Laryngeal Activity Research Articles

Intrinsic laryngeal muscle activity in response to autonomic nervous system activation

To determine whether the intrinsic laryngeal muscles exhibit a response to induced autonomic nervous system (ANS) activation, and to characterize responses that may occur. Prospective within-subjects study. A cold pressor (CP) task was used to trigger a whole-body ANS response in eight vocally normal adult females. Surface electromyography of the trapezius muscle and bipolar hook-wire electromyography of intrinsic laryngeal muscles, as well as cardiovascular measures of heart rate (HR) and blood pressure (systolic [SBP] and diastolic [DBP]), were used to characterize participants' response to CP exposure compared to at-rest baseline. Cardiovascular response to the CP task was confirmed for subjects via HR or blood pressure measures. Post hoc Bonferroni analysis confirmed statistically significant increases in HR (P = .027), SBP (P < .001), and DBP (P < .001) during the CP task as compared to baseline. Concurrent increases in muscle activity were generally observed in trapezius, posterior cricoarytenoid, bilateral thyroarytenoid/lateral cricoarytenoid muscle complex, and bilateral cricothyroid muscles for each subject. Three individuals elected to repeat the CP task and displayed the same pattern of laryngeal response as observed in their first exposure. Results for repeated baseline measures obtained after the cessation of the CP task were compared to pre-CP baseline. Overall laryngeal activation remained even after the cardiovascular response was attenuated. Results are consistent with the suggestion that human laryngeal muscles exhibit an elevated level of activation concurrent with ANS activation, and endorse the putative link between laryngeal muscle tension and acute stress. Findings are replicable within a subset of three individuals.

Evidence for swallowing reflexes evoked by acid and mechanical stimulation of the vagal afferent nerves innervating the larynx in anesthetized guinea pigs

PurposeSwallowing protects the lungs from aspiration and is evoked from the upper airways (UA) by activation of pharyngeal afferent nerves. We have tested the hypothesis that laryngeal (LX) afferent nerve activation may also evoke swallowing.MethodsSternohyoid muscle EMGs and UA airflow were used to detect swallows in anesthetized guinea pigs (GPs). Citric acid (CA; 0.01M, 50μL), applied topically to the LX mucosa, and UA pressure distensions, both applied 5× repetitively in 5 min intervals and delivered rostrally via the trachea, were used to evoke swallows.ResultsRepetitive LX CA challenge evoked swallowing (13±5 swallows; n=7). Severing both the recurrent (RLN) and superior (SLN) laryngeal nerves nearly abolished LX CA evoked swallows (0.3±0.3; n=4). Severing just the RLNs also nearly abolished the LX acid‐evoked swallows (1.3±0.9; n=4). By contrast, swallows evoked by 30sec pressure distensions of the UA were not prevented by RLN transection, with all intact (50±5; n=4) and RLN transected (26±3; n=4) GPs swallowing in response to each of 5 distensions. RLN transection did, however, delay the onset of UA distension evoked swallows (4.0±1.3s and 13.6±1.4s in intact and RLN transected GPs; n=4 each). A single, subsequent LX CA challenge evoked swallows in all 4 of these control GPs (4±1) but in none of the GPs with RLNs cut (0±0).ConclusionsLaryngeal vagal afferent nerve activation initiates swallowing.

Effects of IV remifentanil (Remi) on the discharge of canine pontine respiratory group (PRG) neurons in the parabrachial complex (PB)

