Laryngeal transplantation in 2005: a review.

There is no good surgical, medical or prosthetic solution to the problems faced by those with a larynx whose function is irreversibly damaged by tumor or trauma. Over the past 10 years, the pace of research designed to establish laryngeal transplantation as a therapeutic option for these persons has increased steadily. The biggest milestone in this field was the world's first true laryngeal transplant performed in Cleveland, Ohio in 1998. The recipient's graft continues to function well, in many respects, even after 7 years. However, it has also highlighted the remaining barriers to full-scale clinical trials. Stimulated by these observations, several groups have accumulated data which point to answers to some of the outstanding questions surrounding functional reinnervation and immunomodulation. This review seeks to outline the progress achieved in this field by 2005 and to point the way forward for laryngeal transplantation research in the 21st century.

Lack of evoked laryngeal electromyography response in patients with a clinical diagnosis of vocal cord paralysis.

There has been recent debate about whether patients with vocal cord immobility have a neurologic paralysis or whether synkinesis, the misdirection of axons to competing laryngeal muscles, is responsible for the lack of voluntary vocal cord motion. This issue was studied in 15 patients with vocal cord paralysis who underwent laryngeal reinnervation. Evoked electromyography was performed with a surface electrode endotracheal tube. The recurrent laryngeal nerve (RLN) was identified and stimulated with constant current. Of the 15 patients, only 1 produced a compound muscle action potential upon nerve stimulation. The remaining 14 patients had no evoked response during RLN stimulation. A control group of 8 patients with normal vocal cord mobility was studied, and each had a normal evoked electromyography response after RLN stimulation. These results support the assertion that patients who require treatment for vocal cord paralysis do not have synkinesis produced by RLN reinnervation.

Clicking in the throat: cinematic fiction or surgical fact?

The complaint of a clicking in the throat when swallowing is uncommon but very discomforting and painful for those who experience it. It is such an unusual complaint that symptoms may be dismissed as psychogenic because a cause for the problem may not be readily apparent. We present a series of 11 cases in which all patients had an audible clicking or popping noise in the throat associated with neck and throat pain when swallowing or turning the neck. The most helpful diagnostic procedure was careful examination and palpation of the neck while the patient swallowed to localize the side and source of the clicking. Laryngeal computed tomographic (CT) scans helped in some cases to demonstrate thyroid-cartilage and/or vertebral body asymmetry. Each case was treated with surgery of the neck and larynx to trim the portion of the thyroid cartilage causing the clicking. In most cases the superior cornu of the thyroid cartilage projected posteriorly and medially. Surgery was successful in all cases to eliminate the symptoms. Though an uncommon complaint, our experience suggests that the clicking throat is a surgically treatable problem.

Combined buccal mucosa island and sternohyoid flaps: a new technique of hemilaryngeal reconstruction studied in a canine model.

No single method of reconstruction has proven ideal for all patients with defects following vertical hemilaryngectomy. In this report, we detail a new technique for hemilaryngeal reconstruction involving the use of a pedicled buccal mucosa island flap supplied by the facial artery and vein. The buccal flap was used to resurface a transversely oriented sternohyoid myofascial flap. The reconstructive outcome was analyzed in 4 animals, 3 of which survived the early postoperative period. Videoendoscopy and stroboscopy were performed to analyze the laryngeal configuration and vibration. Each subject was decannulated and had a competent airway free of aspiration. After sacrifice of the animals, whole organ axial sections were made at multiple levels. Endoscopic and histologic findings documented that this technique produced an appropriate neocord position. Laryngeal stroboscopy in each animal showed bilateral mucosal traveling waves, with entrainment of the reconstructed neocord mucosa and native vocal cord mucosa. We conclude that the layered reconstructive technique described, compared to traditional methods of reconstruction, more closely replicates the structure of the excised tissue in hemilaryngeal reconstruction, potentially resulting in an improved voice outcome.

Radial forearm free flap pharyngoesophageal reconstruction.

OBJECTIVES: This study evaluates the outcome of pharyngoesophageal reconstruction using radial forearm free flaps with regard to primary wound healing, speech, and swallowing in patients requiring laryngopharyngectomy. STUDY DESIGN: Retrospective review in the setting of a tertiary, referral, and academic center. PATIENTS AND METHODS: Twenty patients underwent reconstruction of the pharyngoesophageal segment using fasciocutaneous radial forearm free flaps. RESULTS: All free flap transfers were successful. An oral diet was resumed in 85% of the patients after surgery. Postoperative pharyngocutaneous fistulas occurred in 4 patients (20%) with 3 resolving spontaneously. Distal strictures also occurred in 20% of the patients. Five patients who underwent tracheoesophageal puncture achieved useful speech. CONCLUSIONS: Advantages of radial forearm free flaps for microvascular pharyngoesophageal function include high flap reliability, limited donor site morbidity, larger vascular pedicle caliber, and the ability to achieve good quality tracheoesophageal speech. The swallowing outcome is similar to that achieved after jejunal flap pharyngoesophageal reconstruction. The main disadvantage of this technique relates to a moderately high incidence of pharyngocutaneous fistulas, which contributes to delayed oral intake in affected patients.

