title: Three-dimensional posture changes of the vocal fold from paired intrinsic laryngeal muscles.
abstract: Although the geometry of the vocal fold medial surface affects voice quality and is critical in the treatment of glottic insufficiency, the prephonatory shape of the vocal fold medial surface is not well understood. In this study, we activated intrinsic laryngeal muscles individually and in combinations, and recorded the temporal sequence and precise three-dimensional configurational changes of the vocal fold medial surface.
  
  
  
  In vivo canine hemilarynx model.
  
  
  
  A hemilaryngectomy was performed in an in vivo canine model and ink was used to mark the medial surface of the in situ vocal fold in a grid-like fashion. The thyroarytenoid (TA), lateral cricoarytenoid (LCA), cricothyroid (CT), and posterior cricoarytenoid (PCA) muscles were stimulated individually and in combinations. A right-angle prism whose hypotenuse formed the glottal midline provided two distinct views of the medial surface for a high-speed digital camera. Image-processing package DaVis (LaVision Inc., Goettingen, Germany) allowed time series cross-correlation analysis for three-dimensional deformation calculations of the vocal fold medial surface.
  
  
  
  Combined TA and LCA activation yields an evenly adducted rectangular glottal surface. Addition of thyroarytenoid to cricoarytenoid adducts the vocal fold from inferior to superior in a graded fashion allowing formation of a divergent glottis. Posterior cricoarytenoid has a bimodal relationship with thyroarytenoid favoring abduction. Cricothyroid and lateral cricoarytenoid yield unique glottal postures necessary but likely not conducive for efficient phonation.
  
  
  
  Understanding the three-dimensional geometry of the vocal fold medial surface will help us better understand the cause-effect relationship between laryngeal physiology and phonation.
  
  
  
  NA Laryngoscope, 127:656-664, 2017.
authors.affiliation: Department of Head and Neck Surgery, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, U.S.A.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Vahabzadeh-Hagh
authors.affiliation: Department of Head and Neck Surgery, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, U.S.A.
authors.forename: Zhaoyan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Head and Neck Surgery, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, U.S.A.
authors.forename: Dinesh K
authors.initials: DK
authors.lastname: Chhetri
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D004285:Dogs; D004558:Electric Stimulation / Q000379:methods; D005931:Glottis / Q000294:innervation / Q000502:physiology; D007821:Laryngeal Muscles / Q000294:innervation / Q000502:physiology*; D007825:Laryngectomy / Q000379:methods*; D010699:Phonation / Q000502:physiology*; D011187:Posture; D011897:Random Allocation; D014827:Vocal Cords / Q000502:physiology*; D014833:Voice Quality
keywords: Larynx; canine; intrinsic laryngeal muscle; pre-phonatory posture; vocal fold; voice