Mu‐opioids at clinical doses produce bradypnea, which is reversed by microinjection of naloxone into the pontine PB. We studied the effects of the mu‐opioid agonist Remi (IV) on PRG neuron discharge patterns in decerebrate, vagotomized, ventilated, paralyzed dogs. A NeuroNexus 16‐electrode microprobe was used to record from multiple PRG neurons before, during and after IV Remi. Histograms (CTHs) of PRG discharge patterns, triggered from the phrenic neurogram (PNG), were used to quantify Remi effects on ten PRG neuron subtypes. Remi (0.5–0.8 mcg/kg/min) increased TI and TE by 21% and 23% respectively, and decreased peak PNG by 33±3%. PRG neurons (n=197) were located 0.5–2 mm caudal to inferior colliculus, 5–6.5 mm lateral to midline and 2.5–4.5 mm below the dorsal surface. The depression (peak Fn) of all PRG neurons (28±3%; n=197) was similar among 9 of 10 subtypes, but Edec neurons were more depressed (70±6%; n=24; p&lt;0.001). Magnitude of neuronal depression was not related to control Fn, or changes in TI or TE except for Icon neurons and TI (r = −0.72; p&lt;0.001). PRG neurons, except Edec, were less depressed than the peak PNG. Marked depression in PRG Edec neurons may underlie loss of recurrent laryngeal Edec activity. Opioid‐induced depression of PRG subtypes coincident with bradypnea is consistent with reduced excitation to medullary rhythm generation. Supported by VA Merit Review Award: 1 I01 BX000721–01.

Laryngeal involvement in rheumatoid arthritis

AbstractThe prevalence of laryngeal involvement in Rheumatoid Arthritis (RA) ranges from 13 to 75%. The specific RA manifestations include the cricoarytenoid arthritis and the presence of rheumatoid nodules in the vocal folds. ObjectiveThe objective of this study is to evaluate the prevalence of dysphonia and laryngeal alterations on videolaryngoscopy in RA patients and their association with disease activity. MethodThis is a clinical cross-sectional study that evaluated patients with rheumatoid arthritis as to their disease activity score in 28 joints (DAS-28), laryngeal symptoms, application of a Portuguese version of the Voice Handicap Index and videolaryngoscopy findings, comparing them with a control group. ResultsWe evaluated 47 (54%) patients with rheumatoid arthritis and 40 (46%) controls. The prevalence of dysphonia and videolaryngoscopy changes was respectively 12.8% and 72.4% in patients with RA. The mean of DAS-28 was 3.3 ± 1.2; 26 (74.3%) of 35 patients presenting active disease had laryngeal changes (p = 0.713). Posterior laryngitis was the most common diagnosis (44.7%). ConclusionThe prevalence of laryngeal disorders in RA patients was 72.4% and the prevalence of dysphonia was 12.8%. There was no significant relationship between laryngeal disorders and disease activity.

Stereotypic laryngeal and respiratory motor patterns generate different call types in rat ultrasound vocalization.

Rodents produce highly variable ultrasound whistles as communication signals unlike many other mammals, who employ flow-induced vocal fold oscillations to produce sound. The role of larynx muscles in controlling sound features across different call types in ultrasound vocalization (USV) was investigated using laryngeal muscle electromyographic (EMG) activity, subglottal pressure measurements and vocal sound output in awake and spontaneously behaving Sprague-Dawley rats. Results support the hypothesis that glottal shape determines fundamental frequency. EMG activities of thyroarytenoid and cricothyroid muscles were aligned with call duration. EMG intensity increased with fundamental frequency. Phasic activities of both muscles were aligned with fast changing fundamental frequency contours, for example in trills. Activities of the sternothyroid and sternohyoid muscles, two muscles involved in vocal production in other mammals, are not critical for the production of rat USV. To test how stereotypic laryngeal and respiratory activity are across call types and individuals, sets of ten EMG and subglottal pressure parameters were measured in six different call types from six rats. Using discriminant function analysis, on average 80% of parameter sets were correctly assigned to their respective call type. This was significantly higher than the chance level. Since fundamental frequency features of USV are tightly associated with stereotypic activity of intrinsic laryngeal muscles and muscles contributing to build-up of subglottal pressure, USV provide insight into the neurophysiological control of peripheral vocal motor patterns.

