Three-dimensional anatomic characterization of the canine laryngeal abductor and adductor musculature

The biomechanics of vocal fold abduction and adduction during phonation, respiration, and airway protection are not completely understood. Specifically, the rotational and translational forces on the arytenoid cartilages that result from intrinsic laryngeal muscle contraction have not been fully described. Anatomic data on the lines of action and moment arms for the intrinsic laryngeal muscles are also lacking. This study was conducted to quantify the 3-dimensional orientations and the relative cross-sectional areas of the intrinsic abductor and adductor musculature of the canine larynx. Eight canine larynges were used to evaluate the 3 muscles primarily responsible for vocal fold abduction and adduction: the posterior cricoarytenoid, the lateral cricoarytenoid, and the interarytenoid muscles. Each muscle was exposed and divided into discrete fiber bundles whose coordinate positions were digitized in 3-dimensional space. The mass, length, relative cross-sectional area, and angle of orientation for each muscle bundle were obtained to allow for the calculations of average lines of action and moment arms for each muscle. This mapping of the canine laryngeal abductor and adductor musculature provides important anatomic data for use in laryngeal biomechanical modeling. These data may also be useful in surgical procedures such as arytenoid adduction.     

Myosin heavy chain composition in human laryngeal muscles.

OBJECTIVES: Myosin heavy chain (MHC) composition of human thyroarytenoid (TA), lateral cricoarytenoid (LCA), interarytenoid (IA), vocalis, posterior cricoarytenoid (PCA), and cricothyroid muscles were examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western bolt techniques. The presence of superfast MHC was also assessed using antibodies directed against the extraocular MHC. STUDY DESIGN: MHC protein was analyzed using fresh human laryngeal muscles. METHODS: Laryngeal muscles excised from cadavers were processed for SDS-PAGE. The composition of MHC isoforms was determined by densitometry. Western blot was carried out to identify specific bands. RESULTS: MHC types IIA and IIB are the predominant MHC components in human laryngeal muscles. The adductor muscles--TA, LCA, and IA--have a higher percentage of type IIB MHC and a lower percentage of type I when compared with the abductor--PCA. The rank file order for type IIB MHC composition (TA > LCA > or = IA > PCA) is the same in all specimens. A band migrating between type IIA and type I was observed in several specimens. Although similar to type IIL in rats, this atypical band did not react with anti-extraocular MHC antibody on Western blot. CONCLUSION: Characterization of laryngeal muscles determined by the composition of MHC is correlated with function and neural input. Human laryngeal muscle is characterized by a predominance of fast-type MHCs in laryngeal closing muscle and mixed fast-slow type MHCs in respiratory and phonatory muscle groups. Although an atypical myosin band similar to type IIL (superfast) MHC in rat was identified, it did not react with anti-extraocular MHC antibody.     

正常喉肌电生理特点研究

目的研究正常喉肌电生理特点，了解其与喉功能的关系。方法对36例正常受试者行喉肌电图检查，包括喉肌运动单位肌电测量、喉肌肌电干扰相波幅-转折数分析，并分析喉肌肌电与喉功能的关系。结果(1)各喉肌几乎无完全电静息，平静时仍有少量肌电位发放，环杓后肌和杓间肌甚至多呈轻度和中度干扰相。(2)喉肌轻度、中度、高度收缩时喉肌募集增强，肌电发放率增加，波幅增大，其中甲杓肌、环甲肌和环杓后肌肌电波幅和转折数增大幅度相似，而环杓侧肌和杓间肌肌电转折数增大明显较波幅显著。(3)各喉肌肌电均在其相应喉功能活动前活跃或抑制。结论各喉肌正常运动单位电位及不同收缩力量干扰相波幅-转折数量化分析等参数的正常值不相同，与其各自的解剖生理特点相关；各喉肌共同协作完成喉的各种正常的功能活动，是一个统一的整体，缺一不可。     

Thyroarytenoid muscle maintains normal contractile force in chronic vocal fold immobility.

