Experimental study on reinnervation of vocal cord adductors with the ansa cervicalis

Comparison of vocal outcome following two different procedures for immediate RLN reconstruction

The objective of this study was to compare time-dependent improvements in phonatory function and stroboscopic findings following two different procedures for immediate reconstruction of the recurrent laryngeal nerve (RLN) during neck tumor extirpation. Seventeen patients with neck tumors, consisting of advanced thyroid cancer (n = 15), metastatic neck lymph nodes from other malignant lesions (n = 2), underwent resection of the primary lesion and involved RLN. Immediate RLN reconstruction by either: (1) ansa cervicalis nerve (ACN) to RLN anastomosis (n = 8); or (2) placement of the great auricular nerve (GAN) between the cut ends of the RLN (n = 9) was performed from 2000 to 2011. Phonatory function [maximum phonation time, mean airflow rate (MFR), jitter, and shimmer) and stroboscopic findings (regularity, amplitude, and glottal gap) were examined at 1, 6, and 12 months postoperatively. Stroboscopic findings were assessed by two otolaryngologists and one speech pathologist. There were no significant differences in any parameter for either phonatory function or stroboscopic findings between ACN and GAN with the exception of jitter and shimmer, in which ACN was superior to GAN at 1 month postoperatively. All parameters improved significantly between 1 and 12 months postoperatively for both phonatory function and stroboscopic findings (P < 0.05). Either method of immediate RLN reconstruction at the time of neck tumor extirpation (i.e., ACN or GAN) provided both excellent long-term postoperative phonatory function and stroboscopic findings, and there was little difference in vocal outcome between the two procedures.

Changes in electrical response function and myosin heavy chain isoforms following denervation and reinnervation of bilateral posterior cricoarytenoid muscles in dogs

CONCLUSIONS

Both electrical response function and mRNA expression of myosin heavy chain (MyHC) types 2X, 1, and Neonatal of bilateral posterior cricoarytenoid (PCA) muscle changed after denervation or reinnervation in canines.

OBJECTIVES

There is a need to investigate the electrical response function MyHC alteration of denervation or reinnervation in the bilateral PCA muscle of large animals.

METHODS

MyHC isoforms expression profile and PCA muscle function outcome were detected by real-time reverse transcribed-polymerase chain reaction and muscle response to functional electrical stimulation, 9 weeks after denervation and reinnervation with ansa-recurrent laryngeal nerve anastomosis in dogs.

RESULTS

Denervation produced up-regulation of MyHC-1 and MyHC-Neonatal messenger ribonucleic acid (mRNA) expression. Reinnervation caused a decrease of MyHC-2X mRNA expression. The electrical voltage threshold of vocal fold movement and maximum abduction of denervation were greater than that of the reinnervated or control group. The denervated vocal abduction maximum of response to electrical stimulation was less than that in reinnervation or control groups.

Laryngeal reinnervation using ansa cervicalis for thyroid surgery-related unilateral vocal fold paralysis: a long-term outcome analysis of 237 cases

Objective

To evaluate the long-term efficacy of delayed laryngeal reinnervation using the main branch of the ansa cervicalis in treatment of unilateral vocal fold paralysis (UVFP) caused by thyroid surgery.

Summary of Background Data

UVFP remains a serious complication of thyroid surgery. Up to now, a completely satisfactory surgical treatment of UVFP has been elusive.

Methods

From Jan. 1996 to Jan. 2008, a total of 237 UVFP patients who underwent ansa cervicalis main branch-to-recurrent laryngeal nerve (RLN) anastomosis were enrolled as UVFP group; another 237 age- and gender-matched normal subjects served as control group. Videostroboscopy, vocal function assessment (acoustic analysis, perceptual evaluation and maximum phonation time), and electromyography were performed preoperatively and postoperatively. The mean follow-up period was 5.2±2.7 years, ranging from 2 to 12 years.

Results

Analysis of videostroboscopic findings indicated that the glottic closure, vocal fold edge, vocal fold position, phase symmetry and regularity were significantly improved in the UVFP group (P<0.001, postoperative vs. preoperative). The postoperative parameters of vocal function were also significantly improved in the UVFP group (P<0.001) and showed no statistical differences compared to the control group (P>0.05, respectively). Postoperative laryngeal electromyography confirmed successful reinnervation of laryngeal muscle.

Conclusions

Delayed laryngeal reinnervation with the main branch of ansa cervicalis is a feasible and effective approach for treatment of thyroid surgery-related UVFP; it can restore the physiological laryngeal phonatory function to the normal or a nearly normal voice quality.

Modified arytenoid adduction for cancer-related unilateral vocal fold paralysis

OBJECTIVES

(1) To evaluate the efficacy of modified arytenoid adduction in the management of patients with symptomatic cancer-related unilateral vocal fold paralysis, and (2) to assess the impact of this treatment on patients' quality of life.

