Neuroanatomical model for laryngeal operation

The focus of this presentation is on the development of a neuroanatomical model underlying laryngeal function. It is suggested that the model can be used as an aid to the understanding of the structures that support phonatory output as well as a basis for physiological research on the nature of voice production. Although the postulates are anatomically grounded, the approach utilized also shows that there is ongoing feedback during phonation and, hence, that both the motor and sensory (neural) networks are coordinated during any phonatory activity. Additionally, the discussion serves to review the neuroanatomical interface between respiration and voice.     

Treatment of laryngeal contact ulcers and granulomas: A 12-year retrospective analysis

Multiple etiological factors including gastroesophageal reflux, hyperfunctional voice use, and endotracheal intubation have been implicated in the development of posterior laryngeal ulcers and granulomas. The optimal approach to treatment of these lesions remains controversial. The mainstay of treatment at Vancouver General Hospital has been aggressive medical management of gastroesophageal reflux, with complimentary voice therapy offered to patients suspected of having significant hyperfunctional phonation. The authors reserve Botulinum toxin injection or surgical excision for patients who fail initial therapy. They conducted a retrospective analysis of their voice clinic records from 1985–1997 to examine the efficacy of this approach. They identified 76 patients with the diagnosis of contact ulcer or granuloma. Fifty-two patients had follow-up data available for review. Ninety-four percent of patients were treated nonsurgically: 35 patients were treated solely by dietary and medical therapy to control gastroesphageal reflux, 10 patients were treated by a combination of medical gastroesophageal reflux control and voice therapy, 3 patients had Botox injections, 2 patients had surgical excision of granuloma, 1 patient had a Kenalog injection, and 1 patient underwent laparoscopic fundoplication. Overall, 77% of patients had complete resolution, whereas 11% had partial resolution and another 11% had no significant improvement. The data supports control of gastroesophageal reflux as a central component in treatment of posterior laryngeal ulcers and granulomas.     

Resonant Voice: Spectral and Nasendoscopic Analysis

Although resonant voice therapy is a widely used therapeutic approach, little is known about what characterizes resonant voice and how it is physiologically produced. The purpose of this study was to test the hypothesis that resonant voice is produced by narrowing the laryngeal vestibule and is characterized by first formant tuning and more ample harmonics. Videonasendoscopic recordings of the laryngeal vestibule were made during nonresonant and resonant productions of /i/ in six subjects. Spectrums of the two voice types were also obtained. Spectral analysis showed that first formant tuning was exhibited during resonant voice productions and that the degree of harmonic enhancement in the range of 2.0 to 3.5 kHz was related to voice quality: nonresonant voice had the least amount of energy in this range, whereas a resonant-relaxed voice had more energy, and a resonant-bright voice had the greatest amount of energy. Visual-perceptual judgments of the videoendoscopic data indicated that laryngeal vestibule constriction was not consistently associated with resonant voice production.     

Combined-modality treatment of adductor spasmodic dysphonia with botulinum toxin and voice therapy

A combined-modality treatment program consisting of botulinum toxin injection (Botox) and voice therapy was used to treat 17 subjects diagnosed with adductor spasmodic dysphonia (ADD SD). Ten subjects with ADD SD served as the control and were given Botox only. Voice therapy after Botox injection was directed toward reducing the hyperfunctional vocal behaviors, primarily glottal overpressure at voice onset and anterior-posterior squeezing. The results indicated that subjects who underwent combined-modality treatment maintained significantly higher mean airflow rates for significantly longer periods. Moreover, there was a carryover effect in these patients when they received Botox only. Adductor spasmodic dysphonia is treated most effectively when intrinsic laryngeal muscle spasms are reduced or eliminated by Botox injection and extrinsic hyperfunctional vocal behaviors are treated with voice therapy     

Extrinsic Laryngeal Muscular Tension in Patients with Voice Disorders

The objective of this study was to establish a standard clinical evaluation tool for assessment by palpation of extrinsic laryngeal muscular tension (ELMT) and investigate the relationship between ELMT and different voice disorder diagnosis categories, particularly muscle misuse dysphonia (MMD), and the presence or absence of gastroesophageal reflux (GER). A palpation technique and tension grading system for four separate muscle groups (suprahyoid, thyrohyoid, cricothyroid, and pharyngolaryngeal) were established. 465 patients, 65% female and 35% male, were assessed sequentially and ELMT results were analyzed in relation to diagnosis and reflux status. A strong relationship was found between thyrohyoid muscle tension and both GER and MMD (p < or = 0.01). Thyrohyoid muscle tension is the only group that demonstrated a significant relationship with MMD. No significant difference in the ELMT scores was found between GER and non-GER patients, although a possible causal relationship was found between MMD type 3 and reflux. It is postulated that palpation of extrinsic laryngeal muscles can yield important information about internal laryngeal postures and diagnosis of muscle misuse voice disorders, particularly MMD type 3 (anteroposterior supraglottic compression). Integration of this technique into routine laryngeal examination can be a significant aid to diagnostic accuracy.     

