Stellan Hertegård

Cross-linked hyaluronan used as augmentation substance for treatment of glottal insufficiency: Safety aspects and vocal fold function

Objective To examine safety aspects and vocal fold function after vocal fold augmentation with a cross‐linked hyaluronan derivative (hylan B gel) as compared with bovine collagen.

Vocal Fold Vibrations: High-Speed Imaging, Kymography, and Acoustic Analysis: A Preliminary Report †

Objectives To evaluate a new analysis system, High‐Speed Tool Box (H. Larsson, custom‐made program for image analysis, version 1.1, Department of Logopedics and Phoniatrics, Huddinge University Hospital, Huddinge, Sweden, 1998) for studying vocal fold vibrations using a high‐speed camera and to relate findings from these analyses to sound characteristics.

Viscoelastic and Histologic Properties in Scarred Rabbit Vocal Folds After Mesenchymal Stem Cell Injection

Objective/Hypothesis: The aim of this study was to analyze the short‐term viscoelastic and histologic properties of scarred rabbit vocal folds after injection of human mesenchymal stem cells (MSC) as well as the degree of MSC survival. Because MSCs are antiinflammatory and regenerate mesenchymal tissues, can MSC injection reduce vocal fold scarring after injury?

Glottal closure, transglottal airflow, and voice quality in healthy middle-aged women

Seventeen healthy women, 45 to 61 years old, were examined using videofiberstroboscopy during phonation at three loudness levels. Two phoniatricians evaluated glottal closure using category and ratio scales. Transglottal airflow was studied by inverse filtering of the oral airflow signal recorded in a flow mask (Glottal Enterprises System) during the spoken phrase /ba:pa:pa:pa:p/ at three loudness levels. Subglottal pressure was estimated from the intraoral pressure during p occlusion. Running speech and the repeated /pa:/ syllables were perceptually evaluated by three speech pathologists regarding breathiness, hypo-, and hyperfunction, using continuous scales. Incomplete glottal closure was found in 35 of 46 phonations (76%). The degree of glottal closure increased significantly with raised loudness. Half of the women closed the glottis completely during loud phonation. Posterior glottal chink (PGC) was the most common gap configuration and was found in 28 of 46 phonations (61%). One third of the PGCs were in the cartilaginous glottis (PGCc) only. Two thirds extended into the membranous portion (PGCm); most of these occurred during soft phonation. Peak flow, peak-to-peak (AC) flow, and the maximum rate of change for the flow in the closing phase increased significantly with raised loudness. Minimum flow decreased significantly from normal to loud voice. Breathiness decreased with increased loudness. The results suggest that the incomplete closure patterns PGCc and PGCm during soft phonation ought primarily to be regarded as normal for Swedish women in this age group.

Cross-linked hyaluronan versus collagen for injection treatment of glottal insufficiency : 2-year follow-up.

Objectives—To evaluate the long-term (24 months) clinical performance (vocal fold function) and safety of hylan B gel as compared with bovine cross-linked collagen in the treatment of patients with glottal insufficiency. Material and Methods—In a prospective trial, 70 patients with glottal insufficiency due to unilateral vocal fold paresis (n=35) or atrophy (n=35) were randomized to received either hylan B gel (n=47) or collagen (n=23) injections into 1 vocal fold. Forty-two of the patients were examined 24 months after treatment. Evaluations were made based on patients’ subjective ratings, digitized videostroboscopic measurements, maximum phonation time and phonation quotient. Results—The patients’ self-ratings were significantly improved in both the hylan B gel and collagen groups. Videostroboscopic measurements of glottal closure were significantly improved for both groups. The hylan B gel group showed a trend towards less resorption at the injected vocal fold edge in comparison with the collagen group (p=0.05). No serious adverse events were observed. Twenty-eight patients dropped out of the study after 12 months: 18 had been re-injected or operated on with medialization laryngoplasty due to insufficient voice and 10 had either died of causes unrelated to the study or refused to attend follow-up. Conclusions—No long-term side-effects were found for either the hylan B gel or collagen groups after injection treatment. Both treatments resulted in significantly improved voice as rated by the patients and significantly improved glottal closure. Some resorption was noted for both substances, and ≈25% of the patients chose re-treatment 2 years after the initial treatment.