BACKGROUND: Denervation of skeletal muscle typically results in irreversible denervation atrophy over time. This finding has generated controversy as to the efficacy of reinnervation procedures for chronic vocal fold immobility related to recurrent laryngeal nerve injury. OBJECTIVE: To test the hypothesis that chronic vocal fold immobility after recurrent laryngeal nerve injury does not result in diminished maximal isometric force generation in the thyroarytenoid muscle. STUDY DESIGN: Adult random-bred cats underwent either unilateral laryngeal denervation (n = 6) or sham surgery (n = 6). After 6 months, videolaryngoscopy was performed followed by in vitro measurement of maximal isometric tetanic force produced by the thyroarytenoid muscle. RESULTS: All animals in the denervation group showed right vocal fold paralysis after the initial denervation operation; none of these animals had return of appropriately phased movement with respiration. Four had intermittent disorganized twitching movements. One had these movements plus an occasional weak adduction, and one had no movement. Normal vocal fold mobility was observed in 6 of 6 animals undergoing sham surgery. The maximal isometric tetanic force measured from the thyroarytenoid muscle in the sham group was 438 mN (+/-92 mN standard deviation [SD]). The maximal isometric tetanic force measured from the thyroarytenoid muscle in the chronically immobile group was 405 mN (+/-107 mN SD). Differences were not statistically significant. CONCLUSION: Maximal isometric force in the thyroarytenoid muscle is not diminished in chronic vocal fold immobility after recurrent laryngeal nerve injury. We conclude that the possibility for restoration of contractile force to the chronically immobile thyroarytenoid muscle exists. This finding supports the pursuit of reinnervation procedures in the treatment of chronic vocal fold immobility.     

Three-dimensional laryngeal model for planning of laryngeal framework surgery

CONCLUSION: The three-dimensional prototype model was useful for planning of laryngeal framework surgery. OBJECTIVE: To discuss the usefulness of a three-dimensional laryngeal model for laryngeal framework surgery. MATERIALS AND METHODS: A three-dimensional laryngeal model was created based on the postoperative helical computed tomography (CT) data of the larynx (case 1) which underwent lateral cricoarytenoid muscle (LCA) pull surgery. LCA pull surgery is a kind of arytenoid adduction for unilateral vocal cord paralysis. A three-dimensional model of case 1 larynx was prototyped using a selective laser sintering method. In case 1, the patient's voice did not improve after LCA pull surgery. The three-dimensional model revealed that the original surgical procedure was not appropriate to obtain optimal arytenoid adduction. According to the analysis of this three-dimensional model, we changed the surgical approach and performed this new refined LCA pull surgery on another patient with unilateral vocal cord paralysis (case 2). RESULTS: We were able to pull LCA precisely in case 2. Three-dimensional CT of case 2 after refined LCA pull surgery allowed the correct pulling of LCA and complete adduction of arytenoid. The postoperative voice improved remarkably.     

Three-dimensional laryngeal model for planning of laryngeal framework surgery

Conclusion. The three-dimensional prototype model was useful for planning of laryngeal framework surgery. Objective: To discuss the usefulness of a three-dimensional laryngeal model for laryngeal framework surgery. Materials and methods. A three-dimensional laryngeal model was created based on the postoperative helical computed tomography (CT) data of the larynx (case 1) which underwent lateral cricoarytenoid muscle (LCA) pull surgery. LCA pull surgery is a kind of arytenoid adduction for unilateral vocal cord paralysis. A three-dimensional model of case 1 larynx was prototyped using a selective laser sintering method. In case 1, the patient's voice did not improve after LCA pull surgery. The three-dimensional model revealed that the original surgical procedure was not appropriate to obtain optimal arytenoid adduction. According to the analysis of this three-dimensional model, we changed the surgical approach and performed this new refined LCA pull surgery on another patient with unilateral vocal cord paralysis (case 2). Results. We were able to pull LCA precisely in case 2. Three-dimensional CT of case 2 after refined LCA pull surgery allowed the correct pulling of LCA and complete adduction of arytenoid. The postoperative voice improved remarkably.     

