Intrinsic laryngeal muscle reinnervation using the muscle-nerve-muscle technique

OBJECTIVES: This study was performed to investigate the muscle-nerve-muscle reinnervation technique in the larynx, in which a nerve conduit implanted into an innervated muscle conducts axonal sprouting into a denervated muscle while maintaining function of the donor muscle. METHODS: In this study, the muscle-nerve-muscle technique was used to direct superior laryngeal nerve axons to reinnervate intrinsic laryngeal muscles by implanting the recurrent laryngeal nerve stump into the cricothyroid muscle in 8 dogs. In 4 of the dogs, the recurrent laryngeal nerve trunk to the adductor muscles was divided so that all axonal sprouting was directed to the posterior cricoarytenoid muscle. Six-month electromyography data were obtained from 6 of the 8 dogs. RESULTS: All 6 dogs showed evidence of successful reinnervation of the thyroarytenoid or posterior cricoarytenoid muscles with action potentials that corresponded to spontaneous respiratory efforts, while the donor cricothyroid muscles retained their phasic contraction. These responses were obliterated when the recurrent laryngeal nerve conduit was divided. Histologic examination of the intrinsic laryngeal muscles demonstrated successful reinnervation. CONCLUSIONS: The results confirm that intrinsic laryngeal muscles may be successfully reinnervated by the superior laryngeal nerve with the muscle-nerve-muscle technique, without sacrifice of function of the cricothyroid muscle. This method offers an alternative source of appropriately firing axons for laryngeal reinnervation procedures.     

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.     

Difficulty producing high-pitched sounds in singing: correlations with laryngostroboscopy and electromyographic findings

IntroductionDifficulties or limitations in producing high-pitched sounds while singing may be due to the vocal technique used or organic factor. The observation of such difficulty or limitation by singing teachers is one of the main reasons affected individuals are referred to otolaryngologists.ObjectiveTo evaluate the laryngostroboscopic and electromyographic changes in the cricothyroid muscles of singers with difficulties or limitations producing high-pitched sounds.MethodsThis is a cross-sectional study. Ten singers with difficulty producing high-pitched sounds underwent voice, laryngostroboscopic, and electromyographic evaluations.ResultsNone of the evaluated singers presented signs of impairment of the superior laryngeal nerve on laryngostroboscopy. The electromyographic findings for the cricothyroid muscle were normal for all singers. Six singers presented vocal fold lesions, seven had signs suggestive of laryngopharyngeal reflux, and two presented vascular changes.ConclusionNo signs suggestive of superior laryngeal nerve paresis or paralysis were observed on laryngostroboscopy and electromyography of the cricothyroid muscle in singers with difficulties or limitations producing high-pitched sounds. The presence of vocal fold lesions should be investigated in this population.     

人喉返神经分支的应用解剖研究

目的：了解喉返神经在喉内的分支及分布,为施行选择性喉返神经吻合术提供解剖学依据。方法：５０例正常人新鲜喉标本进行系统的显微神经解剖研究。结果：９５％喉返神经在距同侧环甲关节下方１．０－２．５ｃｍ处形成喉返神经喉外分叉点,根据分支情况可将分为三型。喉内肌除环甲状外,均由喉返神经前支支配,其中８８％的环杓后肌为喉返神经前支发出单支支配;１２％为双支支配,结论：在甲状软骨板后下部处开窗,可显露同侧喉返神     

Synchrony of laryngeal muscle activity in persons with vocal tremor

OBJECTIVE: To determine if the tremor activity in laryngeal muscles is synchronous, which would indicate a single central source of tremor. DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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.     