Hemilaryngeal transplantation in the canine model: technique and implications.

PURPOSE: There is no ideal method for reconstruction of hemilaryngeal defects because there is no autologous flap or graft that can reproduce the unique structural properties of the larynx. In this article, the technique, potential research, and clinical applications of hemilaryngeal transplantation are addressed. MATERIALS AND METHODS: In a canine model, transplantation of a hemilarynx was performed. The thyroarytenoid muscle was reinnervated, and an arytenoid adduction was performed to ensure a competent larynx during the early postoperative period. RESULTS: The canine tolerated the procedure well and the transplanted larynx remained healthy and well vascularized during the postoperative period. Electromyography of the transplanted thyroarytenoid muscle verified reinnervation 2 months after the procedure. During induced phonation, vibration was symmetrical with a normal-appearing laryngeal geometry. CONCLUSIONS: Preliminary experience indicates that this technique has unique advantages compared with other available techniques for laryngeal reconstruction. Only with additional progress in transplantation medicine could this procedure be considered an option for reconstruction of human partial laryngeal defects.

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.

Recovery of laryngeal sensation after superior laryngeal nerve anastomosis.

OBJECTIVES/HYPOTHESIS: Reliable motor reinnervation has been show in multiple laryngeal transplant studies; however, sensory reinnervation of the larynx after nerve anastomosis has yet to be demonstrated. The role of sensory nerve anastomosis in the transplanted larynx in unknown, but is thought to be necessary to provide airway protection. A canine model was developed to examine the possibility of reformation of sensory pathways in the larynx after nerve section and anastomosis. STUDY DESIGN: Randomized controlled experiment. METHODS: Ten canines were randomly assigned to two groups. Hydrochloric acid-induced laryngospasm was demonstrated in every dog. All dogs then had their necks explored, and the internal branch of the superior laryngeal nerve was identified and transected bilaterally. Following nerve section all dogs were retested for an acid-induced laryngospasm reflex. The control group had their wounds closed and were then awakened from anesthesia. The study group underwent microscopic anastomosis of their sensory nerves. Following a 6-month period the two groups of dogs were compared for the presence of the laryngospasm reflex. RESULTS: No dog in the control group had a response to the acid. All dogs in the study group had some response to the acid, although none of them had return of true laryngospasm. CONCLUSION: We concluded that sensory reinnervation does occur after nerve anastomosis, but the recovery of sensation may be incomplete or altered.

Role of motor unit number estimate electromyography in experimental canine laryngeal reinnervation.

Laryngeal electromyography has been used clinically to differentiate neuromuscular pathology from other causes of vocal fold immobility such as arytenoid dislocation, tumor invasion, or cricoarytenoid joint fixation. Electromyography has also been used to predict the prognosis for nerve recovery in laryngeal paralysis. Existing electromyographic techniques either record activity with voluntary motion or study nerve conduction. In this study a new technique, motor unit number estimation, a commercially available quantitative method of electromyographic analysis, is used to study the progress of recovery of vocal fold function after recurrent laryngeal nerve injury. Four dogs underwent transection and immediate reanastomosis of selected branches of the adductor and abductor branches of the recurrent laryngeal nerve on 1 side; the opposite side served as a control. Baseline electromyographic and videolaryngoscopic studies were performed. These measures were then repeated in a longitudinal fashion every 6 weeks after denervation. The motor unit number estimation technique indicated a return of motor unit numbers with time, along with estimates of their size. This was consistent with the expected progress of laryngeal reinnervation. These data and their predictive value for nerve recovery will be discussed.

Treatment of Parkinson hypophonia with percutaneous collagen augmentation.