Control of vocal loudness in young and old adults.

This study examined the effect of aging on respiratory and laryngeal mechanisms involved in vocal loudness control. Simultaneous measures of subglottal pressure and electromyographic (EMG) activity from the thyroarytenoid (TA), lateral cricoarytenoid (LCA), and cricothyroid (CT) muscles were investigated in young and old individuals while they attempted to phonate at three loudness levels, "soft," "comfortable," and "loud." Voice sound pressure level (SPL) and fundamental frequency (F ) measures were also obtained. Across loudness conditions, subglottal pressure levels were similar for both age groups. Laryngeal EMG measures tended to be lower and more variable for old compared with young individuals. These differences were most apparent for the TA muscle. Finally, across the three loudness conditions, the old individuals generated SPLs that were lower overall than those produced by the young individuals but modulated loudness levels in a manner similar to that of the young subjects. These findings suggest that the laryngeal mechanism may be more affected than the respiratory system in these old individuals and that these changes may affect vocal loudness levels.     

Configuration of the glottis in laryngeal paralysis. II: Animal experiments

It is widely believed that in isolated recurrent laryngeal nerve paralysis, the paralyzed vocal fold assumes a median or paramedian position, due to the action of the cricothyroid muscle. A review of the literature reveals that support for this theory is not conclusive and, in particular, experiments indicate that the cricothyroid muscle does not appreciably affect vocal fold position in acute paralysis. The research in this study compares the configuration of the glottis in chronic unilateral recurrent laryngeal nerve paralysis in cats, with and without concomitant denervation of the cricothyroid muscle. Results indicate that vocal fold position is not determined by the cricothyroid muscle. Incomplete denervation of intrinsic laryngeal muscles as well as synkinetic reinnervation appear to be significant factors in determining vocal fold position in chronic laryngeal paralysis.     

Motion-specific laryngeal reinnervation using muscle-nerve-muscle neurotization

There is no current treatment method that can reliably restore physiologic movement to a paralyzed vocal fold. The purposes of this study were to test the hypotheses that 1) muscle-nerve-muscle (M-N-M) neurotization can be induced in feline laryngeal muscles and 2) M-N-M neurotization can restore movement to a paralyzed vocal fold. Muscle-nerve-muscle neurotization can be defined as the reinnervation of a denervated muscle via axons that are induced to sprout from nerves within an innervated muscle and that then traverse a nerve graft interposed between it and the target denervated muscle. A paralyzed laryngeal muscle could be reinnervated by axons from its contralateral paired muscle, thus achieving motion-specific reinnervation. Eighteen adult cats were divided into sham, hemilaryngeal-denervated, and M-N-M-reinnervated thyroarytenoid muscle groups. Five of the 6 reinnervated animals had histologic evidence of axons in the nerve graft, 4 of the 6 had evoked electromyographic evidence of crossed reinnervation, and 1 of the 6 had a return of appropriately phased adduction. This technique has great potential and should be further investigated.     

Laryngeal reinnervation for unilateral traumatic recurrent laryngeal nerve injuries]