Voice research: So What? A clearer view of voice production, 25 years of progress; the speaking voice

The past 25 years has yielded an impressive growth in our knowledge of vocal function. Interdisciplinary research cooperation in areas of laryngeal histology, vocal aerodynamics and acoustics, vocal fold vibratory characteristics, neurolaryngology, and phonatory models has led to a clearer view of voice production. This article offers a brief review of the progress that has been made in our understanding of the speaking voice and relates this knowledge to clinical practice. The importance of utilizing voice research to confirm traditional management techniques and to develop new physiologically based management approaches is also stressed.     

Traumatic vocal fold avulsion injury in a newborn

A full-term newborn developed respiratory compromise in the immediate postparturition period requiring urgent intubation. Evaluation of post-extubation stridor later the same day revealed an avulsion injury extending from the left vocal fold into the lateral glottic musculature. Primary repair was accomplished with anatomic realignment of the torn vocal fold and muscle. Endotracheal intubation was utilized for stenting and the patient was extubated following 3 days of paralysis with sedation. Follow-up examination revealed a reparative granuloma, which was lasered. Eight-week follow-up examination revealed normal vocal fold architecture. At 18 months the patient continues to have a normal voice and normal laryngeal development.     

Aerodynamic measurements of patients with parkinson''s disease

Patients with Parkinson's disease commonly complain of voice dysfunction. Most of these complaints can be attributed to the known muscular control disorders that occur with Parkinson's disease. However, the manifestations of Parkinson's disease muscular dysfunction on parameters of phonation such as airflow, laryngeal resistance, and subglottal pressure necessary to sustain phonation have not been reported. The purpose of this study was to examine the aerodynamic characteristics of flow, laryngeal resistance, and phonation pressure threshold in a heterogeneous population of patients with Parkinson's disease who had varying voice complaints and to compare the data to similar studies for human subjects who have no voice complaints. The studies used a noninvasive method of detecting flow and acoustic signal from the lips, oral cavity and nose during phonation and used an external flow interruption technique to estimate subglottal pressure and phonation threshold pressure. About one third of the patients could not produce phonation at regular and loud intensities that were comfortable for normal subjects. The mean subglottal pressure (SGP) of patients with Parkinson disease who could produce 3 levels of intensity comparable to normal subjects was significantly higher than the mean SG-Ps for normal subjects for the same intensities of vocal production. The mean flow rates measured from patients with Parkinson's disease at the same 3 intensities of phonation was not significantly greater than in normal subjects. This indicated that the mean laryngeal resistance calculated for patients with Parkinson's disease was notably and significantly greater than mean laryngeal resistance calculated for normal subjects at the same intensity levels. The mean vocal efficiency (VE) for normal subjects was not significantly different than the mean VE for patients with Parkinson's disease, because greater pressure was used to generate similar flow and acoustic energy. These findings correlate with the perception of patients with Parkinson's disease that they are working harder to produce phonation. The observation of notably greater laryngeal resistance and phonation threshold pressure in patients with Parkinson's disease suggests that further studies of the glottic aperture in patients with Parkinson' disease may be useful for understanding how this common motor disorder disturbs phonation.     

Physiological mechanisms of vocal frequency control: The role of tension

Control of fundamental frequency by the human voice may be accomplished using a variety of physiological mechanisms. Most of these mechanisms are myoelastic and include the length, mass, and longitudinal tension of the vocal folds. In this paper, a review of some of the data concerning the mechanisms for the creation of tension in the vocal folds is presented. The physiological mechanisms for the development of passive tension are reviewed and the potential contribution of passive tension in the control of fundamental frequency is discussed. Some of the mechanisms for the development of active muscle tension are described and the biomechanical characteristics of muscle are considered in the effort to explain the physiological control of fundamental frequency in the human voice     

“Compensatory falsetto”: Effects on vocal quality

The term “compensatory falsetto”, for the purpose of this investigation, refers to the development of an abnormally high-pitched voice in the presence of laryngeal pathology where more socially acceptable lower pitched voice production is possible. The purpose of this investigation was to compare laryngeal compensations and their effects on objective measures of vocal function during production of compensatory falsetto voice. Eighteen patients with abnormally high-pitched voice in the presence of underlying laryngeal pathology were evaluated in the Department of Otolaryngology at the University of Miami School of Medicine from January 1988 through December 1992 and were diagnosed with “compensatory falsetto”. Vocal fold paralysis (n = 11) was the most common laryngeal pathology. Vibratory characteristics were evaluated through videostrobolaryngoscopic examination. Acoustic and aerodynamic parameters assessed included fundamental frequency, jitter rate, harmonic-to-noise ratio, glottal air flow, and maximum phonation time. Production of a higher-pitched voice appeared to improve glottic closure and decrease the amount of air loss during phonation. A corresponding increase in maximum phonation time and improvement in acoustic characteristics of jitter and harmonic-to-noise ratio was also observed.     

