recurrent laryngeal nerve (RLN); voice impairment