Extrinsic Laryngeal Muscles Research Articles

Síndrome de tensão musculoesquelética, musculatura laríngea extrínseca e postura corporal: considerações teóricas

O tema deste estudo é a Síndrome de tensão musculoesquelética, musculatura laríngea extrínseca e postura corporal. Tem como objetivo descrever, a partir de revisão de literatura,as características da musculatura extrínseca da laringe; postura corporal; Síndrome de tensão musculoesquelética e suas implicações vocais; avaliação e tratamento fisioterapêutico e fonoaudiológico. Foi realizado levantamento bibliográfico dos últimos 13 anos em que foram incluídos artigos cujo objetivo e/ou corpo do texto estivessem em consonância com os objetivos do estudo. A pesquisa foi realizada nos bancos de dados das bases Literatura Latino-Americana e do Caribe em Ciências da Saúde, Biblioteca Regional de Medicina, PublicMedline, Medical Literature Analysis and Retrieval System on Line, Scientific Electronic Library Online e Google Schoolar. Estabeleceram-se relações importantes do âmbito fisioterapêutico e fonoaudiológico, dentre as quais se destacam as relações musculares, posturais e funcionais na sinergia do aparato vocal. Na fisioterapia para redução da tensão muscular, a literatura aponta uso de eletroterapia transcutânea, laser de baixa intensidade, laser acupuntura, crioterapia, bem como terapia manual com tração, massagens, manipulações e mobilizações cervicais, associadas ou não a exercícios, alongamentos, relaxamento isométrico, mobilização assistida dos tecidos moles, exercícios terapêuticos visando à correção e equilíbrio muscular, reeducação respiratória diafragmática e terapia com flexão craniocervical. Na fonoaudiologia, foram encontrados apenas estudos com a manipulação digital da laringe e exercícios de trato vocal semiocluído.

Electrical Activity of Extrinsic Laryngeal Muscles in Subjects With and Without Dysphonia

To compare dysphonic individuals to nondysphonic with regards to electrical activity of extrinsic laryngeal muscles related to perceptual and acoustic vocal parameters. Dysphonic individuals have higher electrical activity in the supra and infrahyoid muscles than those nondysphonic. Prospective, cross-sectional, case series study. Forty-one subjects, divided into two groups according to the presence of dysphonia, underwent evaluation of surface electromyography, auditory-perceptual, and acoustic evaluations of voice during the vocal rest and sustained emissions of the vowel /ε/ and count of 20 to 30 at usual and strong intensities. The dysphonic group differed significantly from the nondysphonic by (1) lower electrical activity normalized by the maximum sustained voluntary activity evaluated in all tasks of phonation in the suprahyoid group; (2) lower recruitment of electrical activity in emissions of strong intensity compared with those of usual intensity in the suprahyoid muscles to emit the vowel /ε/ (13.66 ± 5.17 in dysphonic group and 35.20 ± 7.60 in the nondysphonic group, P = 0.029) and in the infrahyoid muscles in the count of 20 to 30 (14.90 ± 4.69 vs. 42.01 ± 6.15; P < 0.001) and to emit the vowel /ε/ (11.47 ± 6.52 vs. 22.66 ± 9.05, P < 0.001); (3) lower vocal intensity to produce the vowel /ε/ in usual and strong intensities and count in strong intensity. The electrical activities of the maximum sustained voluntary activity were reduced with increasing degree of dysphonia. There was lower electrical activity of the extrinsic laryngeal muscles in dysphonic individuals compared with nondysphonic, and related to the degree of dysphonia.

Somatotopy of the extrinsic laryngeal muscles in the human sensorimotor cortex

The larynx is the major organ of vocalization. The intrinsic laryngeal muscles modify the internal shape of the larynx while the extrinsic laryngeal muscles move the entire larynx vertically in the airway. Previous neuroimaging research has established the somatotopic location of the intrinsic musculature of the larynx in the human motor cortex and showed it to be in an evolutionarily novel location compared to the homologous region in monkey cortex. In the current study, we attempted for the first time to determine the somatotopic localization of the extrinsic laryngeal musculature in humans. In a functional magnetic resonance imaging experiment, we had participants voluntarily move their larynx upward and/or downward in the airway in the absence of vocalization to engage the extrinsic laryngeal muscles or vocalize in the absence of vertical laryngeal movement to engage the intrinsic laryngeal muscles. Vertical movement of the larynx activated ventral pericentral sensorimotor cortex extending dorsally to overlap with the representation of the intrinsic laryngeal muscles. This pattern is a reversal from the somatotopy of the monkey, where the extrinsic laryngeal muscles are represented dorsally to the intrinsic laryngeal muscles.