Video Laryngostroboscopy

Stroboscopy has improved our understanding of the vocal cord function and has become an important tool in the diagnosis of voice disorders. It has led to changes in diagnosis in approximately 30% of cases when compared to examination with continuous light and mirror. It is important to understand the normal microscopic anatomy of the vocal folds- the plane of movement of the mucosal wave is the superficial layer (Reinke’s space) of lamina propria. Opening and closing of the vocal cords during phonation can be easily seen in mirror examination. The use of high speed motion photography demonstrates additional movements. The equipment required includes stroboscope, camera, recorder, monitor and 90 degree telescope. The following parameters are routinely noted -fundamental frequency, periodicity, amplitude, symmetry, glottic closure, mucosal wave, non vibrating portion, supraglottic activity of larynx. Videostroboscopy helps in differentiating superficial lesions of the epithelium from the deeper lesions involving the muscle. It is useful in diagnosis of early malignancy, vocal nodule, differentiating unilateral paralysis from ankylosis of the cricoarytenoid joint, planning and evaluating phonosurgery. The stroboscopy images can be recorded and stored for future medicolegal purposes in professional voice users and monitoring their treatment. DOI: http://dx.doi.org/10.3329/bjo.v18i2.12010 Bangladesh J Otorhinolaryngol 2012; 18(2): 171-178

FMRI Cerebral Activation during Speech in Laryngectomies

Objective: We focused our attention on the localization of the laryngeal phonatory area in a somatotopic context. This study investigates brain modification consequent to partial or complete removal of the larynx. Methods: From 2009 to 2011 we enrolled 18 patients, divided into 3 groups: 6 healthy volunteers, 6 subtotal laryngectomy patients, and 6 total laryngectomy patients. During fMRI recording, all subjects were trained to carry out 5 motor tasks. Results: Analyzing group 1, we obtained: bilateral activation in prefrontal gyrus and in cerebellar lobule VI during the phonation of the vowel E; activation of the same areas in addition to basal ganglia, cerebellar lobule VI and VIII, insular lobe, 42 Brodmann area and basal gyrus bilaterally, Rolandic operculum, and the supplementary motor area intonating vowel E. Glottal adduction during forced expiration and phonatory task activated the same areas. Phonatory tasks determined the same activation in all groups, with an extension of these areas proportional to surgical damage. In lip and tongue tasks we observed the same results in all groups. Conclusion: This study permitted the mapping of the human motor cortical areas that control intrinsic laryngeal muscles, differentiating them from those referable to the articulatory process. Studying subtotal and total laryngectomies, we identified an expansion of the laryngeal area activation, proportional to the degree of the laryngeal injury. We observed the functional recovery of brain regions considered evolutionarily ancient that are normally virtually quiescent.

Acoustic Effects of Asymmetric Laryngeal Activation

Objective: Symmetric activation of laryngeal intrinsic musculature is considered essential for optimal voice production. However, phonatory consequences of asymmetric laryngeal activation are poorly understood. The objective of this study was to investigate the phonatory characteristics of an asymmetrically activated larynx. Methods: Bilateral recurrent laryngeal nerves (RLNs) were stimulated in a graded fashion (from threshold to maximal activation) in a canine phonation model. 121 combinations of left-right RLN activation states (spanning symmetric and asymmetric activation states) were analyzed for phonatory instabilities (number of bifurcations) in the 1.5s acoustic signal after neuromuscular activation. Results: Asymmetric laryngeal activation produced frequent phonatory instabilities. Highest levels of instabilities were seen during phonation at extreme asymmetric conditions and asymmetries during near-maximum RLN stimulation. Linear regression models demonstrated significant association ( P &lt; .01) between percent of RLN stimulation and acoustic/aerodynamic measures. Phonation onset time (ms) (Left RLN: Coef = 1.44, CI = 1.01-1.86; Right RLN: Coef = 2.71, CI = 2.29-3.13) and subglottic pressure (kPa) (Left RLN: Coef = 0.01, CI = 0.011-0.014; Right RLN: Coef = 0.01, CI = 0.009-0.013) increased with increasing RLN stimulation. Subglottic airflow (l/min) (Left RLN: Coef = −0.29, CI = −0.36-0.20; Right RLN: Coef = −0.29, CI = −0.37-0.21) and fundamental frequency (Hz) (Left RLN: Coef = −0.59, CI = −0.76-0.42; Right RLN: Coef = −0.24, CI = −0.41-0.07) decreased with increasing RLN stimulation. Conclusion: Higher levels of asymmetric laryngeal activation are associated with increasing phonatory instabilities. These results can be applied to further characterize asymmetric laryngeal states that lead to vocal irregulaties.