OBJECTIVE: To investigate 5 procedures of laryngeal reinnervation for unilateral vocal cord paralysis induced by traumatic recurrent laryngeal nerve injury. METHODS: 35 cases were selected for our study, all patients had unilateral recurrent laryngeal nerve injury, including 8 for nerve decompression, 6 for end to end anastomosis of recurrent laryngeal nerve, 16 for main branch of ansa cervicalis anastomosis to recurrent laryngeal nerve, 3 for nerve muscular pedicle and 2 for nerve implantation. All cases have been subjected to preoperative and postoperative voice recording, acoustic analysis, videolaryngoscopy, strobscopy and electromyography. RESULTS: It is found the adductory and abductory motion of the vocal cord restored in 5 cases with less than 4 months course who received nerve decompression. Although functional motion of vocal cord was not seen in two patients who received nerve decompression with a course longer than 4 months and one less than 4 months, and in all cases who received ansa cervicalis anastomosis and end to end anastomosis of recurrent laryngeal nerve, these procedures resulted in medialization of vocal cord and the mass and tension of the reinnervated vocal cord may become much the same as the contralateral normal vocal cord, thus resuming symmetric vibration of the vocal cords and physiological phonation. Nerve muscular pedicle technique and nerve implantation enabled adductory muscles to be reinnervated, thus improving severe hoarseness, but they didn't restore normal voice. CONCLUSIONS: (1) Nerve decompression seems to be the best procedure in laryngeal reinnervation; (2) Main branch of ansa cervicalis technique raises satisfactory reinnervation of adductor muscles; (3) Selection of the laryngeal reinnervation protocols should depend on the course, severity and type of nerve injury.     

Unilateral vocal fold adductor paralysis after tracheal intubation

Vocal fold immobility is a relatively rare complication that can occur after tracheal intubation. Differential diagnoses include a rare clinical entity called unilateral vocal fold adductor paralysis in which only branches entering the thyroarytenoid and lateral cricoarytenoid muscles of the recurrent laryngeal nerve become paralyzed. Computed tomography and laryngeal electromyography are required to distinguish this condition from others such as cricoarytenoid dislocation/subluxation. Here, we describe two patients who developed vocal fold adductor paralysis after intubation. Patient 1 was a 56-year-old man who underwent living-donor liver transplantation and was extubated on day 7 after surgery. Patient 2 was a 52-year-old man who received life support measures including intubation due to ventricular fibrillation, and was extubated two days later. Both were hoarse soon after extubation. Endoscopic laryngeal examination revealed normal abduction and insufficient adduction of paralyzed vocal folds. Computed tomography ruled out cricoarytenoid dislocation/subluxation and laryngeal electromyography confirmed unilateral vocal fold adductor paralysis. Laryngologists should consider this rare pathogenesis.     

Anatomy and fiber type composition of human interarytenoid muscle

Intrinsic laryngeal muscle investigations, especially those of the interarytenoid (IA) muscle, have been primarily teleologically based. We determined IA muscle anatomy and histochemical and immunohistochemical classification of extrafusal and intrafusal (muscle spindle) fibers in 5 patients. Extrafusal fibers were oxidative type I and glycolytic types IIA and IIX. Intrafusal fibers of muscle spindles were identified by the presence of tonic and neonatal myosin. The results demonstrate that the IA muscle has a phenotype similar to that of limb skeletal muscle. Myosin coexpression, the absence of intrafusal fibers, and fiber type grouping were unusual features found previously in the thyroarytenoid and posterior cricoarytenoid muscles, but they were not present in the IA muscle. These findings lead to the conclusion that the IA muscle has functional significance beyond its assumed importance in maintaining vocal fold position during phonation. The presence of spindles demonstrates differences in motor control as compared to the thyroarytenoid and posterior cricoarytenoid muscles. Further, extrafusal fiber characteristics implicate IA muscle involvement in muscle tension dysphonia and adductor spasmodic dysphonia. Given the unique physiologic characteristics of the human IA muscle, further research into the role of the IA muscle in voice disorders is warranted.     

A new procedure of arytenoid adduction combined with type I thyroplasty under general anesthesia using a laryngeal mask

Laryngeal framework surgery is usually performed under local anesthesia. However, some patients are unable to tolerate extended surgery. A case of an 82-year-old woman who underwent medialization thyroplasty and arytenoid adduction of direct lateral cricoarytenoid (LCA) muscle pulling at the same time under general anesthesia using a laryngeal mask is reported. Endoscopic observation through the laryngeal mask allows direct visual control of the vocal cord. The LCA pulling method does not touch the posterior border of the thyroid cartilage so that the laryngeal mask does not disturb the arytenoid adducts.     