Clinical analysis of 109 cases of recurrent papillary thyroid carcinoma

Objective: To explore the factors related to recurrence of PTC (papillary thyroid carcinoma) and the sites of recurrence, in order to seek for the proper treatment of these cases. Methods: The clinical and follow-up data of 109 cases of recurrent PTC in Tianjin Medical University Cancer Hospital from January 2008 to January 2012 were analyzed retrospec­tively, and 350 cases of PTC without recurrence in the same period were also collected as the controls. The univariate and multivariate analyses were performed to find out the recurrence-related factors. Results: The univariate analysis revealed that initial operative approach, TNM stage and pathological subtype were associated with recurrence (P 0.05). Multivariate analysis indicated that initial operative approach and pathological subtype were the dependent factors for recurrence (P < 0.05). Of 109 cases, 20 (18.3%) were confirmed as residual carcinoma by pathology. The involved sites of recurrence included regions of lymph nodes (34 in group Ⅱ, 54 in group Ⅲ, 58 in group Ⅳ, 12 in group Ⅴ, 68 in group Ⅵ), soft tissues (5 in group Ⅱ, 6 in group Ⅲ, 9 in group Ⅳ, 0 in group Ⅴ, 8 in group Ⅵ), muscles (2 in anterior cervical muscle, 1 in extrinsic laryngeal muscle, and 0 in sternocleidomastoid), parathyroid (n = 1), laryngeal recurrent nerve (n = 3), esophagus (n = 1) and trachea (n = 2). Five cases developed pulmonary metastasis, and 1 case developed liver and bone metastases. Conclusion: For the PTC patients who have the possibility of recurrence, the reinforced postoperative follow-up should be required. Furthermore, regular reexamination is also needed for possible recurrent regions. Once the recurrence occurres, active and standardized therapy is suggested for PTC. DOI:10.3781/j.issn.1000-7431.2013.08.012

Laryngeal Aerodynamics in Children with Hearing Impairment versus Age and Height Matched Normal Hearing Peers

Lack of proper auditory feedback in hearing-impaired subjects results in functional voice disorder. It is directly related to discoordination of intrinsic and extrinsic laryngeal muscles and disturbed contraction and relaxation of antagonistic muscles. A total of twenty children in the age range of 5–10 years were considered for the study. They were divided into two groups: normal hearing children and hearing aid user children. Results showed a significant difference in the vital capacity, maximum sustained phonation, and fast adduction abduction rate having equal variance for normal and hearing aid user children, respectively, but no significant difference was found in the peak flow value with being statistically significant. A reduced vital capacity in hearing aid user children suggests a limited use of the lung volume for speech production. It may be inferred from the study that the hearing aid user children have poor vocal proficiency which is reflected in their voice. The use of voicing component in hearing impaired subjects is seen due to improper auditory feedback. It was found that there was a significant difference in the vital capacity, maximum sustained phonation (MSP), and fast adduction abduction rate and no significant difference in the peak flow.

Use of surface electromyography in phonation studies: an integrative review.

SummaryIntroduction: Surface electromyography has been used to assess the extrinsic laryngeal muscles during chewing and swallowing, but there have been few studies assessing these muscles during phonation. Objective: To investigate the current state of knowledge regarding the use of surface electromyography for evaluation of the electrical activity of the extrinsic muscles of the larynx during phonation by means of an integrative review. Method: We searched for articles and other papers in the PubMed, Medline/Bireme, and Scielo databases that were published between 1980 and 2012, by using the following descriptors: surface electromyography and voice, surface electromyography and phonation, and surface electromyography and dysphonia. The articles were selectedon the basis ofinclusion and exclusion criteria. Data Synthesis: This was carried out with a cross critical matrix. We selected 27 papers,i.e., 24 articles and 3 theses. The studies differed methodologically with regards to sample size and investigation techniques, making it difficult to compare them, but showed differences in electrical activity between the studied groups (dysphonicsubjects, non-dysphonicsubjects, singers, and others). Conclusion: Electromyography has clinical applicability when technical precautions with respect to application and analysis are obeyed. However, it is necessary to adopt a universal system of assessment tasks and related measurement techniques to allow comparisons between studies.