METHODS

Forty-two patients with cancer-related unilateral vocal fold paralysis underwent modified arytenoid adduction between February 2001 and December 2008. Of these, 37 patients were enrolled in this retrospective study (one patient died of primary disease and four were lost to follow up). Laryngostroboscopy was performed to evaluate vocal fold orientation and mobility. Pre- and post-operative assessment of subjective and objective voice, aerodynamic parameters, and quality of life were also undertaken, and aspiration was subjectively rated.

RESULTS

Laryngostroboscopic findings indicated a significant post-operative improvement in vocal fold posterior glottal closure and vertical gap. Significant improvements in voice quality, aerodynamic parameters and quality of life were noted three months post-operatively in all patients (p < 0.01). The overall success rate for swallowing rehabilitation was 94.6 per cent (35/37). Subjective aspiration ratings decreased significantly post-operatively, compared with pre-operative values (p < 0.01). No major complication occurred in any patient, except for dyspnoea in one patient.

CONCLUSION

Modified arytenoid adduction is an effective and reliable medialisation technique which can restore satisfactory voice quality, prevent aspiration and lead to a better quality of life for patients with cancer-related unilateral vocal fold paralysis.

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.

Immediate Recurrent Laryngeal Nerve Reconstruction and Vocal Outcome

OBJECTIVE

The objective of this prospective study was to assess the long-term effects of immediate reconstruction of the recurrent laryngeal nerve (RLN) during thyroid cancer extirpation on postoperative phonatory function.

SUBJECTS AND METHODS

The subjects were 22 patients with advanced thyroid cancer who underwent resection of the primary lesion and involved RLN. RLN paralysis was seen in 12 patients preoperatively and involvement of the RLN was noted intraoperatively in 10. Immediate reconstruction of the RLN was performed on eight patients using the great auricular nerve and one underwent direct anastomosis of the RLN stumps (group I). Nine patients opted not to have phonosurgical procedures (group II). The remaining four had arytenoid adduction immediately after cancer extirpation (group III). Phonatory function (stroboscopy, maximum phonation time [MPT], mean airflow rate [MFR], harmonics-to-noise ratio [HNR], jitter, and shimmer) was followed for at least 9 months.

RESULTS

Minimal or no glottal gap during phonation was observed in six patients in group I, whereas the patients in group II had a large gap along the entire fold. HNR, MPT, and MFR were significantly better in group I (17.7 +/- 3.6 dB, 15.1 +/- 6.3 s, and 100 +/- 32 mL/s, respectively) than in group II (12.1 +/- 2.9 dB, 5.4 +/- 3.1 s, and 430 +/- 207 mL/s, respectively). Patients in group III had a gap of varying degrees along the membranous fold. Although HNR, shimmer, and MPT in group III were comparable to group I, the other parameters were less favorable than in group I.

CONCLUSION

Immediate RLN reconstruction at the time of thyroid cancer extirpation can provide excellent postoperative phonatory function.

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.

Neurophysiology of vocal fold paralysis

Although a tremendous volume of energy and literature has been devoted to laryngeal paralysis in the past decade, there are still substantial gaps in our understanding of fundamental issues. Oddly enough, controversy remains regarding the actual innervation pathways of the larynx and whether the paralyzed larynx is truly denervated or dysfunctionally reinnervated. An appreciation of these basic issues is prerequisite to making prudent decisions regarding the most appropriate type of intervention. The purpose of this article is to provide a brief overview of basic laryngeal anatomy and neurophysiology to prepare the reader for a subsequent discussion of futuristic research for treatment of laryngeal paralysis.A novel approach is described, which can induce selective reinnervation of individual laryngeal muscles by their original motor fibers within the recurrent laryngeal nerve.

Electromyographic findings in recurrent laryngeal nerve reinnervation

Abductor, adductor, and combined reinnervation procedures have been explored with variable success rates. We describe the experience of a tertiary care center with adductor reinnervation procedures, including preoperative and postoperative videostroboscopy and electromyography (EMG) findings. A retrospective chart review was performed from 1997 to 2001 that included 9 patients. Preoperative and postoperative voice comparison was performed by 3 blinded speech pathologists. Clinical comparisons of videostroboscopy findings for vocal fold bulk, tone, position, presence of gap, and movement are elucidated. The preoperative and postoperative EMG findings are described. In all patients, preoperative EMG revealed a dense, complete denervation of the affected recurrent laryngeal nerve. No movement was noted on videostroboscopy with persistent glottic gap. Reinnervation involved a nerve-muscle pedicle or a direct neurorrhaphy of the ansa cervicalis to the recurrent laryngeal nerve. Voice improvement was noted between 60 days and 3 months after reinnervation. Four postoperative EMG studies were performed. An early postoperative EMG study at 5 months revealed activation of the lateral cricoarytenoid muscle and thyroarytenoid muscle with head-lift. Videostroboscopy showed excellent near-midline static positioning of the vocal fold. Late EMG studies, performed 12 to 16 months after reinnervation, revealed "learning" of these muscles, with new activation on "eee" phonation. We conclude that recurrent laryngeal nerve reinnervation procedures belong in the armamentarium of the laryngologist for the treatment of vocal fold paralysis. The EMG findings reported in this study suggest that ongoing reinnervation allows for activation with phonation in matured neuronal anastomoses. Overall, this procedure results in excellent patient acceptance and near-normal vocal quality.

