title: Mechanism of glottic closure in a model of unilateral vocal fold palsy.
abstract: The effect of extrinsic laryngeal muscles on the position of the paralyzed vocal fold (VF) was analyzed in 13 adult human larynges. Fresh specimens were suspended within a specially constructed frame designed to reproduce the three-dimensional position of the VF, and to allow for simulation of laryngeal muscle action, in five successive experiments resembling: 1) complete vagal paralysis and contralateral adduction, 2) laryngeal elevation added, 3) vocal fold stretching added, 4) contralateral laryngeal tilting added, and 5) ipsilateral cricothyroid muscle activation added. We observed an incremental narrowing of the middle and posterior glottic gaps from 3.9 mm and 6.8 mm respectively in experiment 1 to 1.1 mm and 1.9 mm in experiment 5. Glottic closure in the final experiment was associated with rotation of the glottis to the "paralyzed" side in the axial plane, and contralateral laryngeal tilting in the coronal plane. We show that extrinsic laryngeal muscles can help to close a paralytic gap; crossing of the contralateral VF past the midline was not observed in any of the experiments.
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Ain Shams University, Cairo, Egypt.
authors.forename: M A
authors.initials: MA
authors.lastname: Riad
authors.forename: M N
authors.initials: MN
authors.lastname: Kotby
mesh_terms: D000328:Adult; D005260:Female; D007839:Functional Laterality; D005931:Glottis / Q000503:physiopathology*; D006801:Humans; D007821:Laryngeal Muscles / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D014826:Vocal Cord Paralysis / Q000503:physiopathology*