A new surface electrode for recording from the posterior cricoarytenoid muscle

A new pharyngeal surface electrode for recording posterior cricoarytenoid muscle activity through the hypopharyngeal mucosa has been evaluated. The electrode was passed through one nasal passage into the hypopharynx. Correct electrode location was verified by increased activity during inhalation, with decreased activity during phonation. The procedure was evaluated in 45 subjects, 10 normal speakers and 35 patients with dysphonia. Accurate recordings were obtained in 25 subjects (56%). Problems encountered were lack of pharyngeal descent, electrode dysfunction, and signal interference due to phonatory vibration or interarytenoid activity. Signal validity was evaluated in four normal speakers with accurate electrode placement. Significant (p less than or equal to 0.001) increases in PCA activity occurred during tasks requiring vocal fold abduction. The electrode proved to be a useful, noninvasive clinical tool for recording PCA activity in some patients.     

Electromyography of the cricoarytenoid muscle in the unsedated patient using the zoom-endoscope (author's transl)]

The EMG enables diagnosis, follow-up and prognosis of vocal cord palsy as well as indications for surgery. Using the zoom-endoscope of von Stuckrad electromyography of the larynx can be performed under topical anaesthesia. With a specially designed instrument the needle electrode can be transorally applied exactly into the posterior cricoarytenoid muscle and into any other muscle of the larynx. As the patient can follow instructions the voluntary muscle activity can be observed on the monitor and stored on tape during inspiration, exspiration and phonation. Replay and electronic summation are possible.     

Laryngeal electromyographic activity in adductor and abductor spasmodic dysphonia

Vocal symptoms in spasmodic dysphonia (SD) range from strain-strangle phonation and glottal-stop phonatory breaks of adductor SD to breathy phonation and aspirate phonatory breaks of abductor SD. Many SD subjects show both symptom types. Heterogeneity in vocal symptoms contributes to controversy surrounding the etiology(s) of SD. Acoustic/perceptual analyses of vocal symptoms are inconclusive in resolving this controversy. This investigation moves the search for distinguishing features of adductor and abductor SD to the level of neuromuscular control and analysis of intrinsic laryngeal muscle (adductor and abductor) activity. Subjects rated perceptually as primarily adductor or abductor SD sustained production of vegetative gestures and isolated speech sounds (/i/ and /s/). Qualitative and quantitative analyses of electromyographic signals recorded from thyroarytenoid (TA) failed to differentiate SD subjects by symptom type. Analysis of TA and posterior cricoarytenoid (PCA) activity in one abductor SD revealed high levels in both muscles during production of the voiced vowel. Data suggest that a possible explanation for symptom heterogeneity in SD is the relation between disrupted neuromotor input to laryngeal muscles and reflexive or conscious compensations constrained by laryngeal biomechanics.     

Arytenoid adduction: controlling vertical position

In flaccid laryngeal paralysis, the vocal process (VP) is displaced laterally and superiorly. The arytenoid adduction procedure (AA) moves the VP medially and caudally, closing the glottic gap. However, clinical evidence suggests that the VP is more caudal after AA than in physiological phonation. The neurally intact arytenoid is supported by tonic and phonatory activity of the posterior cricoarytenoid muscle (PCA). We hypothesize that a posterior anchoring suture could replace PCA support, achieving a more natural VP location. Cadaver larynges were scanned with computed tomography at rest and after AA, alone or in combination with a second arytenoid suture anchored to either the posterior midline cricoid (PC) or the inferior thyroid cornu (IC). Each posterior suture reduced caudal displacement of the VP during AA, but the glottic gap was wider with the PC suture. In 3 patients undergoing AA for laryngeal paralysis, the IC suture improved arytenoid posture and voice quality.     

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。     

Posterior cricoarytenoid myoplasty with medialization thyroplasty in the management of refractory abductor spasmodic dysphonia

Of the approximately 100,000 Americans with primary (idiopathic) laryngeal dystonia, 10% to 15% are thought to havethe abductor form. Botulinum A toxin injected into the posterior cricoarytenoid muscle and/or cricothyroid muscle has been employed as the "gold standard" for therapeutic management; however, successful results are significantly less frequent than with injections for the adductor form. This report describes a new phonosurgical procedure, posterior cricoarytenoid myoplasty with medialization thyroplasty, designed for these refractory patients. Posterior cricoarytenoid myoplasty with medialization thyroplasty has been performed on 3 patients with abductor laryngeal dystonia. All patients had failed at least 5 previous botulinum A injections to the posterior cricoarytenoid and cricothyroid muscles. All patients underwent preoperative and 3 postoperative (2 weeks, 3 months, and 1 year) phonatory analyses. Analysis consisted of recording an aloud reading of a standard passage while a blinded trained speech pathologist counted prolonged voiceless consonants. The patients also completed a satisfaction survey at 1 year. The results demonstrated significant, long-lasting, uniform reduction in breathy breaks in all subjects. The participants all judged their symptoms as greatly improved. Bilateral procedures may be necessary, but should be staged to prevent possible airway compromise. When applied appropriately, posterior cricoarytenoid myoplasty with medialization thyroplasty is a viable tool in the management of refractory abductor laryngeal dystonia.     