舌骨上肌与喉内肌的同步肌电生理实验研究

目的对犬的舌骨上肌（二腹肌前腹、后腹,茎突舌骨肌,下颌舌骨肌和颏舌骨肌）与喉内肌（环杓侧肌和环杓后肌）进行同步肌电图研究。方法检测13只犬同步肌电图。结果①呼吸时环杓侧肌在呼气相放电,余各肌在吸气相放电。深呼吸时诸肌放电强度增加。②吞咽时诸肌和环杓侧肌呈同步放电。环杓后肌肌电抑制,间歇期可见肌电位发放。③发音时二腹肌前腹、后腹和环杓侧肌呈同步性密集型放电,环杓后肌在发音过程中持续放电,动作电位出现时间较迟。茎突舌骨肌和颏舌骨肌无明显肌电活动。结论①发音及吞咽时下颌舌骨肌与环杓侧肌同步且相似,可作为重建声门内收功能的备选肌肉;②吸气时颏舌骨肌与环杓后肌同步且相似,可作为重建声带外展功能的备选肌肉。     

Artificial restoration of voice. I: Experiments in phonatory control of the reinnervated canine larynx

Coordinated electronic pacing of implanted nerve pedicles into paralyzed laryngeal muscles has allowed selective dynamic control of abduction, adduction, and elongation of the vocal cords. Modifications of the original circuit in a cervical muscle model has added fine tuning to basic "all-or-none" pacing. Rehabilitation of phonation illustrated the sophisticated nature of voice and the need for restoration of fine tuning. Five mongrel dogs received nerve-muscle pedicles into the thyroarytenoideus, cricothyroideus, and posterior cricothyroideus after denervation of one hemilarynx. Following appropriate reinnervation time, pedicles and intact recurrent laryngeal nerves were injected with currents of variable amplitudes and pulse widths to achieve graded vocal fold control while air was blown intratracheally towards the glottic chink. Videoscopic and spectral analyses indicated that artificial phonation could be restored to frequencies measured in the normal state. These experiments suggested that rehabilitation of the impaired voice by servocontrol might eventually be feasible.     

Laryngeal Electromyography in the Management of Vocal Cord Mobility Problems in Children

Objectives To evaluate the efficacy and clinical usefulness of laryngeal electromyography (EMG) in the evaluation and management of vocal cord mobility problems in children; and to determine the ability of laryngeal EMG to differentiate vocal fold fixation versus paralysis. Study Design Case‐series review of 8 children with vocal cord immobility who underwent laryngeal EMG. Methods Eight children with bilateral vocal fold immobility underwent microlaryngoscopy and electromyography. Bipolar concentric needle electrodes were used and implanted separately into both posterior cricoarytenoid (PCA) and both thyroarytenoid (TA) muscles. EMG activity was recorded during spontaneous ventilation under a light plane of anesthesia with propofol. EMG activity was correlated with the phases of the respiratory cycle. Results Three patients had evidence of normal EMG activity with PCA activity peaking during early inspiration. Maximal TA activity occurred expiration. These patients were assumed to have vocal fold fixation. Two of these 3 patients underwent laryngotracheoplasty (LTP) with posterior glottic expansion with costal cartilage. One is being considered for LTP in the future. Five patients had abnormal EMG activity and remain tracheotomy‐dependent. Four patients exhibited synkinetic activity with peak PCA activity during expiration and peak TA activity during expiration. Two patients had both fixation and unilateral vocal cord paralysis. One was successfully decannulated after posterior graft LTP and the other is planned for the future. Conclusions Electromyography, which differentiates paralysis from fixation, is a useful diagnostic tool in the evaluation of children with vocal cord immobility.     