Stroboscopic and acoustic measures of inspiratory phonation

Inspiratory phonation (IP) is the production of voice as air is taken into the lungs. Although IP is promoted as a laryngeal assessment and voice treatment technique, it has been described quantitatively in very few speakers. This study quantified changes in laryngeal adduction, fundamental frequency, and intensity during IP relative to expiratory phonation (EP). We hypothesized that IP would increase laryngeal abduction and fundamental frequency. The experiment was a within-subjects, repeated measures design with each subject serving as her own control. Participants were 10 females (ages 19-50 years) who underwent simultaneous transoral videostrobolaryngoscopy and acoustic voice recording. We found that membranous vocal fold contact decreased significantly during IP relative to EP, while the trends for change of ventricular fold squeeze during IP varied across individuals. Vocal fundamental frequency increased significantly during IP relative to EP, but intensity did not vary consistently across conditions. Without teaching or coaching, changes that occurred during IP did not carry over to EP produced immediately following IP within the same respiratory cycle.     

Speech task effects on acoustic and aerodynamic measures of women with vocal nodules

Vowel prolongation is often used to evaluate disordered voice production. In light of previous findings showing that co-articulation has significant influence on laryngeal function measures, the practice of using prolonged vowels to represent a speech sample is questioned. To test whether disordered and normal voice during vowel production is generalizable to connected speech, three speaking tasks were investigated: sustained vowel prolongation, syllable repetition and reading. Statistical differences were found between these tasks for certain amplitude and time based laryngeal function measures for adult women with disordered and normal voice. However, for the specific measures which were statistically different, the actual numerical and perceptual differences may be quite small. From a clinical assessment standpoint, the choice of the speech task may not make an apparent difference in the objective evaluation of disordered voice.     

A physiological and acoustic study on voiced bilabial fricative /β:/ as a vocal exercise

The voiced bilabial fricative /β:/ has been used as a vocal exercise. The present study investigated the effects of the exercise on voice production and voice source. This study compared vowel phonation on the syllable /a:p/ with the production of the exercise and vowel phonation before and immediately after the exercise. The methods were (a) dual-channel electroglottography, from which the vertical laryngeal position was derived, (b) electromyography using surface electrodes, and (c) inverse filtering of the acoustic signal to obtain an estimate of the voice source. In the production of /β:/ as compared with vowel phonation in most of the cases, the vertical laryngeal position seemed to be higher, the muscular activity of the larynx lower, and the slope of the voice source spectrum steeper. In vowel phonation after the exercise, the muscular activity seemed to be lower in most cases, although the voice source remained unchanged. This seems to indicate improved vocal economy.     

Physiological differences between the trained and untrained speaking and singing voice

This study concerns the premier singing voice and its relationship to physiological aptitude. Research literature is reviewed that indicates that during singing the trained singer uses different physiological strategies in comparison with the untrained singer, and that the noted physiological differences (respiratory, laryngeal, articulatory) occur during singing only and not during speech. Further, a study was conducted that compared the ability of trained singers versus untrained individuals to (a) discriminate differences in self-generated air pressures and (b) produce and maintain a constant level of air pressure. No significant differences were found between the trained and untrained groups in their ability to discriminate and/or control breath pressure. Combined results of previous studies and present findings lead to the tentative conclusion that the excelled singer is not physiologically endowed and/or “gifted,” but rather has benefited from technical voice training     

Acquisition of detailed laryngeal flow measurements in geometrically realistic models

Characterization of laryngeal flow velocity fields is important to understanding vocal fold vibration and voice production. One common method for acquiring flow field data is particle image velocimetry (PIV). However, because using PIV with models that have curved surfaces is problematic due to optical distortion, experimental investigations of laryngeal airflow are typically performed using models with idealized geometries. In this paper a method for acquiring PIV data using models with realistic geometries is presented. Sample subglottal, intraglottal, and supraglottal PIV data are shown. Capabilities and limitations are discussed, and suggestions for future implementation are provided.     