Recurrent laryngeal nerve activity exhibits a 5-HT-mediated long-term facilitation and enhanced response to hypoxia following acute intermittent hypoxia in rat

A progressive and sustained increase in inspiratory-related motor output ("long-term facilitation") and an augmented ventilatory response to hypoxia occur following acute intermittent hypoxia (AIH). To date, acute plasticity in respiratory motor outputs active in the postinspiratory and expiratory phases has not been studied. The recurrent laryngeal nerve (RLN) innervates laryngeal abductor muscles that widen the glottic aperture during inspiration. Other efferent fibers in the RLN innervate adductor muscles that partially narrow the glottic aperture during postinspiration. The aim of this study was to investigate whether or not AIH elicits a serotonin-mediated long-term facilitation of laryngeal abductor muscles, and if recruitment of adductor muscle activity occurs following AIH. Urethane anesthetized, paralyzed, unilaterally vagotomized, and artificially ventilated adult male Sprague-Dawley rats were subjected to 10 exposures of hypoxia (10% O(2) in N(2), 45 s, separated by 5 min, n = 7). At 60 min post-AIH, phrenic nerve activity and inspiratory RLN activity were elevated (39 ± 11 and 23 ± 6% above baseline, respectively). These responses were abolished by pretreatment with the serotonin-receptor antagonist, methysergide (n = 4). No increase occurred in time control animals (n = 7). Animals that did not exhibit postinspiratory RLN activity at baseline did not show recruitment of this activity post-AIH (n = 6). A repeat hypoxia 60 min after AIH produced a significantly greater peak response in both phrenic and RLN activity, accompanied by a prolonged recovery time that was also prevented by pretreatment with methysergide. We conclude that AIH induces neural plasticity in laryngeal motoneurons, via serotonin-mediated mechanisms similar to that observed in phrenic motoneurons: the so-called "Q-pathway". We also provide evidence that the augmented responsiveness to repeat hypoxia following AIH also involves a serotonergic mechanism.

The role of botulinum toxin in the management of airway compromise due to bilateral vocal fold paralysis

The management of a patient with bilateral vocal fold motion impairment (BVFMI) can be challenging for the otolaryngologist. The treatment traditionally involves tracheotomy, which can be very distressful for some patients. Alternatively, there are endoscopic procedures, which irreversibly sacrifice voice in order to improve airway. The optimal treatment of BVFMI still eludes us. The purpose of this review is to highlight an alternate management strategy for bilateral vocal fold paralysis using botulinum toxin (BTX). This procedure is predicated on the premise that vocal fold immobility is related to synkinetic reinnervation of the vocal fold. Eliminating any thyroarytenoid/lateral cricoarytenoid (LCA) activity during respiratory gestures should allow greater unopposed posterior cricoarytenoid abduction. There have been several case reports and series, the largest of which involved 11 patients, describing the successful use of BTX for this application. The best candidates for this adductor chemical denervation are those patients who have undergone trauma to the recurrent laryngeal nerve without evidence of cricoarytenoid joint fixation. Patients should have evidence of voluntary thyroarytenoid/LCA laryngeal electromyography activity, though true synkinesis cannot always be reliably identified. The procedure can be another management option for patients with BVFMI.

Korean perception of the Japanese voiceless alveolar fricative /s/

Korean voiceless obstruents exhibit a relatively unique phonemic contrast based on laryngeal activity, a three-way tense, lax, and aspirated contrast for stops and affricates and a two-way tense and lax contrast for the alveolar fricative /s/. The relative primacy of various cues to the distinction, particularly for the affricate and fricative contrasts, remains controversial. Patterns in the adaptation of English loanwords have been used to infer the phonological basis for the mapping of English /s/ to Korean, however perception studies have shown that loanword adaptations do not fully account for the synchronic phonological mapping from English loans by Korean native speakers (Schmidt 1996). Mapping from Japanese /s/ to Korean has been much less studied, but according to a loanword study by Ito et al. (2006), Japanese /s/ in word-initial and medial position is consistently mapped to Korean lax /s/, and geminate /s/ is consistently mapped to Korean tense /s*/. However, there appears to have been no comparable perception study to show synchronic mapping by Korean native speakers. The current study undertakes a preliminary evaluation of perceptual mapping of Japanese /s/ to Korean and finds that though the word initial Japanese /s/ conforms to loan-word predictions, word-medial /s/ does not.

