Study of movements of individual structures of the larynx during swallowing

Objective: The purpose of this study was to reveal movements of individual structures of the larynx during swallovving. Methods: Subjects were 7 healt hy adults, aged 24 to 32 years (average 27 years), who had no organic or fu nctional disease of the pharynx and larynx and 2 adults with unilateral rec urrent nerve palsy, aged 49 and 60 years, respectively. We used the Toshiba IIDR system, which is composed of an X-ray TV system and a digital image m anaging circuit. One-fifth diluted Omnipark 300 was used as contrast medium (lohexol), with 15 cc for each swallow. The mask image for subtraction was designated as the frame before laryngeal elevation during swallowing for s ubtraction. We obtained the images for observation and analysis after subtr acting the mask image from continuously obtained images. These images were captured into a personal computer at 30 frames per s and thereafter frame-b y-frame observation and analysis were performed by means of NIH image 1.56. Results: We observed that the vocal folds underwent a series of movements during swallowing. (1) They adduct slowly and do not ascend; (2) then begin to ascend and continue adducting, whereby (3) they abduct for a moment whi le ascending. (4) Again, they adduct and achieve closure. (5) While maintai ning closure, vocal folds elevate further to reach their maximal elevation; and (6) begin to abduct rapidly while maintaining maximal elevation. Final ly, (7) they begin to descend and undergo repeated irregular abduction and adduction while descending. In examining the relationship between closure a nd opening at levels of the vocal fold and false vocal fold, we found that closure at the false vocal fold level precedes that at the vocal fold level and that opening at the vocal fold level precedes that at the level of the false vocal fold. Conclusion: Closure of the false vocal fold level appear s important in the protection of the lower respiratory tract during swallow ing. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.