OBJECTIVES: It has been estimated that more than 70% of patients with Parkinson disease experience voice and speech disorders characterized by weak and breathy phonation, and dysarthria. This study reports on the efficacy of treating Parkinson patients who have glottal insufficiency. STUDY DESIGN AND METHODS: Thirty-five patients underwent collagen augmentation of the vocal folds for hypophonia associated with Parkinson disease, using a new technique of percutaneous injection with fiberoptic guidance. Patient response to the collagen augmentation was determined by telephone survey. RESULTS AND CONCLUSIONS: The procedure required minimal patient participation and was safely performed on all the patients who were studied. Results of the survey indicated that 75% of patient responses demonstrated satisfaction with the technique, compared with 16% of patient ratings reflecting dissatisfaction. These results were moderately correlated with the duration of improvement of the dysphonia. Results of this preliminary evaluation demonstrate that voice deficits in Parkinson disease are amenable to vocal fold augmentation. Because this procedure requires minimal patient participation and can be safely performed in an office setting, it may also be useful in other severely debilitating neuromotor diseases that result in glottal insufficiency and hypophonia.

Comparison of nerve banking techniques in delayed laryngeal reinnervation.

Successful laryngeal transplantation will require adequate reinnervation of the larynx to allow phonation, coordinated swallowing, and respiration. A delay between laryngectomy and transplantation would be necessary in oncology patients because of the need for immunosuppression. In these patients, reinnervation of the donor organ would require "banking" and recovery of dormant recipient recurrent laryngeal nerves (RLNs). This pilot study was undertaken to compare the effectiveness of RLN storage using 1 of 2 techniques: 1) inserting the nerve into a muscle pocket or 2) anastomosing the proximal RLN stump to the ansa cervicalis. Six months following nerve transection and "banking," the proximal anterior branch of the RLN was reanastomosed to the distal anterior segment and the posterior branch was anastomosed directly to the posterior cricoarytenoid muscle. Tensionometry, image analysis, and electromyographic data were collected 1 year later. Results show reinnervation of adductors and abductors with both techniques. Banking of the RLN branches during total laryngectomy is effective and should permit delayed physiological reinnervation following laryngeal transplantation.

Exit jet particle velocity in the in vivo canine laryngeal model with variable nerve stimulation.

This study extends previous work on exit jet particle velocity in the in vivo canine model of phonation by measuring air particle velocity at multiple locations in the midline of the glottis and across multiple levels of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) stimulation. In a second experiment, exit jet particle velocity was measured at midline and offmidline positions with constant levels of RLN and SLN stimulation. In this study, peak particle velocity was higher at the anterior commissure than at the posterior commissure in the midline of the glottis, and peak particle velocity was higher at the midline than at offmidline positions. In addition, increasing levels of RLN stimulation resulted in increasing peak particle velocity; however, increasing levels of SLN stimulation failed to produce a uniform effect on peak particle velocity.

Selective laryngeal adductor denervation-reinnervation: a new surgical treatment for adductor spasmodic dysphonia.

During the past decade, botulinum toxin (Botox) has emerged as the accepted treatment for adductor spasmodic dysphonia (ASD). This therapy, which produces bilateral weakness of the thyroarytenoid muscle, undoubtedly produces physiologic effects that are beneficial to patients with ASD. However, it also has important limitations, including the need for repeated injections, the unpredictable relationship between dosage and response, and the possibility of short-term swallowing and voice problems. In this study, we will report our preliminary experience with a new surgical treatment for ASD. In this new procedure, the adductor branch of the recurrent laryngeal nerve is selectively denervated bilaterally, and its distal nerve stumps are reinnervated with branches of the ansa cervicalis nerve. Each of the patients was followed for at least 12 months; the median follow-up is 36 months. The outcome of the operation in 21 consecutive patients is reported. Nineteen of the 21 patients were judged to have an overall severity of dysphonia that was "absent to mild" following the procedure. Only 1 patient underwent further treatment with Botox postoperatively. The implications of this new procedure for ASD are discussed.

Functional differences between the two bellies of the cricothyroid muscle.

The contraction of the cricothyroid (CT) muscle, which results in a decrease in the distance between the thyroid and cricoid cartilages, is considered to be the main factor in lengthening the vocal folds. This is achieved by rotation of the CT joint. The CT muscle is composed of two distinct bellies, the pars recta and the pars obliqua. The function of each subunit is not clearly understood, although it is believed that they act differently because their fibers run in different directions. To clarify the function of the two bellies in phonation, the fundamental frequency (F0), vocal intensity, subglottic pressure, vocal fold length, and CT distance were measured using an in vivo canine laryngeal model. On the basis of these measurements, we demonstrated that the two bellies are varied in their effect on raising the pitch, rotation, and forward translation of the CT joint. The stimulation of the pars recta nerve resulted in a greater increase in the F0 value compared with that of pars obliqua. The combined activity of the pars recta and pars obliqua is important in adjustment of the vocal fold length. The CT approximations directed parallel to the pars recta and pars obliqua simultaneously were more effective in elevation of the pitch than the approximation placed parallel to the pars recta only. This finding may be clinically significant with regard to CT approximation thyroplasty in human trails.

