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PubMed2007

[Influence of thyroid cartilage ossification in laryngeal ultrasound].

BACKGROUND: Topological features of the larynx and hypopharynx may be depicted during sonographic examination of the neck, although ultrasound is seen of minor diagnostic importance. The varying extend of thyroid cartilage ossification appears to be the major limiting factor. We intended to assess the sonographic accessability of laryngeal structures with high end resolution ultrasound devices. METHODS AND PATIENTS: We examined 101 patients endoscopically and by ultrasound. Normal laryngeal findings and pathologies were examined and analysed considering limitations by thyroid cartilage ossification. RESULTS: Despite varying grades of ossification, the majority of laryngeal structures were clearly displayed by ultrasound. Ossification was increasing in the elderly. In 16 cases (16 %) ossification prevented a successful evaluation. In 9 cases of malignant tumor and one laryngocele sonographic assessment was able to contribute additional diagnostic information. CONCLUSIONS: Ultrasound of the larynx requires methodical experience of the operator but is capable to depict relevant anatomic structures, even with presence of thyroid cartilage ossification, thus being able to increase diagnostic impact and may save additional imaging modalities.

Adult↗
PubMed1994

A quantitative model of voice F0 control.

A mathematical model of the larynx, based on biomechanical principles, is described. Components represented include two cartilage elements (cricoid with locked arytenoids, and thyroid), three muscles (thyroarytenoid [TA], cricothyroid pars rectus [CTr], and cricothyroid pars oblique [CTo]), and two ligaments (cricothyroid and vocal ligaments), as well as subglottal pressure (PS). For any combination of muscle activities and PS level, equilibrium positions and tensions could be calculated for components in the system. The tensions and lengths of vocal fold elements were then used to calculate fundamental frequency (F0) of vocal fold vibration. Systematic variation of model muscle activation and PS patterns allowed study of the behavior of the model. TA activity tended to shorten the vocal folds; increased levels of CTr and CTo activity, and PS, had the opposite effect. Increased activity of any muscle tended to increase vocal fold tension, while PS increases were mainly ineffective. F0 was generally increased by increased CTr, CTo, and PS values. However, TA activity had a strongly nonmonotonic effect on F0. Best control of F0 could be achieved only by a process of co-contraction of all muscles at low frequencies, followed by sustained contraction of CTr and CTo with decreasing TA activity for F0's increasing above this low-frequency range. These results are discussed in terms of their possible implications for norma and abnormal voice production, and as a set of constraints for neural modeling efforts.

Biomechanical Phenomena↗