Dinesh K Chhetri1, Juergen Neubauer, Elazar Sofer. 1. Laryngeal Physiology Laboratory, Department of Head and Neck Surgery, UCLA School of Medicine, Los Angeles, California, U.S.A.
Abstract
OBJECTIVES/HYPOTHESIS: Evaluate the influence of asymmetric recurrent laryngeal nerve (RLN) stimulation on the vibratory phase, acoustics and aerodynamics of phonation. STUDY DESIGN: Basic science study using an in vivo canine model. METHODS: The RLNs were symmetrically and asymmetrically stimulated over eight graded levels to test a range of vocal fold activation conditions from subtle paresis to paralysis. Vibratory phase, fundamental frequency (F0 ), subglottal pressure, and airflow were noted at phonation onset. The evaluations were repeated for three levels of symmetric superior laryngeal nerve (SLN) stimulation. RESULTS: Asymmetric laryngeal adductor activation from asymmetric left-right RLN stimulation led to a consistent pattern of vibratory phase asymmetry, with the more activated vocal fold leading in the opening phase of the glottal cycle and in mucosal wave amplitude. Vibratory amplitude asymmetry was also observed, with more lateral excursion of the glottis of the less activated side. Onset fundamental frequency was higher with asymmetric activation because the two RLNs were synergistic in decreasing F0 , glottal width, and strain. Phonation onset pressure increased and airflow decreased with symmetric RLN activation. CONCLUSION: Asymmetric laryngeal activation from RLN paresis and paralysis has consistent effects on vocal fold vibration, acoustics, and aerodynamics. This information may be useful in diagnosis and management of vocal fold paresis. LEVEL OF EVIDENCE: N/A.
OBJECTIVES/HYPOTHESIS: Evaluate the influence of asymmetric recurrent laryngeal nerve (RLN) stimulation on the vibratory phase, acoustics and aerodynamics of phonation. STUDY DESIGN: Basic science study using an in vivo canine model. METHODS: The RLNs were symmetrically and asymmetrically stimulated over eight graded levels to test a range of vocal fold activation conditions from subtle paresis to paralysis. Vibratory phase, fundamental frequency (F0 ), subglottal pressure, and airflow were noted at phonation onset. The evaluations were repeated for three levels of symmetric superior laryngeal nerve (SLN) stimulation. RESULTS: Asymmetric laryngeal adductor activation from asymmetric left-right RLN stimulation led to a consistent pattern of vibratory phase asymmetry, with the more activated vocal fold leading in the opening phase of the glottal cycle and in mucosal wave amplitude. Vibratory amplitude asymmetry was also observed, with more lateral excursion of the glottis of the less activated side. Onset fundamental frequency was higher with asymmetric activation because the two RLNs were synergistic in decreasing F0 , glottal width, and strain. Phonation onset pressure increased and airflow decreased with symmetric RLN activation. CONCLUSION: Asymmetric laryngeal activation from RLN paresis and paralysis has consistent effects on vocal fold vibration, acoustics, and aerodynamics. This information may be useful in diagnosis and management of vocal fold paresis. LEVEL OF EVIDENCE: N/A.
Authors: Dinesh K Chhetri; Juergen Neubauer; Jennifer L Bergeron; Elazar Sofer; Kevin A Peng; Nausheen Jamal Journal: Laryngoscope Date: 2013-08-05 Impact factor: 3.325
Authors: Nelson Roy; Michael E Barton; Marshall E Smith; Christopher Dromey; Ray M Merrill; Cara Sauder Journal: Laryngoscope Date: 2009-05 Impact factor: 3.325