Effect of Vocal Fold Injury Location on Vibratory Parameters in Excised Canine Larynges

Abstract

Objective To investigate the effect of vocal fold injury location on vibratory amplitude and lateral phase difference. Study design Repeated measures with each excised canine larynx serving as own control. Setting Basic science study conducted in university laboratory. Methods Vocal fold vibration of excised canine larynges was recorded with a high speed camera before and after inducing vocal fold injury at one of five locations: anterior, middle, posterior, medial, or superior. Medial and superior injuries were created within the middle third of the vocal fold. Five larynges were used for each of the five injury locations. Kymography was performed at the midpoint of the vocal folds for each video. Pre- and post-injury vibratory amplitude and lateral phase difference were compared for each location. Results The anterior and medial injuries produced consistent decreases in vibratory amplitude. Middle and posterior injuries may slightly decrease amplitude. Superior injuries seemed to have no effect on amplitude. Anterior and medial injuries induce phase asymmetry between the right and left vocal folds. Middle injuries appeared to affect phase difference slightly, whereas posterior and superior injuries had no effect. Conclusion Injury to the anterior or medial portions of the vocal fold may be most likely to cause abnormal vocal fold vibration. Using caution in these locations during phonosurgery may favor superior post-operative vocal outcomes.

Voice Outcome of Modified Frontolateral Partial Laryngectomy in Excised Canine Larynges and Finite Element Model

“…The finite element model results showed that FLPL model had a higher vibration amplitude (.838 mm) than in the normal fold (.684 mm), which was relieved with application of tension in the MFLPL model (.554 mm). Amplitude values were similar to our excised vocal fold observations, as well as results from previous studies 28,29 . While our model incorporated directly applied loads, which prevented us from analyzing the effect of elongation on frequency, the effect on amplitude corresponded with observations in the excised vocal folds.…”

“…Amplitude values were similar to our excised vocal fold observations, as well as results from previous studies. 28,29 While our model incorporated directly applied loads, which prevented us from analyzing the effect of elongation on frequency, the effect on amplitude corresponded with observations in the excised vocal folds.…”

Excised larynx evaluation of subthyroid cartilage approach to medialization thyroplasty

“…Mucosal wave amplitude was measured for each vocal fold and calculated as the average of the amplitudes of the upper and lower lips. Interfold and intrafold phase differences were calculated using the method described by Krausert et al, where a phase difference of π radians represents perfectly symmetric vibration, and a phase difference of zero radians represents perfectly asymmetric vibration.…”

Development of Excised Larynx

“…They found that the vibratory amplitude consistently decreased and vocal folds became asymmetric by anterior and medial injuries. 48 Tse et al removed the epithelium of the vocal fold from an excised human larynx, and then made it phonate in an excised larynx apparatus. They found that closed quotient decreased and that there was left-right vibration asymmetry.…”