Laryngeal pacemaker using a temperature sensor in the canine

With the use of a temperature sensor that would detect temperature changes during the respiratory cycle in the pharynx, electrical stimulation of the posterior cricoarytenoid muscle was achieved in dogs whose recurrent laryngeal nerves were artificially paralyzed. Due to the temperature difference between inspiratory and expiratory air flow, a trigger pulse was generated at the beginning of inspiration. The stimulation pulse following the trigger pulse stimulated the electrodes inserted into the posterior cricoarytenoid muscles. In all five canines, obvious abduction of the vocal folds synchronized with inspiration was observed during electrical pacing.     

The three bellies of the canine posterior cricoarytenoid muscle: Implications for understanding laryngeal function

The posterior cricoarytenoid (PCA) muscle is known to be active during phonation and respiration. The presence of muscle compartments (bellies) that might subserve these functions was investigated in the canine PCA by anatomical dissection and muscle fiber histochemistry. Five PCA muscles were microdissected and the origins and insertions of all muscle bundles were recorded. An additional six PCA muscles were frozen, sectioned, and stained for adenosine triphosphatase (ATPase) activity. The total number of fast- and slow-twitch fibers were counted and their proportion was determined for each region of the muscle. The PCA muscle was found to contain three distinct neuromuscular compartments. The vertical compartment is oriented at 24 degrees from true vertical, inserts on the lateral aspect of the muscular process of the arytenoid, and is composed of 65% type 2 (fast) muscle fibers. The oblique is oriented at 44 degrees from vertical, inserts on the top of the muscular process of the arytenoid, and is composed of 77% type 2 muscle fibers. The horizontal is oriented at 63 degrees from vertical, inserts on the medial aspect of the muscular process of the arytenoid, and is composed of 59% type 2 muscle fibers. The cricoarytenoid joint is capable of three arcs of motion and the physical arrangement of each compartment appears to correspond to each of these motions. Moreover, the histochemical profiles show that the activity of the three bellies is quite different. These results suggest that the different compartments of the PCA perform distinctive motions during phonation and inspiration.     

Involuntary expiratory phonation as a dose-related consequence of L-dopa therapy in a patient with Parkinson's disease

We report a case of involuntary phonation caused by abnormal vocal cord movements during expiration in a patient with Parkinson's disease. A 60-year-old woman had been treated for parkinsonism at the outpatient clinic of the Department of Neurology since August 1999. She began to groan involuntarily in the daytime in September 2001. She could not eat well while groaning. Stridor was not noted during sleep at night. Endoscopic examination of the larynx revealed insufficient abduction of the bilateral vocal cords, although the glottis was not so small as to cause stridor during inspiration. During expiration, however, the vocal cords adducted, resulting in the involuntary production of voice. Electromyography showed an increase in the activity of the thyroarytenoid and lateral cricoarytenoid muscles. This muscle activity was further enhanced during inspiration. The involuntary phonation disappeared when the patient's dose of L-dopa was decreased, although she had a decrease in her systemic mobility as well. When the dose of L-dopa was increased to the therapeutic level, involuntary phonation recurred, and her voluntary systemic activity improved. In the present case, it was considered that excessive dopaminergic denervation occurred in the nerve innervating the laryngeal adductors. Involuntary voice appeared to be produced by hypertonus of the laryngeal adductors because of a lowering in the threshold level for L-dopa, even though the drug was administered at the usual dose.     