Understanding the Mechanics of Laryngospasm Is Crucial for Proper Treatment

To the Editor: In their case scenario, “Perianesthetic management of laryngospasm in children,” Orlianguet et al. 1presented a 10-month-old boy who developed an inspiratory stridor after sevoflurane induction, which was initially managed by a jaw thrust and positive pressure ventilation. When the stridor recurred, manual ventilation became difficult with increased resistance to insufflation. Despite a jaw thrust, positive pressure ventilation with FIO2= 1, and propofol, the obstruction was not relieved and severe hypoxemia (oxygen saturation measured by pulse oximetry, or SpO2, = 52%) ensued, requiring the administration of succinylcholine and tracheal intubation.A basic understanding of the mechanics of laryngospasm is crucial for proper treatment.2In his classic article, Fink described three types of laryngospasm: expiratory stridor, inspiratory stridor, and ball-valve obstruction.3The stridors are controlled by the intrinsic laryngeal muscles, whereas the ball-valve closure is controlled by both the intrinsic and extrinsic laryngeal muscles. The expiratory stridor occurs as a result of active adduction of the vocal cords. The inspiratory stridor is produced passively as a result of the loss of tone of the abductor muscles. Because the velocity is greater where the passage is most narrow, airway pressure at the subglottic area becomes less than atmospheric during inspiratory efforts, and the passage of gases through the glottis generates a force that approximates the vocal cords together resulting in inspiratory stridor. Positive airway pressure can stent the airway and correct both expiratory and inspiratory stridors.3In ball-valve obstruction, laryngeal closure occurs at three levels: the true vocal cords, the false cords, and the redundant supraglottic tissue.3,4The approximation of the vocal cords (and false cords) is swiftly followed by contraction of the extrinsic laryngeal muscles, shortening of the thyrohyoid distance resulting in complete closure, and cessation of airflow.3,4In this situation, applying positive pressure can worsen the obstruction,3as evidenced in the current case. By distending both pyriform fossae, the aryepiglottic folds are pressed more firmly against each other, which reinforces the closure.3In contrast, the jaw thrust (also referred to as maximum mandibular advancement)5can be effective in correcting ball-valve closure. The forward mandibular movement is transmitted through the geniohyoid muscles to the hyoid bone and the hyoepiglottic ligament. Consequently, the epiglottis and the redundant supraglottic tissue are pulled away from the false cords, and the laryngeal passage is reopened.3However, it is frequently necessary, as in the case presented by Orlianguet et al. , to administer succinylcholine to relieve this type of severe obstruction.It is interesting that the expiratory stridor, which was common in the days of ether anesthesia and was regarded as “a vocal protest by the patient against inadequate anesthesia,” has virtually disappeared in modern anesthesia practice. In our recent quality-improvement study of laryngospasm, expiratory stridor did not occur in any patient. This is probably related to the use of sevoflurane yielding faster induction because of its low blood/gas partition coefficient.We propose a simple algorithm (fig. 1) for the management of laryngospasm, which can be easily remembered and utilized by clinicians. Based on the mechanics of laryngospasm, this algorithm addresses both inspiratory stridor and ball-valve obstruction, but ignores the expiratory stridor because it is no longer observed in modern anesthesia practice. Positive pressure, which is effective in the management of inspiratory stridor, is avoided in ball-valve obstruction because it can worsen the obstruction. If a jaw thrust fails to correct ball-valve obstruction, succinylcholine is administered, followed by positive pressure ventilation and tracheal intubation.

Anatomical Study of the LarynxIn Indigenous Male Turkey (Meleagris gallopava)

The study aim to explain the anatomical description of the larynx in the indigenous male turkey (Meleagris gallopava). For making use as a basic information in the study of the respiratory physiology, histopathology, the respiratory diseases diagnosis, and surgery and anesthesia of turkey. Five healthy birds (first year of age and weighing (4715 ± 43.3 gm)) employed in this study. After well bleeding, the larynx detected, and then the shape, position, dimensions of each specimen and its components were recorded. The larynx appeared as a heart-shaped mound in the caudal part of the oropharyngeal cavity. It consisted of a single hyaline cricoid cartilage which consisted of body and left and right wings, double hyaline arytenoid cartilages which consisting of body and rostral and caudal processes, and single hyaline procricoid cartilage which consisted of body dorsally and tail ventrally. Also there were superficial and deep intrinsic and rostral, caudolateral, and caudomedial extrinsic laryngeal skeletal muscles.