Functional MRI assessment of orofacial articulators: neural correlates of lip, jaw, larynx, and tongue movements.

Compared with complex coordinated orofacial actions, few neuroimaging studies have attempted to determine the shared and distinct neural substrates of supralaryngeal and laryngeal articulatory movements when performed independently. To determine cortical and subcortical regions associated with supralaryngeal motor control, participants produced lip, tongue and jaw movements while undergoing functional magnetic resonance imaging (fMRI). For laryngeal motor activity, participants produced the steady-state/i/vowel. A sparse temporal sampling acquisition method was used to minimize movement-related artifacts. Three main findings were observed. First, the four tasks activated a set of largely overlapping, common brain areas: the sensorimotor and premotor cortices, the right inferior frontal gyrus, the supplementary motor area, the left parietal operculum and the adjacent inferior parietal lobule, the basal ganglia and the cerebellum. Second, differences between tasks were restricted to the bilateral auditory cortices and to the left ventrolateral sensorimotor cortex, with greater signal intensity for vowel vocalization. Finally, a dorso-ventral somatotopic organization of lip, jaw, vocalic/laryngeal, and tongue movements was observed within the primary motor and somatosensory cortices using individual region-of-interest (ROI) analyses. These results provide evidence for a core neural network involved in laryngeal and supralaryngeal motor control and further refine the sensorimotor somatotopic organization of orofacial articulators.

Co-Transplantation of Olfactory Ensheathing Cells from Mucosa and Bulb Origin Enhances Functional Recovery after Peripheral Nerve Lesion

Olfactory ensheathing cells (OECs) represent an interesting candidate for cell therapy and could be obtained from olfactory mucosa (OM-OECs) or olfactory bulbs (OB-OECs). Recent reports suggest that, depending on their origin, OECs display different functional properties. We show here the complementary and additive effects of co-transplanting OM-OECs and OB-OECs after lesion of a peripheral nerve. For this, a selective motor denervation of the laryngeal muscles was performed by a section/anastomosis of the recurrent laryngeal nerve (RLN). Two months after surgery, recovery of the laryngeal movements and synkinesis phenonema were analyzed by videolaryngoscopy. To complete these assessments, measure of latency and potential duration were determined by electrophysiological recordings and myelinated nerve fiber profiles were defined based on toluidine blue staining. To explain some of the mechanisms involved, tracking of GFP positive OECs was performed. It appears that transplantation of OM-OECs or OB-OECs displayed opposite abilities to improve functional recovery. Indeed, OM-OECs increased recuperation of laryngeal muscles activities without appropriate functional recovery. In contrast, OB-OECs induced some functional recovery by enhancing axonal regrowth. Importantly, co-transplantation of OM-OECs and OB-OECs supported a major functional recovery, with reduction of synkinesis phenomena. This study is the first which clearly demonstrates the complementary and additive properties of OECs obtained from olfactory mucosa and olfactory bulb to improve functional recovery after transplantation in a nerve lesion model.

Spasmodic Dysphonia Translocated via Reinnervated Ansa Cervicalis

Objective: Illustrate the first reported case of recurrent adductor spasmodic dysphonia (ADSD) after bilateral selective laryngeal adductor denervation-reinnervation (SLAD-R) surgery presenting with dystonia of the strap muscles and adductors of the larynx. Method: A 40-year-old man presented with ADSD. The patient underwent a bilateral SLAD-R surgery 10 years ago after botulinum toxin failure. The laryngeal dystonia was quiescent until 2 years ago when the patient noted worsening tension in his voice temporally associated with muscle spasm of his anterior neck. Results: The patient elected to undergo re-exploration of his neck with lysis of his ansa cervicalis reinnervation. The operation revealed bilaterally intact neurorrhaphies between the superior root of the ansa cervicalis and the distal recurrent laryngeal nerves. Electrical stimulation of the superior roots of the ansa cervicalis produced laryngeal adductor activity as evidenced by an electromyography nerve monitor and by palpation of the arytenoids cartilage. The neurorrhaphies were sectioned and postoperatively the patient’s dystonias immediately resolved. Conclusion: We present a case of demonstrated functional activity of nerves used for reinnervation in SLAD-R surgery for spasmodic dysphonia. Unfortunately in this case, the disease recurred through aberrant activity mediated via the translocated ansa cervicalis nerves.