Laryngeal Muscle Activity During Speech Breaks in Adductor Spasmodic Dysphonia

To determine the laryngeal muscle activation abnormalities that are associated with speech symptoms in adductor spasmodic dysphonia (ADSD), electromyographic measures of extrinsic and intrinsic laryngeal muscles during speech compared 1) muscle activity when ADSD patients had breaks in words with when they produced the same words without breaks; and 2) muscle activity in ADSD patients during speech without voice breaks with normal controls producing phonetically similar words. Simultaneous electromyographic recordings were made from the thyroarytenoid (TA), cricothyroid (CT), sternothyroid (ST), thyrohyoid(TH) and the posterior cricoarytenoid (PCA) muscles during speech testing in 11 ADSD patients and 10 control subjects. Speech breaks were identified and mean muscle activity measured starting 100 ms preceding a voice break and for the remainder of the word. Mean muscle activity level was significantly greater on break than non break words in ADSD patients only for the thyroarytenoid muscle(p<.001). No significant differences were found between the ADSD and control subjects during non break words for any of the laryngeal muscles studied. The results demonstrated that 1) only the thyroarytenoid, of the muscles tested, was affected in ADSD, 2) that muscle activation abnormalities were spasmodic, only appearing when symptoms occurred and 3) no imbalances of muscle tone were evident when speech disruptions did not appear.     

Rehabilitation of the crippled larynx: Application of the tucker technique for muscle-nerve reinnervation

Interruption of laryngeal innervation may partially or totally impair respiration, deglutition and phonation — the three basic laryngeal functions. Tucker has developed a principle of muscle-nerve pedicle transfer for laryngeal reinnervation to relieve airway obstruction following bilateral recurrent laryngeal nerve injury. We have applied the principle of reinnervation proposed by Tucker to treat patients not only with airway obstruction, but also with aspiration and impaired phonation due to interruption of laryngeal innervation. There were 23 patients in this study. The functional defects included: Voice alteration in 10 patients, airway obstruction in 8 and aspiration, as well as a voice change, in 5. The causes of injury were surgery in 9 patients, trauma in 5, tumor in 3, polio in 1 and a birth defect in 1 patient. No cause of nerve injury could be determined in 4 patients. The technique employed involved selective reinnervation of the laryngeal nerve branches to one or more laryngeal muscle groups; the muscle groups reinnervated were selected so as to overcome the functional defect of each particular patient. The patients have been followed for 6 mo. or longer. The results have been independently evaluated by a speech pathologist and documented by indirect and direct endoscopic observations, as well as by audio and audio-video recordings. In some cases, there was further documentation by cine-fluoro-audio tape recordings, laryngo-pharyngography, laryngeal tomography and pulmonary function studes. The muscle-pedicle transfer technique described by Tucker was found to be useful to correct laryngeal dysfunction in carefully selected cases.     

Physiologic motion after vocal cord reinnervation: A preliminary study

This study attempted to reestablish physiologic vocal cord motion, rather than synkinesis, to a rein-nervated vocal cord. One mongrel dog underwent a division and reanastomosis of the anterior branch of the right recurrent laryngeal nerve and simultaneous separation and reimplantation of a posterior division nerve-muscle pedicle into the posterior cricoarytenoid muscle. After 21 weeks, spontaneous physiologic vocal cord movement and electromyographic (EMG) activity were recorded during respiratory obstruction and laryngeal mechanical stimulation. Acoustic measures and histologic data are also presented from the reinnervated and normal vocalis muscle and from the recurrent laryngeal nerve. This study demonstrated that physiologic vocal cord motion can be achieved after laryngeal reinnervation using this technique.     

Laryngeal features of external superior laryngeal nerve denervation: revisiting a century-old controversy

A long-standing controversy exists regarding the laryngoscopic features associated with unilateral denervation of the external superior laryngeal nerve (ESLN). Recently, we modeled acute unilateral cricothyroid muscle paralysis by blocking the ipsilateral ESLN with lidocaine hydrochloride, and identified epiglottic petiole deviation to the side of paralysis during high-pitched voice production as a possible diagnostic sign. This study provides preliminary clinical evidence supporting the presence of petiole deviation in cases of ESLN denervation. Epiglottic petiole deviation to the side of weakness was present in electromyographically confirmed cases of unilateral partial or complete ESLN denervation, in isolation or in combination with denervation of other branches of the vagus nerve. In addition, a case of complete ESLN and recurrent laryngeal nerve (RLN) denervation showed return of the petiole to the midline 6 months after surgical reinnervation of the ESLN and RLN. Finally, petiole deviation was not present in isolated RLN paralysis--a finding suggesting that the diagnostic sign is uniquely associated with ESLN denervation. We concluded that deviation of the petiole to the side of cricothyroid muscle weakness during high-pitched voice production represents a potential diagnostic sign of unilateral ESLN denervation. Further research is necessary to determine factors that influence the expression and detection of this sign, as well as its diagnostic precision.     