Cytochrome c Oxidase Deficiency in Human Posterior Cricoarytenoid Muscle

Mitochondrial alterations occur in skeletal muscle fibers throughout the normal aging process, resulting from increased accumulation of reactive oxide species (ROS). These result in respiratory chain abnormalities, which decrease the oxidative capacity of muscle fibers, leading to decreased contractile force, sarcopenia, or fiber necrosis. Intrinsic laryngeal muscles are a cranial muscle group that possesses some distinctive genotypic, phenotypic, and physiologic properties. Their susceptibility to mitochondrial alterations resulting from biological processes that increase levels of oxidative stress may be one of these distinctive characteristics. The incidence of cytochrome c oxidase (COX) deficiency (COX(-)) was determined in human posterior cricoarytenoid (PCA) muscle when compared with the human thyrohyoid (TH) muscle, an extrinsic laryngeal muscle that served as "control" muscle. Ten PCA and 10 TH muscles were harvested postlaryngectomy from 10 subjects ranging in age from 55 to 86 years. Differences in COX(-) were compared within and between muscle types using tissue section staining and standard morphometric analysis. COX(-) fibers were identified in both the PCA and TH muscles. The PCA muscle had 10 times as may affected fibers as the TH muscle, with significant differences in COX(-) found between muscle type and fiber type (P=0.003). Almost all of this effect was the result of elevated levels of COX(-) in type I fibers from the PCA muscle (P=0.002) that showed a strong positive correlation with increased age. These results suggest that increased mitochondrial alterations may occur in the PCA muscle during normal aging.

Embryonic origins of avian and mammalian laryngeal musculoskeletal structures

The larynx forms at the boundary of neural crest‐ and mesoderm‐derived tissues, but the interface site in relation to laryngeal cartilages is uncertain. Our research identifies crest and mesoderm contributions to laryngeal cartilages and muscles in the chick, which has only cricoid and arytenoid cartilages, and in mice with thyroid and epiglottal elements. This was done using quail‐chick transplants and LacZ‐retroviral labeling; for mice labeling of crest‐derived tissues used the Wnt1‐cre/R26R reporter. Chick laryngeal cartilages are derived from lateral mesoderm beside the first somite; intrinsic muscles are from this somite. Mouse epiglottis and thyroid cartilages derive from crest cells; arytenoids do not. The cricoid is mesodermal, but a few crest‐derived chondrocytes may be present in its dorsal plate. Fetal thyroid and cricoid cartilages transiently fuse, and secondarily form a joint whose location does not precisely correspond to the original crest:mesoderm interface. Additional crest labeling is present in the perichondrium at sites of cranially‐oriented extrinsic laryngeal muscle attachment. Crest‐derived Schwann cells and ganglia were widely dispersed beneath the laryngeal mucosa. These studies show that neural crest contributes to the larynx only in those cartilages that are located rostrally and are unique to mammals. Supported by NIH grants EY015917 to DMN and DK081634‐01 MLE.

Projections of the ventrolateral pontine vocalization area in the squirrel monkey

In four squirrel monkeys (Saimiri sciureus), the tracer biotin dextranamine (BDA) was injected into the ventrolateral pons at a site at which injection of the glutamate antagonist kynurenic acid blocked vocalization electrically elicited from the periaqueductal gray (PAG). Anterograde projections could be traced into all cranial motor and sensory nuclei involved in phonation, that is, the nucleus ambiguus, facial, hypoglossal and trigeminal motor nuclei, the motorneuron column in the ventral gray substance innervating the extrinsic laryngeal muscles, the nucleus retroambiguus, solitary tract and spinal trigeminal nuclei. Projections were also found into a number of auditory nuclei, namely the nucleus cochlearis-complex, superior olive, ventral and dorsal nuclei of the lateral lemniscus and inferior colliculus. Furthermore, there were projections into the reticular formation of the lateral and dorsocaudal medulla and lateral pons, into nucleus gracilis, inferior and medial vestibular nuclei, lateral reticular nucleus, ventral raphe, pontine gray, superior colliculus, PAG and mediodorsal thalamic nucleus. Injection of the tracer wheat germ agglutinin-conjugated horseradish peroxidase into the ventrolateral pontine vocalization-blocking area in one animal yielded retrograde labeling throughout the PAG. Injection of BDA into a vocalization-eliciting site of the PAG in another animal yielded projections into the ventrolateral pontine vocalization-blocking area. It is concluded that the ventral paralemniscal area in the ventrolateral pons represents a relay station of the descending periaqueductal vocalization-controlling pathway.

