Bruce R. Gerratt

Cinegraphic observations of laryngeal function in parkinson's disease†‡

Thirty‐two unselected male patients with Parkinsons disease were examined by telescopic cinelaryngoscopy. Correlation of vocal abnormality and general neurologic symptoms with the laryngoscopic examination leads to the conclusion that the phonatory abnormalities noted in Parkinsons disease are related to rigidity in the phonatory posture of the larynx. The described dysfunctions correlated with the symmetry of trunk and limb rigidity in 100% of the patients.

Laryngeal modeling: theoretical, in vitro, in vivo.

Because the larynx is situated anatomically in an area which is difficult to measure and visualize, theoretical, in vitro, and in vivo models are used in laryngeal research. Vocal fold vibration was studied in anesthetized dogs, while electrically stimulating independently the superior and recurrent laryngeal nerves under conditions of constant airflow. Photoglottographic (PGG), electroglottographic (EGG), and subglottic pressure signals were obtained while stroboscopically photographing the larynx. Specific points along PGG, EGG, and subglottic pressure waveforms were correlated with laryngeal events which occurred during vibration. The canine larynx, in an experimentally produced phonatory mode, vibrates in a two mass (upper and lower margin) system and appears comparable to modal human voice production. The recorded glottogrophic waveforms from experimentally produced phonation in the canine are similar to signals recorded from humans. However, observed differences can be related to anatomic differences.

Measuring vocal quality with speech synthesis

Much previous research has demonstrated that listeners do not agree well when using traditional rating scales to measure pathological voice quality. Although these findings may indicate that listeners are inherently unable to agree in their perception of such complex auditory stimuli, another explanation implicates the particular measurement method-rating scale judgments-as the culprit. An alternative method of assessing quality-listener-mediated analysis-synthesis-was devised to assess this possibility. In this new approach, listeners explicitly compare synthetic and natural voice samples, and adjust speech synthesizer parameters to create auditory matches to voice stimuli. This method is designed to replace unstable internal standards for qualities like breathiness and roughness with externally presented stimuli, to overcome major hypothetical sources of disagreement in rating scale judgments. In a preliminary test of the reliability of this method, listeners were asked to adjust the signal-to-noise ratio for 12 synthetic pathological voices so that the resulting stimuli matched the natural target voices as well as possible For comparison to the synthesis judgments, listeners also judged the noisiness of the natural stimuli in a separate task using a traditional visual-analog rating scale. For 9 of the 12 voices, agreement among listeners was significantly (and substantially) greater for the synthesis task than for the rating scale task. Response variances for the two tasks did not differ for the remaining three voices. However, a second experiment showed that the synthesis settings that listeners selected for these three voices were within a difference limen, and therefore observed differences were perceptually insignificant. These results indicate that listeners can in fact agree in their perceptual assessments of voice quality, and that analysis-synthesis can measure perception reliably.

Selective Laryngeal Adductor Denervationreinnervation: A New Surgical Treatment for Adductor Spasmodic Dysphonia

During the past decade, botulinum toxin (Botox) has emerged as the accepted treatment for adductor spasmodic dysphonia (ASD). This therapy, which produces bilateral weakness of the thyroarytenoid muscle, undoubtedly produces physiologic effects that are beneficial to patients with ASD. However, it also has important limitations, including the need for repeated injections, the unpredictable relationship between dosage and response, and the possibility of short-term swallowing and voice problems. In this study, we will report our preliminary experience with a new surgical treatment for ASD. In this new procedure, the adductor branch of the recurrent laryngeal nerve is selectively denervated bilaterally, and its distal nerve stumps are reinnervated with branches of the ansa cervicalis nerve. Each of the patients was followed for at least 12 months; the median follow-up is 36 months. The outcome of the operation in 21 consecutive patients is reported. Nineteen of the 21 patients were judged to have an overall severity of dysphonia that was “absent to mild” following the procedure. Only 1 patient underwent further treatment with Botox postoperatively. The implications of this new procedure for ASD are discussed.

The perceptual structure of pathologic voice quality

Although perceptual assessment is included in most protocols for evaluating pathologic voices, a standard set of valid scales for measuring voice quality has never been established. Standardization is important for theory and for clinical acceptance, and also because validation of objective measures of voice depends on valid perceptual measures. The present study used large sets (n = 80) of male and female voices, representing a broad range of diagnoses and vocal severities. Eight experts judged the dissimilarity of each pair of voices, and responses were analyzed using nonmetric individual differences multidimensional scaling. Results indicate that differences between listeners in perceptual strategy are so great that the fundamental assumption of a common perceptual space must be questioned. Because standardization depends on the assumption that listeners are similar, it is concluded that efforts to standardize perceptual labels for voice quality are unlikely to succeed. However, analysis by synthesis may provide an alternate means of modeling quality as a function of both voices and listeners, thus avoiding this problem.