Abductor laryngeal dystonia: a series treated with botulinum toxin.

Abductor laryngeal dystonia (LD) is characterized by a hoarse voice quality which is broken up by breathy or whispered portions. Botulinum toxin injection (Botox) has been a safe and effective treatment for adductor laryngeal dystonia and is currently accepted medical therapy. As an extension of the established treatment program, in 1989 treatment of abductor LD was initiated. Thirty-two patients have been treated by sequential percutaneous electromyogram-guided (EMG) injections of the posterior cricoarytenoid (PCA) muscles. Most patients required treatment of both PCA muscles and improved to an average of 70% of normal voice. Patients who had a preexisting tremor, evidence of dystonia in other muscle groups, vocal tremor, or respiratory dysrhythmia had less improvement. Ten patients also required injection of the cricothyroid muscles and/or type I laryngoplasty.     

Transcricothyroid, intraoperative monitoring of the vagus nerve

OBJECTIVE: To develop a reliable, user-friendly, intraoperative, electromyographic monitoring technique to decrease the incidence of injury to the recurrent and superior laryngeal nerves. DESIGN: Prospective, nonrandomized, clinical trial of a nerve monitoring technique. SETTING: Private tertiary care community hospital. PATIENTS: A population-based sample of 31 patients scheduled to undergo thyroid surgery was enrolled consecutively. Included in the study were patients older than 18 years who were scheduled for surgery and who were able to provide informed consent. Exclusion criteria were pregnancy, implanted metallic devices, and history of laryngeal surgery, injury, paresis, hoarseness, or paralysis. No patients were excluded, and all completed the study and returned for follow-up visits. INTERVENTIONS: Twenty-nine patients required total thyroidectomy, of which 10 involved malignancy, and the other 2 patients required lobectomy. Each patient completed the Voice Handicap Index and underwent a preoperative fiberoptic laryngeal examination. Continuous monitoring was performed using a widely available, commercial nerve integrity monitor and a paired electrode placed into the cricothyroid space under direct vision. Postoperatively, participants completed a follow-up Voice Handicap Index survey and underwent a laryngeal examination. MAIN OUTCOME MEASURES: The incidence of vocal paresis, or paralysis, and the preoperative and postoperative voice handicap score were recorded. The usefulness of the device based on the surgeon's subjective and immediate postoperative impressions was rated on a visual analog scale. RESULTS: Sixty-two recurrent laryngeal nerves were identified with continuous electromyographic monitoring. Vocal cord paresis or paralysis was not observed. Postoperative Voice Handicap Index scores were unchanged from preoperative assessment. The technique was given a rating of 1 (most useful) on a 5-point scale in 70% of cases. CONCLUSIONS: The technique described is sensitive, easy to use, accurate, and associated with a high degree of surgeon satisfaction. This technique is not associated with additional risk to the patient and offers the potential to reduce injury. Monitoring provides assurance that the nerve is intact and functioning prior to extubation.     

Spontaneous laryngeal reinnervation after recurrent laryngeal or vagus nerve injury

OBJECTIVES: The status of innervation in patients with laryngeal paralysis is somewhat controversial. Electromyographic activity has been frequently documented in the laryngeal muscles of patients with laryngeal paralysis, and animal experiments report a strong propensity for reinnervation after laryngeal nerve injury. However, a study of intraoperative electromyography performed in patients during reinnervation surgery failed to document activity with stimulation of the recurrent laryngeal nerve (RLN). Noting the long-observed differences in the symptoms of patients with vagus nerve injury and those with RLN injury, I hypothesized that reinnervation is influenced by the site of nerve injury. METHODS: Cats were sacrificed at various intervals after resection of 1 cm of either the RLN or the vagus nerve, without any attempt to repair the nerve. RESULTS: Four months after RLN resection, distal nerve biopsy revealed unmyelinated axons scattered through fibrous tissue. By 6 months, myelinated axons were organized, and electromyographic and histologic examination showed preferential reinnervation of the thyroarytenoid muscle. After vagotomy, the RLN was fibrotic and no axons were present. Both the thyroarytenoid and posterior cricoarytenoid muscles were fibrotic and had no electromyographic activity. CONCLUSIONS: The results confirm the strong propensity for laryngeal reinnervation after RLN injury, but not after vagus nerve injury. Preferential reinnervation of adductor muscles may account for a medial position of the paralyzed vocal fold.     