Remapping Auditory-Motor Representations in Voice Production

Evidence regarding visually guided limb movements suggests that the motor system learns and maintains neural maps between motor commands and sensory feedback. Such systems are hypothesized to be used in a feed-forward control strategy that permits precision and stability without the delays of direct feedback control. Human vocalizations involve precise control over vocal and respiratory muscles. However, little is known about the sensorimotor representations underlying speech production. Here, we manipulated the heard fundamental frequency of the voice during speech to demonstrate learning of auditory-motor maps. Mandarin speakers repeatedly produced words with specific pitch patterns (tone categories). On each successive utterance, the frequency of their auditory feedback was increased by 1/100 of a semitone until they heard their feedback one full semitone above their true pitch. Subjects automatically compensated for these changes by lowering their vocal pitch. When feedback was unexpectedly returned to normal, speakers significantly increased the pitch of their productions beyond their initial baseline frequency. This adaptation was found to generalize to the production of another tone category. However, results indicate that a more robust adaptation was produced for the tone that was spoken during feedback alteration. The immediate aftereffects suggest a global remapping of the auditory-motor relationship after an extremely brief training period. However, this learning does not represent a complete transformation of the mapping; rather, it is in part target dependent.

Functional dysphonia.

Functional dysphonia-a voice disturbance in the absence of structural or neurologic laryngeal pathology-is an enigmatic and controversial voice disorder that is frequently encountered in multidisciplinary voice clinics. Poorly regulated activity of the intrinsic and extrinsic laryngeal muscles is cited as the proximal cause of functional dysphonia, but the origin of this dyregulated laryngeal muscle activity has not been fully elucidated. Several causes have been cited as contributing to this imbalanced muscle tension; however, recent research evidence points to specific personality traits as important contributors to its development and maintenance. Voice therapy by an experienced speech-language pathologist remains an effective short-term treatment for functional dysphonia in the majority of cases, but less is known regarding the long-term fate of such intervention. Further research is needed to better understand the pathogenesis of functional dysphonia, and factors contributing to its successful management.

Synchrony of laryngeal muscle activity in persons with vocal tremor.

To determine if the tremor activity in laryngeal muscles is synchronous, which would indicate a single central source of tremor. Six persons with vocal tremor participated in this study. Laryngeal muscle activity was recorded from 2 intrinsic and 2 extrinsic laryngeal muscles during production of a sustained \i\ sound. Correlations were computed between electromyographic activity in pairs of laryngeal muscles to measure the degree to which electromyographic activity in one muscle was synchronous with electromyographic activity in another laryngeal muscle. In addition, correlations were computed between each of the 4 laryngeal muscles and the voice signal to determine which muscle had activity that was most highly related to amplitude modulations in the voice. Multiple samples from each subject were analyzed to obtain measures of the consistency and strength of the correlations. In most subjects, the bursts of electromyographic activity in one muscle were not consistently related to tremor activity in other affected muscles. Half the subjects exhibited moderate to strong correlations between thyroarytenoid muscle activity and the amplitude of the voice signal. Although the thyroarytenoid and cricothyroid muscles were always active during sustained phonation, half of the subjects did not activate either the thyrohyoid or the sternothyroid muscle during this task. The results of this study did not support the hypothesis that essential voice tremor is generated by a single central oscillator. Differences in the presence and timing of modulations in laryngeal muscle activity, as described in this study, may reflect clinically in the variable regularity and severity of vocal tremor.

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 ≤ 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.

Electromyographic Activity of Strap and Cricothyroid Muscles in Pitch Change

Roubeau B, Chevrie-Muller C, Lacau St Guily J. Electromygraphic activity of strap and cricothyroid muscles in pitch change. Acta Otolaryngol (Stockh) 1997; 117: 459-464.The EMG activity of the cricothyroid muscle (CT) and the three extrinsic laryngeal muscles (thyohyoid, TH; sternothyroid, ST, and sternohyoid, SH) were recorded throughout the voice range of one female and one male subject, both untrained singers. The voice range was examined using rising and falling glissandos (production of a sustained sound with progressive and continuous variation of fundamental frequency). Muscle activity was observed at various pitches during the glissandos. The strap muscle activity during the production of glissandos appears to be synergistic. At the lowest frequency, the CT is inactive but strap muscles (TH, ST, SH) are active. As frequency increases, strap muscle activity decreases while the CT controls frequency in the middle of the range. At higher frequencies the strap muscles once again become active. This activity might depend on the vocal vibratory mechanism involved. The role of the strap muscles at high pitches is a widely debated point but it seems that in some way they control the phenomena relevant to the rising pitch. The phasic-type strap muscle activity contrasts with the tonic-type activity of the CT. The CT closely controls the frequency, while the straps are not directly linked to the pitch but rather to the evolution of the frequency of voice production (speaking voice, singing voice, held notes, glissandos, trillo, vibrato, etc.).

