Comparative histochemical aspects of mammalian thyroarytenoid musculature.

A survey is given of histological and histochemical aspects of mammalian thyroarytenoid musculature of several animal species. Purpose of the study is to find out in what respect the possibility of differentiated and prolonged sound production can be found back in the histological and histochemical properties of mammalian thyroarytenoid musculature. The findings are compared to the results of previous studies of thyroarytenoid musculature in man (Kersing and Jennekens, 2004). The presence of type I fibres seems to be crucial.

Accuracy of measurements on digital videostroboscopic images of the vocal folds.

OBJECTIVES: The reliability of objective measurements on digital laryngeal images was investigated. METHODS: The magnitude of the error of measurement of surface areas by visually tracing the outline was determined for three different areas: the area of the lesion and, during vibration, the glottal area on maximal opening of the vocal folds and the glottal area on maximal closing of the vocal folds. RESULTS: The errors in these areas were 10% to 30%. The results suggest that the error is mainly due to the uncertainty of the real outline of areas with a vague boundary. Correction for differences in magnification between two images (posttherapy and pretherapy) is of importance in about 25% to 65% of cases, depending on the area measured. CONCLUSIONS: Only when the magnification ratio is small (less than about +/- 10% from 1.0) may a correction not be necessary.

Effects of voice therapy as objectively evaluated by digitized laryngeal stroboscopic imaging.

Objective measurements derived from digitized laryngeal stroboscopic images were used to demonstrate changes in vocal fold vibration and in the size of benign lesions after 3 months of voice therapy. Forty chronically dysphonic patients were studied. By means of a rigid stroboscope, pretreatment and posttreatment recordings were made of the vocal folds at rest and under stroboscopic light during phonation. From each recording, images of the positions at rest and during vibration at maximal opening and at maximal closure were digitized. The surface areas of any lesions and of the glottal gap were independently measured in the digitized images by 2 experienced laryngologists. Referential distances were determined in order to compensate for discrepancies in magnification in the various recordings. After 3 months of voice therapy, significant improvement in lesion size and degree of maximal closure during vibration could be demonstrated in about 50% of the patients. The degree of maximal opening did not prove to be a significant parameter.

Laryngeal and vocal changes during vagus nerve stimulation in epileptic patients.

Left vagus nerve stimulation (VNS) by means of an implanted electrode has proven to reduce seizure frequency in epileptic patients with medically refractory seizures. This technique is now widely applied over the world. Voice changes appear to be one of the major side effects. The morphodynamic changes in the larynx and the acoustic impacts have been analyzed in detail in 7 implanted patients. Basic vagus stimulation is well tolerated. Extra stimulation induces an adductory spasm of either the ipsilateral vocal fold or the vestibular fold. The result, when the patient phonates, consists of a slight increase of F0 as well as a moderate increase of random period perturbation, but there is no evidence for the occurrence of "bifurcations." Further, as the glottic closure remains sufficient, there is no increase in turbulent noise. The lack of increase in turbulent noise and the lack of "bifurcations" appears to clearly differentiate a spasmodic contraction of the vocal cord from a unilateral vocal fold paralysis.