Arytenoid motion evoked by regional electrical stimulation of the canine posterior cricoarytenoid muscle

Anatomical studies have demonstrated that the posterior cricoarytenoid muscle in the dog is composed of three bellies. These bellies are termed vertical, oblique, and horizontal on the basis of their orientation. The purpose of this study was to show whether each of these bellies can move the vocal fold in different ways. Ten anesthetized dogs underwent laryngectomies while paralyzed with curare. The posterior cricoarytenoid muscles were then exposed by dissecting the overlying esophageal mucosa. Electrical stimulation was applied to each belly, and the motion of the arytenoid cartilage was measured. Because the oblique belly overlies the vertical belly, they were usually stimulated together. It was found that the vertical and oblique bellies rock the arytenoid backwards while sliding it laterally, thus causing a maximal dilation of the airway. The horizontal belly caused a swiveling motion of the arytenoid. It is proposed that the vertical and oblique bellies normally cause vocal fold abduction during respiration, while the horizontal belly primarily is used to adjust finely the position of the vocal process during phonation. Because the human posterior cricoarytenoid is also composed of separate bellies it, too, may have distinct functions.     

Lupenendoskopische Elektromyographie des Musculus crico-arytaenoideus dorsalis (Posticus) am wachen Patienten

Summary The EMG enables diagnosis, follow-up and prognosis of vocal cord palsy as well as an indication for surgery. Using the zoom-endoscope by v. Stuckrad the EMG can be performed in local anesthesia. With a specially designed instrument the needle electrode can be transorally applied exactly in the posterior cricoarytenoid muscle as well as in other muscles of the larynx. As the patient can follow instructions both voluntary and spontaneous activity can be recorded under visual and acoustic control during inspiration, phonation and exspiration on a tape. Thus replay, control examination and electronic summation is possible.     

Recurrent nerve/ansa cervicalis nerve anastomosis: a treatment alternative in unilateral recurrent nerve paralysis.

Sectioning of the right recurrent nerve was done in 5 mongrel dogs under general anaesthesia. The distal stump was anastomosed with the ansa cervicalis nerve branch to the sternothyroid muscle. Three to 5 months later the vocal cord movements during light and very light anaesthesia were videorecorded. Under light anaesthesia contraction and medial bulging of the reinnervated right vocal cord occurred in 4 of the dogs. Under very light anaesthesia there was also some adduction of the right vocal cord in these 4 dogs. The right recurrent nerve was then sectioned proximally to the anastomosis and stimulated electrically. In all 5 dogs we observed that electrical stimulation produced a strong adduction of the right vocal cord. Histochemistry of the right vocal and posterior cricoarytenoid muscles showed that reinnervation had taken place. The study indicates that in cases of unilateral vocal cord paralysis an anastomosis between the ansa cervalalis and the recurrent nerve will result in improved phonatory function of the affected vocal cord.     

Long-term implantation of a system of electrical stimulation of paralyzed laryngeal muscles in dogs

Electrical stimulation of the posterior cricoarytenoid muscle, synchronized with inspiration, was achieved in dogs utilizing a radio frequency stimulus triggered by a chest wall expansion transducer. This system brings about abduction of the paralyzed vocal cord for the entire duration of inspiration, which allows a normal flow of air through the larynx. The implantable part of that system was tested successfully in chronic experiments (up to 11 months) in dogs with experimental paralysis of the recurrent laryngeal nerve. We feel that the system may be suitable for pacing the paralyzed human larynx.     

Recurrent Nerve/Ansa Cervicalis Nerve Anastomosis: A Treatment Alternative in Unilateral Recurrent Nerve Paralysis

Sectioning of the right recurrent nerve was done in 5 mongrel dogs under general anaesthesia. The distal stump was anastomosed with the ansa cervicalis nerve branch to the sternothyroid muscle. Three to 5 months later the vocal cord movements during light and very light anaesthesia were videorecorded. Under light anaesthesia contraction and medial bulging of the reinnervated right vocal cord occurred in 4 of the dogs. Under very light anaesthesia there was also some adduction of the right vocal cord in these 4 dogs. The right recurrent nerve was then sectioned proximally to the anastomosis and stimulated electrically. In all 5 dogs we observed that electrical stimulation produced a strong adduction of the right vocal cord. Histochemistry of the right vocal and posterior cricoarytenoid muscles showed that reinnervation had taken place. The study indicates that in cases of unilateral vocal cord paralysis an anastomosis between the ansa cervicalis and the recurrent nerve will result in improved phonatory function of the affected vocal cord.     

Reconstruction of laryngeal function for recurrent laryngeal nerve paralysis: historical view, advancement of latest investigations and a preliminary experiment.

Historical investigations of the functional restoration for recurrent laryngeal nerve paralysis are reviewed and some advancement in recent studies are introduced. A preliminary experiment is reported in which the ansa hypoglossi and the sternothyroid muscle pedicle was implanted into the denervated posterior cricoarytenoid muscle in dogs. From these experiments we have concluded that the ansa hypoglossi and sternothyroid muscle pedicle, which has been shown to transmit efferent inspiratory bursts, is capable of restoring function to the paralyzed posterior cricoarytenoid muscle in some dogs.     