Neural control of vocalization: Respiratory and emotional influences

Previous research has shown that a region of the midbrain, the periaqueductal gray matter (PAG), is critical for vocalization. In this review, we describe the results of previous investigations in which we sought to find out how PAG neurons integrate the activity and precise timing of respiratory, laryngeal, and oral muscle activity for natural-sounding vocalization using the technique of excitatory amino acid microinjections in cats. In these studies, all surgical procedures were carried out under deep anaesthesia. In the precollicular decerebrate cat two general types of vocalization, classified as voiced and unvoiced, could be evoked by exciting neurons in the lateral part of the intermediate part of the PAG. The patterns of evoked electromyographic activity were strikingly similar to previously reported patterns of human muscle activity. Coordinated patterns of activity were evoked with just-threshold excitation leading to the conclusion that patterned muscle activity corresponding to the major categories of voiced and voiceless sound production are represented in the PAG. In a parallel series of human and animal experiments, we also determined that the speech and vocalization respiratory patterns are integrated and coordinated with afferent signals related to lung volume. These data have led to the proposal of a new hypothesis for the neural control of vocalization: that the PAG is a crucial brain site for mammalian voice production, not only in the production of emotional or involuntary sounds, but also as a generator of specific respiratory and laryngeal motor patterns essential for human speech and song     

Genetics of Vocal Quality Characteristics in Monozygotic Twins: A Multiparameter Approach

The main purpose of this study was to determine the vocal quality characteristics among the 45 monozygotic cotwins (MT). As the performance of the voice is related to several genetically determined anatomical and physiological factors, the authors hypothesized that the vocal characteristics and the overall vocal quality by means of the Dysphonia Severity Index (DSI) will be identical in MT. An additional objective of this study was to determine whether sex and age influence vocal similarities in MT and to compare the voice characteristics of MT with the normative data of unrelated peers. As more environmental factors influence the aging of the voice, age-related differences were expected. No sex-related differences were expected. Subjective and objective assessment techniques determined the vocal quality. No significant differences were obtained, and most comparisons resulted in significant correlation coefficients. For the acoustic parameters jitter and shimmer only, no significant correlation coefficients could be obtained. It is clear that the perceptual voice characteristics, the laryngeal aerodynamic measurements of maximum phonation time (MPT), the vocal performances, and the overall vocal quality by means of the DSI are similar in MT. These vocal characteristics are not influenced either by the subjects' age or sex and are situated within the normative range of unrelated peers. To what extent other aspects (environment, anxiety, tension, etc) might play a role in the acoustical dimensions regarding frequency and amplitude perturbation, which were in the normal range, is a subject of further research.     

Pitch Matching Accuracy of Trained Singers, Untrained Subjects with Talented Singing Voices, and Untrained Subjects with Nontalented Singing Voices in Conditions of Varying Feedback

At a physiological level, the act of singing involves control and coordination of several systems involved in the production of sound, including respiration, phonation, resonance, and afferent systems used to monitor production. The ability to produce a melodious singing voice (eg, in tune with accurate pitch) is dependent on control over these motor and sensory systems. To test this position, trained singers and untrained subjects with and without expressed singing talent were asked to match pitches of target pure tones. The ability to match pitch reflected the ability to accurately integrate sensory perception with motor planning and execution. Pitch-matching accuracy was measured at the onset of phonation (prephonatory set) before external feedback could be utilized to adjust the voiced source, during phonation when external auditory feedback could be utilized, and during phonation when external auditory feedback was masked. Results revealed trained singers and untrained subjects with singing talent were no different in their pitch-matching abilities when measured before or after external feedback could be utilized. The untrained subjects with singing talent were also significantly more accurate than the trained singers when external auditory feedback was masked. Both groups were significantly more accurate than the untrained subjects without singing talent.     

Vocal Evaluation in Teachers With or Without Symptoms

The aim of this study was to perform voice evaluation in teachers with and without vocal symptoms, identifying etiologic factors of dysphonia, voice symptoms, vocal qualities, and laryngeal lesions. Eighty teachers were divided into two groups: GI (without or sporadic symptoms, 40) and GII (with frequent vocal symptoms, 40). They answered a specific questionnaire, and were subject to a perceptual vocal assessment (maximum phonation time, glottal attack, resonance, coordination of breathing and voicing, pitch, and loudness), GIRBAS scale, and to videolaryngoscopy. Females were predominant in both groups, and the age range was from 36 to 50 years. Elementary teachers predominated, working in classes with 31-40 students. Voice symptoms and alterations in the perceptual vocal analysis and in the GIRBAS scale were more frequent in GII. In 46 teachers (GI-16; GII-30), videolaryngoscopy exams were abnormal with the vocal nodules being the most frequent lesions. These results indicate that a teacher's voice is compromised, and requires more attention including control of environmental factors and associated diseases, preventive vocal hygiene, periodic laryngeal examinations, and access to adequate specialist treatment.