title: Effects of asymmetric superior laryngeal nerve stimulation on glottic posture, acoustics, vibration.
abstract: OBJECTIVE
  Evaluate the effects of asymmetric superior laryngeal nerve stimulation on the vibratory phase, laryngeal posture, and acoustics.
  
  
  METHODS
  Basic science study using an in vivo canine model.
  
  
  METHODS
  The superior laryngeal nerves were symmetrically and asymmetrically stimulated over eight activation levels to mimic laryngeal asymmetries representing various levels of superior laryngeal nerve paresis and paralysis conditions. Glottal posture change, vocal fold speed, and vibration of these 64 distinct laryngeal-activation conditions were evaluated by high speed video and concurrent acoustic and aerodynamic recordings. Assessments were made at phonation onset.
  
  
  RESULTS
  Vibratory phase was symmetric in all symmetric activation conditions, but consistent phase asymmetry toward the vocal fold with higher superior laryngeal-nerve activation was observed. Superior laryngeal nerve paresis and paralysis conditions had reduced vocal fold strain and fundamental frequency. Superior laryngeal nerve activation increased vocal fold closure speed, but this effect was more pronounced for the ipsilateral vocal fold. Increasing asymmetry led to aperiodic and chaotic vibration.
  
  
  CONCLUSIONS
  This study directly links vocal-fold tension asymmetry with vibratory phase asymmetry, in particular the side with greater tension leads in the opening phase. The clinical observations of vocal fold lag, reduced vocal range, and aperiodic voice in superior laryngeal paresis and paralysis is also supported.
authors.affiliation: Department of Head and Neck Surgery, Laryngeal Physiology Laboratory, CHS 62-132, Los Angeles, California, U.S.A.
authors.forename: Dinesh K
authors.initials: DK
authors.lastname: Chhetri
authors.forename: Juergen
authors.initials: J
authors.lastname: Neubauer
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Bergeron
authors.forename: Elazar
authors.initials: E
authors.lastname: Sofer
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Peng
authors.forename: Nausheen
authors.initials: N
authors.lastname: Jamal
mesh_terms: D000162:Acoustics; D000818:Animals; D004285:Dogs; D004599:Electric Stimulation Therapy / Q000379:methods*; D005931:Glottis / Q000502:physiology*; D007823:Laryngeal Nerves / Q000503:physiopathology*; D007830:Larynx / Q000502:physiology*; D010699:Phonation; D014732:Vibration; D014741:Video Recording; D014827:Vocal Cords / Q000502:physiology*
keywords: Superior laryngeal nerve; acoustics; high speed video; laryngeal asymmetry; vibration; voice production