Restoring vocal fold movement after transection and immediate suturing of the recurrent laryngeal nerve with local application of basic fibroblast growth factor: an experimental study in the rat

OBJECTIVE: To evaluate the effects of basic fibro-blast growth factor (bFGF) on the recovery of vocal fold movement and the attenuation of laryngeal muscle atrophy after transection of the recurrent laryngeal nerve (RLN). STUDY DESIGN: Quantitative assessment of vocal fold movement using the video cassette recorder (VCR) image-analysis method and histologic examination of the laryngeal muscle. METHODS: Fifty-eight Wistar rats underwent RLN transection and one of the following three procedures: 1) transection of the RLN alone (transection group, n = 18), 2) suture of the nerve stumps followed by local administration of phosphate-buffered saline (PBS) solution using an osmotic pump (PBS group, n =20), or 3) suture of the nerve stumps followed by local administration of bFGF (FGF group, n = 20). Vocal fold movements were recorded with VCR by way of a rigid endoscope, and the VCR images were analyzed on a computer. Histologic changes in the thyroarytenoid (TA) muscle were evaluated by measuring the cross-sectional area of the muscle and average size of muscle fibers. RESULTS: In the transection group, vocal fold movement did not recover, and atrophy of the TA muscle gradually progressed after sectioning the nerve. In contrast, vocal fold movement as assessed by VCR image-analysis recovered in some cases in the immediate suturing groups, more markedly in the FGF group (34.1 +/- 29.1%) than in the PBS group (5.5 +/- 7.9%) (P <.05). Histologically, atrophy of the laryngeal muscle was significantly attenuated by the local administration of bFGF. CONCLUSION: bFGF facilitates regeneration of the transected RLN and attenuation of intrinsic laryngeal muscle atrophy, thereby restoring laryngeal function.     

Functional laryngeal abduction following reimplantation of the recurrent laryngeal nerves

Functional reinnervation was established in a patient following complete laryngo-tracheal separation with avulsion of both recurrent laryngeal nerves. Following reattachment of the larynx to the trachea, the severed stumps of the recurrent laryngeal nerves were implanted into the laryngeal abductors (the posterior crico-arytenoid muscles). One year later the patient had good abduction and adduction of her vocal cords. The abduction is thought to be a result of reinnervation by the recurrent laryngeal nerves, the adduction due to the action of crico-thyroid muscle whose innervation was undisturbed by the original injury.     

Echo-Planar Magnetic Resonance Imaging of Deglutitive Vocal Fold Closure: Normal and Pathologic Patterns of Displacement

Abnormalities of vocal fold closure during deglutition predispose to aspiration due to impairment of airway protection. Conventional assessment of deglutitive vocal fold motion with laryngoscopy does not permit visualization through a complete adduction-abduction cycle. We determined spatiotemporal patterns of deglutitive vocal fold adduction through echo-planar magnetic resonance imaging in 15 normal volunteers and 6 patients with vocal fold paralysis. In normal volunteers, deglutitive vocal fold adduction was synchronized with laryngeal elevation, with complete vocal fold closure at the apex. Patients with unilateral vocal fold paralysis demonstrated reduced elevation and medial movement of the involved vocal fold. At maximal laryngeal elevation the uninvolved vocal fold attained a position superior to the paralyzed fold, resulting in level differences and an interglottic gap. Patients with bilateral vocal fold paralysis demonstrated reduced elevation and medial movement of both vocal folds. These findings indicate that normal and abnormal patterns of vocal fold displacement can be distinguished noninvasively through the use of echo-planar imaging. Laryngoscope, 106:568-572, 1996     

Four cases of dysosmia with no vocal cords adduction during sniff (laryngeal dysosmia)

The author first reported that the vocal cords adduct during sniff. This movement was observed both in normal and in anosmic subjects. In this paper four cases of dysosmia with no adduction of vocal cords during sniff was reported. The pattern of their olfactometry showed same tendencies, normal detective thresholds and inability of recognition and/or very low recognition threshold. With the observations and referenced articles, the author concluded that the vocal cord's adduction during sniff is a specific movement when the larynx concern with olfaction, and that the adductory movements is related to olfactory recognition. It was thought that the orbital cortex integrates the afferent stimulations from the larynx during sniff and olfaction from the nose. The author concluded also there exists these reported kind of dysosmia with no vocal cord adductory movement.