Microinjection of kynurenic acid (KA) into the medial reticular formation elicits dysphagic swallow motor patterns in the anesthetized cat

Kynurenic acid (KA), an endogenous compound with activities at multiple neurotransmitter receptors, is found in higher concentrations in the central nervous system of patients with Alzheimer's and Parkinson's disease. A leading cause of death in these disorders is aspiration pneumonia, caused by dysphagia and dystussia. The medial reticular formation (MRF) caudal to obex is important for cough coordination. We speculate this region is also important for swallow. Electromyograms (EMG) of geniohyoid (GH), thyroarytenoid (ThAr), upper esophageal sphincter (UES), and thyrohyoid (TH) were recorded in anesthetized cats. Swallowing was elicited by injection of water into the pharynx. KA (50nL; 50mM) was microinjected bilaterally at 4 locations within the MRF. There was significant suppression of EMG magnitudes for TH, ThAr, and GH during swallow 20 min after microinjections. At 2 hours post-injections, EMG magnitudes began returning to control values. However, disruption of temporal coordination of the EMGs persisted. Complete resolution of the suppressive effect and temporal discoordination during swallow was observed at 4 hours. We conclude that neurons within the MRF are important for control of laryngeal and pharyngeal motoneuron activity during swallow. These results support the hypothesis that the swallow control network includes MRF neurons caudal to obex. Supported by NIH HL 89104; HL 103415.

High-speed image analysis reveals chaotic vibratory behaviors of pathological vocal folds

Laryngeal pathology is usually associated with irregular dynamics of laryngeal activity. High-speed imaging facilitates direct observation and measurement of vocal fold vibrations. However, chaotic dynamic characteristics of aperiodic high-speed image data have not yet been investigated in previous studies. In this paper, we will apply nonlinear dynamic analysis and traditional perturbation methods to quantify high-speed image data from normal subjects and patients with various laryngeal pathologies including vocal fold nodules, polyps, bleeding, and polypoid degeneration. The results reveal the low-dimensional dynamic characteristics of human glottal area data. In comparison to periodic glottal area series from a normal subject, aperiodic glottal area series from pathological subjects show complex reconstructed phase space, fractal dimension, and positive Lyapunov exponents. The estimated positive Lyapunov exponents provide the direct evidence of chaos in pathological human vocal folds from high-speed digital imaging. Furthermore, significant differences between the normal and pathological groups are investigated for nonlinear dynamic and perturbation analyses. Jitter in the pathological group is significantly higher than in the normal group, but shimmer does not show such a difference. This finding suggests that the traditional perturbation analysis should be cautiously applied to high speed image signals. However, the correlation dimension and the maximal Lyapunov exponent reveal a statistically significant difference between normal and pathological groups. Nonlinear dynamic analysis is capable of quantitatively describing the aperiodic vocal fold vibrations and may be helpful for understanding disordered behaviors in pathological laryngeal systems.

Theoretical Modeling and Experimental High-Speed Imaging of Elongated Vocal Folds

In this paper, the role of vocal fold elongation in governing glottal movement dynamics was theoretically and experimentally investigated. A theoretical model was first proposed to incorporate vocal fold elongation into the two-mass model. This model predicted the direct and nondirect components of the glottal time series as a function of vocal fold elongation. Furthermore, high-speed digital imaging was applied in excised larynx experiments to visualize vocal fold vibrations with variable vocal fold elongation from -10% to 50% and subglottal pressures of 18- and 24-cm H(2)O. Comparison between theoretical model simulations and experimental observations showed good agreement. A relative maximum was seen in the nondirect component of glottal area, suggesting that an optimal elongation could maximize the vocal fold vibratory power. However, sufficiently large vocal fold elongations caused the nondirect component to approach zero and the direct component to approach a constant. These results showed that vocal fold elongation plays an important role in governing the dynamics of glottal area movement and validated the applicability of the proposed theoretical model and high-speed imaging to investigate laryngeal activity.