A comparison of subglottal and intraoral pressure measurements during phonation

Intraoral pressure and subglottal pressure, derived from tracheal puncture, were recorded with the electroglottographic signal for one normal speaking male during phonation. The mean subglottal pressure for vowels was also estimated by interpolating the intraoral pressure from surrounding /p/occlusions. The pressure measurements were highly correlated (r = 0.98) and there were small pressure value differences (on average < 2%). The effects of varying speech rate and mode of phonation on the pressure measurements are discussed. A decrease in pressure from the mean subglottal pressure for the open phase and an increase for the closed phase was found during the glottal vibratory cycles.

Botulinum toxin injections for essential voice tremor.

Fifteen patients, 13 women and 2 men, with a mean age of 72.7 years (56 to 86 years) and a clinical diagnosis of essential voice tremor, were treated with botulinum injections to the thyroarytenoid muscles, and in some cases, to the cricothyroid or thyrohyoid muscles. Evaluations were based on subjective judgments by the patients, and on perceptual and acoustic analysis of voice recordings. Subjective evaluations indicated that the treatment had a beneficial effect in 67% of the patients. Perceptual evaluations showed a significant decrease in voice tremor during connected speech (p < .05). Acoustic analysis showed a nearly significant decrease in the fundamental frequency variations (p = .06) and a significant decrease in fundamental frequency during sustained vowel phonation (p < .01). The results of perceptual evaluation coincided most closely with the subjective judgments. It was concluded that the treatment was successful in 50% to 65% of the patients, depending on the method of evaluation.

Viscoelastic properties of rabbit vocal folds after augmentation.

BACKGROUND: Vocal fold function is closely related to tissue viscoelasticity. Augmentation substances may alter the viscoelastic properties of vocal fold tissues and hence their vibratory capacity. OBJECTIVES: We sought to investigate the viscoelastic properties of rabbit vocal folds in vitro after injections of various augmentation substances. STUDY DESIGN AND SETTING: Polytetrafluoroethylene (Teflon), cross-linked collagen (Zyplast), and cross-linked hyaluronan, hylan b gel (Hylaform) were injected into the lamina propria and the thyroarytenoid muscle of rabbit vocal folds. Dynamic viscosity of the injected vocal fold as a function of frequency was measured with a Bohlin parallelplate rheometer during small-amplitude oscillation. RESULTS: All injected vocal folds showed a decreasing dynamic viscosity with increasing frequency. Vocal fold samples injected with hylan b gel showed the lowest dynamic viscosity, quite close to noninjected control samples. Vocal folds injected with polytetrafluoroethylene showed the highest dynamic viscosity followed by the collagen samples. CONCLUSIONS: The data indicated that hylan b gel in short-term renders the most natural viscoelastic properties to the vocal fold among the substances tested. This is of importance to restore/preserve the vibratory capacity of the vocal folds when glottal insufficiency is treated with injections.

Simultaneous analysis of vocal fold vibration and transglottal airflow: exploring a new experimental setup.

The purpose of this study was to develop an analysis system for studying the relationship between vocal fold vibration and the associated transglottal airflow. Recordings of airflow, electroglottography (EGG), oral air pressure, and acoustic signals were performed simultaneously with high-speed imaging at a rate of approximately 1900 frames/s. Inverse filtered airflow is compared with the simultaneous glottal area extracted from the high-speed image sequence. The accuracy of the synchronization between the camera images and the foot pedal synchronization pulse was examined, showing that potential synchronization errors increase with time distance to the synchronization pulse. Therefore, analysis was limited to material near the synchronization pulse. Results corroborate previous predictions that air flow lags behind area, but also they reveal that relationships between these two entities may be complex and apparently varying with phonation mode.

Injection of Embryonic Stem Cells Into Scarred Rabbit Vocal Folds Enhances Healing and Improves Viscoelasticity: Short-Term Results†

Objectives: Scarring caused by trauma, postcancer treatment, or inflammation in the vocal folds is associated with stiffness of the lamina propria and results in severe voice problems. Currently there is no effective treatment. Human embryonic stem cells (hESC) have been recognized as providing a potential resource for cell transplantations, but in the undifferentiated state, they are generally not considered for therapeutic use due to risk of inadvertent development. This study assesses the functional potential of hESC to prevent or diminish scarring and improve viscoelasticity following grafting into scarred rabbit vocal folds.