Laryngeal reinnervation with the hypoglossal nerve: II. Clinical evaluation and early patient experience

OBJECTIVES/HYPOTHESIS

To determine whether the hypoglossal nerve (XII) can serve as a suitable donor for human laryngeal reinnervation.

STUDY DESIGN

Prospective, nonrandomized.

METHODS

Measurements were made on patients undergoing open neck procedures to determine the length of XII available and that required to perform XII-recurrent laryngeal nerve (RLN) anastomosis. The morbidity of combined XII and RLN injuries was studied using temporary lidocaine block of the ipsilateral XII in patients with unilateral vocal fold paralysis (UVFP). A pilot series of patients with UVFP who underwent XII-RLN reinnervation was evaluated for morbidity of the procedure, and for improvement in voice and swallowing.

RESULTS

In 89 necks the average available length of XII was 2 cm less than that needed to reach the larynx, indicating the RLN stump must be at least 3 cm to allow tension-free anastomosis. Twenty-five patients with untreated UVFP underwent temporary lidocaine block of XII; 8 had slight changes in their speech, none had increased aspiration. Nine patients underwent XII-RLN reinnervation. Postoperative speech analysis correlated well with the findings of the temporary lidocaine block of XII. One-year follow-up of five patients showed excellent voice quality, resolution of any preoperative aspiration, and minimal morbidity. Slight adductory movement of the reinnervated vocal fold was seen during tongue thrust. Electromyography confirmed substantial polyphasic action potentials in the thyroarytenoid muscle.

CONCLUSIONS

The hypoglossal nerve is a very suitable donor for reinnervation of patients with UVFP. There should be enough length for primary XII-RLN anastomosis in most patients. Donor site morbidity is acceptable. Preoperative lidocaine block of XII is a good predictor of actual donor site morbidity and could be used to assess patients undergoing facial-hypoglossal anastomosis as well.

An experimental comparison of different kinds of laryngeal muscle reinnervation

In this study, we attempted to determine which method was the best for reinnervating the laryngeal adductor muscles by comparing nerve suture, nerve implantation, and nerve-muscular pedicle (NMP) transfer, as well as the length of time that could elapse after denervation and still allow for successful reinnervation with the ansa cervicalis. Reinnervation was performed in 36 dogs, at 6-, 8-, 10-, 12- and 18-month intervals after denervation via the three methods of muscle reinnervation described above. We noted some return of adduction in the cases using nerve suture before a 10-month interval after denervation, and with nerve implantation and NMP transfer before the 8-month intervals. The variable adduction was caused by reinnervation of the adductor muscles from the ansa cervicalis, as demonstrated by laryngeal spontaneous and evoked electromyography, the strength of muscle contraction, and histologic findings. Adduction was not observed in the cases after the above-mentioned intervals but partial improvement of the bulk and strength of the reinnervated vocal cord was still achieved. An analysis of the experimental results showed that nerve suture was superior to nerve implantation and the NMP technique. Little difference was noted between nerve implantation and the NMP technique.

Update: laryngeal reinnervation for unilateral vocal cord paralysis with the ansa cervicalis

Eight patients underwent ansa cervicalis anastomosis to the adductor branch of the recurrent laryngeal nerve for unilateral vocal cord paralysis. They were followed long enough (at least 1 year) to determine if the procedure was successful. All cases have been subjected to preoperative and postoperative voice recording, acoustic analysis, and videolaryngoscopy. Some of them have been subjected to stroboscopy and electromyography (EMG). Data from these cases indicate that satisfactory phonatory quality may be achieved after the procedure. The reinnervated vocal cord neither abducted nor adducted, but it presented itself in midline for precise apposition with the normal cord. Synchronous mucosal waves in both vocal cords could be observed. EMG showed that the procedure produced satisfactory reinnervation of the adductory muscles. Therefore, the authors believe that the procedure could be proposed as an alternative to Teflon injection or thyroplasty in selected cases.