Arytenoid Abduction: Indications and Limitations

Objectives I report further experience with arytenoid abduction (AAb), a procedure that enlarges the glottis by external rotation of the arytenoid cartilage and thus moves the vocal process laterally and rostrally, but does not preclude adduction for phonation. Therefore, AAb has the potential to preserve voice in patients with bilateral abductor laryngeal paralysis. Methods I performed a retrospective review of AAb in 11 patients with bilateral laryngeal paralysis and 3 patients with other neurologic causes of glottal airway compromise, ie, adductor breathing dystonia, frequent laryngospasm, and progressive laryngeal breathing dysfunction. Results Seven of the 11 patients with bilateral paralysis had dramatic airway improvement. One patient required a tracheotomy after AAb, and 3 patients with an existing tracheotomy could not be decannulated. Arytenoid abduction relieved airway obstruction in the patient with recurrent laryngospasm and in the child with progressive laryngeal breathing dysfunction, but the patient with adductor breathing dystonia has persistent stridor. The factors associated with a poor airway outcome included prolonged tracheotomy, electromyographic evidence of inspiratory activity of adductor muscles, chronic obstructive pulmonary disease, sleep apnea, and prior cordotomy or arytenoidectomy. Conclusions Arytenoid abduction is most effective in patients with bilateral laryngeal paralysis of less than 1 year's duration who do not have unfavorable laryngeal adductor activity.

Entrenamiento del vibrato en cantantes

TEMA: El vibrato de la voz es uno de los rasgos acústicos, técnicos y estilísticos más importantes en la caracterización de la cualidad de la voz en cantantes clásicos. Técnicamente, vibrato es una pulsación del tono, usualmente acompañada con pulsaciones sincrónicas de intensidad y timbre. El vibrato puede ser descrito acústicamente por el rate, extent y periodicidad de las modulaciones en frecuencia y modulaciones de la amplitud de la voz. El objetivo del presente artículo es mostrar y explicar un nuevo procedimiento para entrenar y corregir vibrato en cantantes. PROCEDIMIENTOS: Estudiante de canto lirico de 25 años, sexo masculino con clasificación vocal de barítono lirico, voz normal desde el punto de vista perceptual. La corrección del vibrato se realiza por medio del método "Entrenamiento rítmico del vibrato". Se produce la subdivisión rítmica de un pulso durante la emisión de una vocal con un "tempo" o velocidad constante. Posteriormente se varía la velocidad del pulso, las vocales y la melodía del ejercicio. Los parámetros acústicos del vibrato son evaluados objetivamente antes y después del entrenamiento. RESULTADOS: el paciente logró producir un vibrato con rate, extent y regularidad dentro de rangos normales. Esto se realizó de forma consciente y dirigida, utilizando actividad laríngea y abdominal en forma conjunta. La naturalidad del vibrato continuó mejorando después de finalizado el entrenamiento. CONCLUSIONES: es posible el entrenamiento y/o corrección del vibrato en forma dirigida a través de ejercicios específicos destinados a ese objetivo. El apoyo visual cumple un rol importante en los resultados obtenidos.

Graded activation of the intrinsic laryngeal muscles for vocal fold posturing.

Previous investigations using in vivo models to study the role of intrinsic laryngeal muscles in phonation have used neuromuscular stimulation to study voice parameters. However, these studies used coarse stimulation techniques using limited levels of neuromuscular stimulation. In the current investigation, a technique for fine control of laryngeal posturing was developed using graded stimulation of the laryngeal nerves. Vocal fold strain history to graded stimulation and a methodology for establishing symmetric laryngeal activation is presented. This methodology has immediate applications for the study of laryngeal paralysis and paresis, as well as general questions of neuromuscular control of the larynx.