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.     

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.     

膈神经替代喉返神经修复治疗双侧声带麻痹

目的 探讨膈神经喉返神经吻合和内收肌支环杓后肌植入术（膈神经手术）治疗双侧喉返神经损伤声带麻痹的有效性、可行性。方法 第二军医大学长海医院耳鼻咽喉科1999年8月－2001年7月治疗外伤性双侧喉返神经损伤声带麻痹6例。病程1周－18个月，一侧作膈神经手术，而另一侧作颈袢肌蒂环杓后肌植入术。手术前后电子喉镜、频闪喉镜观察声门大小、声珲运动、振动情况，噪音声学参数分析，喉肌电力产检查评价手术效果。结果 术后2－3周检查发现4例声门较术前增大2－3mm，但声带固定不动，2例无明显改善。术后6个月5例膈神经修复侧均恢复了较大幅度的吸气性声带外展功能，外展幅度可达3－5mm，而肌蒂植入侧仅轻微外展或固定不动，幅度均在1mm以内。此5例均顺利拔管，并能承受较大强度的体力活动，1例仍在随访中。术后4个月6例肌电图检查显示膈神经修复侧自发、诱发电位均明显大于肌蒂植入侧，自发电活动与肋间肌基本同步，而较肌蒂植入侧延迟100－200ms。声音估价显示3例声嘶术后较术前好转，2例无变化。术后半年肺功能均恢复正常。结论 膈神经喉返神经吻合内收肌支环杓后肌植入术安全可行，较颈袢肌蒂植入术更能有效地恢复声带吸气性外展运动，值得临床推广应用。     

Combined arytenoid adduction and laryngeal reinnervation in the treatment of vocal fold paralysis

OBJECTIVE/HYPOTHESIS: Glottal closure and symmetrical thyroarytenoid stiffness are two important functional characteristics of normal phonatory posture. In the treatment of unilateral vocal cord paralysis, vocal fold medialization improves closure, facilitating entrainment of both vocal folds for improved phonation, and reinnervation is purported to maintain vocal fold bulk and stiffness. A combination of medialization and reinnervation would be expected to further improve vocal quality over medialization alone. STUDY DESIGN: A retrospective review of preoperative and postoperative voice analysis on all patients who underwent arytenoid adduction alone (adduction group) or combined arytenoid adduction and ansa cervicalis to recurrent laryngeal nerve anastomosis (combined group) between 1989 and 1995 for the treatment of unilateral vocal cord paralysis. Patients without postoperative voice analysis were invited back for its completion. A perceptual analysis was designed and completed. METHODS: Videostroboscopic measures of glottal closure, mucosal wave, and symmetry were rated. Aerodynamic parameters of laryngeal airflow and subglottic pressure were measured. A 2-second segment of sustained vowel was used for perceptual analysis by means of a panel of voice professionals and a rating system. Statistical calculations were performed at a significance level of P = .05. RESULTS: There were 9 patients in the adduction group and 10 patients in the combined group. Closure and mucosal wave improved significantly in both groups. Airflow decreased in both groups, but the decrease reached statistical significance only in the adduction group. Subglottic pressure remained unchanged in both groups. Both groups had significant perceptual improvement of voice quality. In all tested parameters the extent of improvement was similar in both groups. CONCLUSION: The role of laryngeal reinnervation in the treatment of unilateral vocal cord paralysis remains to be established.     