Mechanism of glottic closure in a model of unilateral vocal fold palsy.

The effect of extrinsic laryngeal muscles on the position of the paralyzed vocal fold (VF) was analyzed in 13 adult human larynges. Fresh specimens were suspended within a specially constructed frame designed to reproduce the three-dimensional position of the VF, and to allow for simulation of laryngeal muscle action, in five successive experiments resembling: 1) complete vagal paralysis and contralateral adduction, 2) laryngeal elevation added, 3) vocal fold stretching added, 4) contralateral laryngeal tilting added, and 5) ipsilateral cricothyroid muscle activation added. We observed an incremental narrowing of the middle and posterior glottic gaps from 3.9 mm and 6.8 mm respectively in experiment 1 to 1.1 mm and 1.9 mm in experiment 5. Glottic closure in the final experiment was associated with rotation of the glottis to the "paralyzed" side in the axial plane, and contralateral laryngeal tilting in the coronal plane. We show that extrinsic laryngeal muscles can help to close a paralytic gap; crossing of the contralateral VF past the midline was not observed in any of the experiments.

An evaluation of laryngeal muscle activation in patients with voice tremor.

Eight patients with voice tremor were studied to characterize laryngeal muscle involvement. Electromyographic (EMG) recordings were made from intrinsic laryngeal muscles, simultaneously with some extrinsic laryngeal muscles, respiratory movement, and voice recordings during respiration, whisper, and phonation. Spectral measures were used to determine the tremor frequency and the prominence of spectral peaks in the EMG, respiratory and acoustic signals, while correlation coefficients were computed between pairs of tremulous EMG signals to measure the synchrony of tremor between muscles. The intrinsic laryngeal muscles were tremulous during respiration and speech, with the thyroarytenoid most often involved. Tremor was also detected in some of the extrinsic muscle recordings and the percentage of muscles with tremor was higher during phonation than during whisper or respiration. Time delays were found between tremor oscillations in laryngeal muscles. Because the thyroarytenoid was affected in all the patients studied, botulinum toxin injections may be beneficial in treatment of this voice disorder.

Multichannel Electromyographic Observations in Spasmodic Dysphonia Patients and Normal Control Subjects

Spasmodic dysphonia is primarily a disorder of vocalization. Increasing evidence, however, suggests that individuals with this disorder comprise a heterogeneous population characterized by abnormal motor control throughout the vocal tract. Multichannel simultaneous electromyography was performed on 11 spasmodic dysphonia patients and 10 normal awake subjects to investigate both the distribution of neuromotor abnormality within the vocal tract (eg, intrinsic and extrinsic laryngeal muscles, tongue, and palate) and the contribution of activation of higher central nervous system centers to observed abnormality. Experimental tasks ranged from vegetative (quiet breathing) to simple linguistic (short sentences). Digitized electromyographic signals were analyzed to compute the amplitude envelope and extract a set of parameters that represent amplitude characteristics. Electrode insertions were cross-validated by quantitative analysis of patterns of activation across selected reference tasks and by traditional qualitative methods. Between-group differences were found for measures of normalized median and peak token amplitudes. These differences are both task- and measure-dependent. Results highlight the complex and interactive effects of muscle, task, and quantitative measures on between-group differences.

Use of flexible fiberoptic laryngoscopy to assess patients with spasmodic dysphonia

<h2>Summary</h2> Flexible videolaryngoscopy was used to study 38 patients with spasmodic dysphonia, rating excessive activation of intrinsic laryngeal muscles, extrinsic muscle hyperfunction, tremor, and dystonic movements. Seventeen patients were also studied after unilateral botulinum toxin injection. Dysfunction varied greatly; however, discrete patterns could not be identified. Functional status correlated significantly with the total score of all pathologic indicators, but not with any single parameter. Botulinum toxin was highly effective in reducing intrinsic laryngeal muscle activation, but did not always improve tremor. Extrinsic laryngeal muscle hyperfunction was not significantly affected by the toxin