Measurement of Young's Modulus in the in Vivo Human Vocal Folds:

Currently, surgeons have no objective means to evaluate and optimize results of phonosurgery intraoperatively. Instead, they usually judge the vocal folds subjectively by visual inspection or by listening to the voice. This paper describes a new device that measures Youngs (elastic) modulus values for the human vocal fold intraoperatively. Physiologically, the modulus of the vocal fold may be important in determining the nature of vocal fold vibration in normal and pathologic states. This study also reports the effect of recurrent laryngeal nerve stimulation on Youngs modulus of the human vocal folds, measured by means of transcutaneous nerve stimulation techniques. Youngs modulus increased with increases in current stimulation to the recurrent laryngeal nerve. Ultimately, Youngs modulus values may assist surgeons in optimizing the results of various phonosurgeries.

Treatment of Parkinson Hypophonia With Percutaneous Collagen Augmentation

Objectives: It has been estimated that more than 70% of patients with Parkinson disease experience voice and speech disorders characterized by weak and breathy phonation, and dysarthria. This study reports on the efficacy of treating Parkinson patients who have glottal insufficiency.

Videostroboscopy of Human Vocal Fold Paralysis

Previous stroboscopic studies of human vocal cord paralysis have been infrequent and have lacked documentation of the site of lesion. In order to study human laryngeal paralysis, the recurrent and superior laryngeal nerves were infiltrated unilaterally with lidocaine hydrochloride in three human volunteers. Vagal paralysis was simulated by combined (superior and recurrent) infiltration in one volunteer. Additionally, 20 patients with untreated laryngeal paralysis were studied from the voice laboratory at UCLA. In addition to videostroboscopic analysis, photoglottography and electroglottography were performed and synchronized with the stroboscopic images. The most significant finding in stroboscopy of the paralyzed larynx was the asymmetry of traveling wave motion. The traveling wave on the normal vocal fold had a faster wave velocity that created a phase difference in the vibration of the two folds. The wave also traversed a greater distance along the vocal fold mucosa on the normal side. No patient or volunteer with untreated laryngeal paralysis had a symmetric traveling wave, either in superior or recurrent laryngeal nerve paralysis. Synchronization with glottography indicated that the differentiated electroglottographic waveform provides useful information about the timing of glottic opening and closure in states of asymmetric laryngeal vibration. Implications for future studies and for the diagnosis of laryngeal paralysis are discussed.

Glottographic Measurement of Vocal Dysfunction A Preliminary Report

Objective measurement of vocal function is important in evaluating phonatory disorders, planning treatment, and documenting the effects of therapy. Glottographic measurement, ie, measures that describe glottal movement, can be performed and analyzed relatively easily, and can be related to the pathophysiology of vocal dysfunction. In our clinic, simultaneous recording of acoustic, photoglottographic and electroglottographic signals is being used in the evaluation of patients with voice disorders associated with neurologic impairments. Our experience with these measures indicates that they may provide detailed information about the vibratory patterns of the vocal folds, which appears to differentiate some phonatory characteristics among patients with differing types of disorders.

Glottographic measures of vocal fold vibration: an examination of laryngeal paralysis.

Photoglottography and electroglottography were applied to groups of patients with recurrent laryngeal nerve paralysis, superior laryngeal nerve paralysis, and combined recurrent and superior laryngeal nerve paralyses of idiopathic causes. Individual patients with resection of the vagal nerve above the origin of the superior laryngeal nerve were also studied. Open Quotient and Speed Quotient were calculated from the photoglottography signals. Speed Quotient values significantly differentiated recurrent laryngeal nerve paralysis from idiopathic paralysis and superior laryngeal nerve paralysis, as well as from normal function. Data from patients with vagal resection clearly differentiated them from patients with recurrent laryngeal nerve paralysis. The measure of Open Quotient distinguished pathological phonation from normal, but was not as useful for separation of differing lesions. Electroglottography appeared to be less useful than photoglottography. The pathophysiology underlying the observed glottographic signals is discussed.