Extended canine laryngeal preservation for transplantation.

The goal of successfully transplanting the larynx has motivated researchers since the 1960s. Early laryngeal transplant techniques limited the donor larynx to 45 minutes of ischemia. In this study, a method of prolonged laryngeal preservation is employed in three canines. In vivo cold laryngeal perfusion with University of Wisconsin Solution (UWS) was performed. The larynx was removed and placed into cold storage in 4 degrees C UWS. After 24 hours of storage, the same canines underwent laryngeal reimplantation. The animals were sacrificed 7 days after reimplantation. No evidence of necrosis or vascular insufficiency was identified histologically. The results indicate that canine larynges can be successfully reimplanted after 24 hours of preservation. Future studies will assess the application of this technique to laryngeal transplantation.

Ansa cervicalis nerve: review of the topographic anatomy and morphology.

In recent years, there has been a proliferation of techniques utilizing the ansa cervicalis nerve to reinnervate the paralyzed larynx. The anatomic course and morphology of the ansa cervicalis are complicated by the variable course and location along the great vessels of the neck, as well as the significant differences observed in the arrangement of its contributing roots and regional branching patterns. Herein, we review the surgical anatomic course of ansa cervicalis and its innervation of the muscles of the neck, and develop specific recommendations with respect to the use of this nerve in laryngeal reinnervation.

Cross-innervation of the thyroarytenoid muscle by a branch from the external division of the superior laryngeal nerve.

The neuroanatomy of the larynx was explored in seven dogs to assess whether there is motor innervation to the thyroarytenoid (TA) muscle from the external division of the superior laryngeal nerve (ExSLN). In 3 animals, such innervation was identified. Electrical stimulation of microelectrodes applied to the ExSLN resulted in contraction of the TA muscle, indicating that this nerve is motor in function. This was confirmed by electromyographic recordings from the TA muscle. Videolaryngostroboscopy revealed improvement in vocal fold vibration following stimulation of the ExSLN compared to without it. Previously, the TA muscle was thought to be innervated solely by the recurrent laryngeal nerve. This additional pathway from the ExSLN to the TA muscle may have important clinical implications in the treatment of neurologic laryngeal disorders such as adductor spasmodic dysphonia.

Vocal function following vertical hemilaryngectomy: comparison of four reconstruction techniques in the canine.

The goals of laryngeal reconstruction have been prevention of aspiration, production of a functional voice, and maintenance of an adequate airway for decannulation. A number of procedures for partial laryngeal reconstruction have accomplished these objectives. However, few studies have attempted to compare patients' vocal characteristics following different reconstruction procedures. In this study, an in vivo canine model was used to compare acoustic and aerodynamic measures of vocal function for the following vertical hemilaryngectomy reconstruction techniques: 1) a superiorly based sternohyoid muscle flap, 2) a modified epiglottic laryngoplasty, 3) a new procedure using a layered vascularized buccal mucosal flap and a transversely oriented sternohyoid muscle flap, and 4) hemilaryngeal transplantation combined with arytenoid adduction. Hemitransplantation provided the most efficient phonation of the four techniques. The vascularized buccal mucosa flap produced the best phonation of the autologous tissue techniques examined. Both vascularized buccal mucosa flap and hemilaryngeal transplantation subjects demonstrated a mucosal wave on stroboscopy. The results indicate that vocal function will improve as the layered structure of the vocal fold is more accurately replicated in a reconstructed hemilarynx. Endoscopic findings and whole organ sections are presented.

Physiologic motion after laryngeal nerve reinnervation: a new method.

In this study a new method of reinnervation for unilateral recurrent laryngeal nerve paralysis was performed in canines, producing physiologic vocal fold motion in each of a small series of animals. During the procedure the left anterior division of the recurrent laryngeal nerve was reinnervated with axons from the thyroarytenoid branch of the contralateral recurrent laryngeal nerve. The posterior branch of the left recurrent laryngeal nerve was divided and sutured to the ansa cervicalis to maintain tone in the posterior cricoarytenoid muscle. In all four animals, the right distal vocalis stump was reinnervated with an ansa cervicalis nerve branch. After 3 months physiologic vocal fold motion and electromyographic activity could be demonstrated during mechanical stimulation of the supraglottis (adduction) and during tracheostomy obstruction (abduction). Acoustic data revealed improvement of jitter, shimmer, signal-to-noise ratio, and vocal efficiency in reinnervated animals compared with paralyzed canines before treatment, although the results lacked statistical significance. This approach to the rehabilitation of unilateral vocal fold paralysis is discussed.