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.     

Age-related changes in the neuromuscular junctions in the human posterior cricoarytenoid muscles: a quantitative study.

The posterior cricoarytenoid muscle is unique histochemically, ultrastructurally, and functionally. It has been suggested that the posterior cricoarytenoid muscle undergoes early aging. Aging in peripheral nerves has been reported to resemble a "dying back" neuropathy in that the most severe and earliest age-related changes occur at the most distal levels of the nerve fibers. The lengths and terminal axonal branching of neuromuscular junctions in 17 human posterior cricoarytenoid muscles aged 4 days to 95 years were determined. Both neuromuscular junction lengths and the numbers of axonal terminal branches in the very young group differed significantly from values in two older groups. In contrast to results reported for some other muscles, there was no significant age-related change in these parameters in the posterior cricoarytenoid muscle during adult life. This difference may be related to the repetitive contraction of the posterior cricoarytenoid muscle.     

一侧膈神经上根选择性神经再支配环杓后肌的实验研究

目的 探讨一侧膈神经上根选择性神经再支配环杓后肌的可行性和有效性.方法 8只健康雄性青年Beagle犬作为实验动物,全麻下切断Beagle犬左侧膈神经上根与左侧喉返神经,两断端通过游离神经桥接的方式吻合,并将同侧喉返神经内收肌支切断并植入同侧环杓后肌中;右侧不做任何处理,作为正常对照侧.于手术前、神经修复术后即刻、术后6个月分别行电子喉镜和喉肌电图检查,在最后一次检查后处死动物,取双侧环杓后肌和喉内段喉返神经行组织学检查并与对侧比较.结果 术前8只犬的双侧声带运动正常,术后即刻左侧声带固定,术后6个月均恢复了吸气性外展运动.术前8只犬双侧环杓后肌均能记录到自发肌电位,并引出诱发电位;术后即刻左侧环杓后肌呈电静息,未记录到诱发电位;术后6个月均能记录到自发肌电位,并引出诱发电位,而且两种电位幅度分别与术前比较差异均无统计学意义(均为P>0.05).环杓后肌Masson染色示两侧肌肉纤维相对截面积、胶原纤维相对截面积、肌肉/胶原纤维截面积比差异均无统计学意义(均为P>0.05).喉内段喉返神经甲苯胺蓝染色后示神经纤维分布较均匀密集,且左右两侧喉返神经有髓神经纤维数量差异无统计学意义(P>0.05).结论 左侧膈神经上根选择性神经再支配环杓后肌能有效避免神经错向再生,恢复声带的生理性外展运动.     

Respiratory rhythmically regulated electrical stimulation of paralyzed laryngeal muscles

Electrical stimulation of the posterior cricoarytenoid muscle, synchronized with inspiration, was achieved in dogs, utilizing a radio frequency stimulus triggered by a chest wall expansion transducer. This system brings about the abduction of the paralyzed vocal cord for the entire duration of inspiration, which allows a normal flow of air through the larynx. The stimulation system could be tested successfully in actual experiments in dogs with artificial paralysis of the recurrent laryngeal nerve. Its effectiveness could be proved through observation of the vocal cord movements (photographic documentation) and recording subglottic pressure variations. Transmission of stimulation energy is effected by electrical induction.     

Effects of cricothyroid muscle contraction on laryngeal resistance and glottic area

To determine the functional significance of the cricothyroid muscle (CT) in respiration, laryngeal resistance was measured in anesthetized dogs, along with electromyographic activity of the posterior cricoarytenoid muscle (PCA) and CT. In two dogs the larynx was videotaped simultaneously via a telescope. Increased CT activity was induced by airway occlusion or hypercapnia. Observations were carried out before and during cold blockade of the recurrent laryngeal nerve (RLN) or the nerve to the CT (external branch of the superior laryngeal nerve [Ext SLN]). Paralysis of the CT had no effect on laryngeal resistance or glottic area, even at very high levels of CT activity. Blockade of the RLN increased inspiratory resistance, but did not have a significant effect on expiratory resistance. Electrical stimulation of the Ext SLN produced tetanic CT contraction, which increased laryngeal resistance in both inspiration and expiration. This was true even at very high levels of PCA activity. These results indicate that although artificially induced CT contraction markedly affects laryngeal resistance, physiologic levels of respiratory activity do not have a significant effect.