Selective denervation: reinnervation for the control of adductor spasmodic dysphonia

OBJECTIVES: The objective of this study was to evaluate the efficacy of a new surgical procedure for adductor spasmodic dysphonia (AddSD). This surgery involves the bilateral selective division of the adductor branches of the recurrent laryngeal nerves with immediate reinnervation of the distal nerve trunks with branches of the ansa cervicalis (selective denervation-reinnervation). METHODS: Our first six patients to undergo this procedure were enrolled in the study. All patients suffered from AddSD and had previously received botulinum toxin A (Botox, Allergen, Markham, ON) therapy. Patients were recorded preoperatively and all underwent the same surgical procedure performed by the same lead surgeon. All patients were surveyed postoperatively and then re-recorded. Expert and untrained judges undertook perceptual evaluation of voice quality. Voice samples were also objectively evaluated for aphonic voice breaks. RESULTS: No major surgical complications were noted. Patient satisfaction was excellent, and five of the six patients no longer require botulinum toxin therapy. In five of the six patients, the majority of untrained and expert listeners perceived the postoperative voice to be superior. Objectively, the rate of aphonic voice breaks was also reduced in five of the six patients.     

Laryngeal electromyography in adults with Parkinson's disease and voice complaints

OBJECTIVE: To study the laryngeal electromyography (LEMG) pattern in patients with Parkinson's disease (PD) and vocal complaints. STUDY DESIGN AND SETTING: Twenty-six adults with PD and vocal complaints and 26 controls with presbyphonia underwent videolaryngoscopy (VL) and LEMG. RESULTS: No tremor was found on LEMG of the cricothyroid and thyroarytenoid muscles, even in cases with clinical and VL tremor. LEMG hypertonicity during voice rest was the typical feature observed in 73% of the patients with PD versus 23% of the controls. This difference was statistically significant. The severity of the disease, diagnosis, and the time of treatment did not correlate with LEMG findings. CONCLUSION: This is the first study reporting the use of LEMG in a large series of patients with PD and vocal complaints. Patients with PD presented spontaneous intrinsic laryngeal muscle activity during voice rest. SIGNIFICANCE: The typical patterns in LEMG suggest this to be a valuable diagnostic tool in PD.     

Useful landmarks in arytenoid adduction and laryngeal reinnervation surgery

OBJECTIVE: Knowledge of the location of the muscular process of the arytenoid cartilage and the recurrent laryngeal nerve is essential to performing a successful arytenoid adduction and laryngeal reinnervation surgery. We describe external landmarks useful in locating these structures. STUDY DESIGN: Cadaveric laryngeal dissection. METHODS: Posterior laryngeal dissection was performed in 16 human larynges. The position of the muscular process of the arytenoid was measured bilaterally relative to the inferior and superior borders of the thyroid lamina. The recurrent laryngeal nerve was followed distally from slightly below the level of the cricothyroid joint to its genu where its vertical course changes to an oblique intralaryngeal course. RESULTS: The muscular process of the arytenoid was usually found halfway between the roots of the superior and inferior cornu of the thyroid lamina. The recurrent laryngeal nerve was found just deep to the cricothyroid joint and lateral to the posterior cricoarytenoid muscle. There were no other nerves in this area. CONCLUSIONS: This study finds that the superior and inferior borders of the thyroid lamina are useful intraoperative landmarks to locate the muscular process of the arytenoid. The cricothyroid joint provides a good starting point to locate the recurrent laryngeal nerve, which can be identified slightly deeper between it and the posterior cricoarytenoid muscle.     

Laryngeal reinnervation

Laryngeal reinnervation refers to any of a number of surgical procedures intended to restore neural connections to the larynx, which have usually been lost from some type of trauma (eg, surgical).The nerve function(s) to be restored may be those of the recurrent laryngeal nerve or its subdivisions, those of the superior laryngeal nerve, or both, and they may be motor or sensory. Several different donor nerves are available and have been described. The technique used may be direct end-to-end anastomosis (neurorrhaphy), direct implantation of a nerve ending into a muscle, the nerve-muscle pedicle technique, or muscle-nerve-muscle methods. These nerves and techniques may be combined in many ways. A number of new techniques have been reported in animal studies; however, the animal studies do not always predict the results of analogous surgeries in human patients. The historical and current perspectives on these techniques are discussed in this article.