Intraoperative measurement of the elastic modulus of the vocal fold. Part 1. Device development.

Although the concept of manipulating laryngeal biomechanics to improve vocal function is not new, there has been a recent proliferation in surgical techniques used to affect laryngeal function. These include methods which increase the stiffness of the vocal folds, medialize the vocal folds, alter the pitch by changing the tension of the vocal folds, and augment the tissues using injection of alloplastic materials. Despite these new and possibly revolutionary methods, no means are presently available to surgeons to intraoperatively evaluate and optimize results of a surgical intervention. This study involved the development of a device to measure the in vivo elastic modulus of the vocal folds.

Photoelectric measurement of laryngeal paralyses correlated with videostroboscopy.

Photoglottography and electroglottography are relatively noninvasive techniques that provide detailed information about vocal fold vibration. However, few significant clinical applications have been made by correlating photoelectric waveforms to specific pathologic changes in laryngeal vibration. Videostroboscopy has recently been used to document vibratory patterns of laryngeal paralyses in a canine model of phonation. A study of PGG and EGG waveforms correlated with videostroboscopy in an in-vivo canine model of phonation with simulated unilateral recurrent or superior laryngeal nerve paralysis is presented. The shift quotient--a new glottographic parameter which identifies flaccid laryngeal paralyses--is presented.

Intraoperative measurement of the elastic modulus of the vocal fold. Part 2. Preliminary results.

This paper presents initial clinical experience using a device capable of measuring the transverse elastic modulus of the vocal fold. These initial results indicated that the device may be useful in determining stiffness inequalities between the vocal folds.

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.

An in vivo canine model for testing treatment effects in laryngeal hyperadduction disorders.

Adductor spastic dysphonia is a voice disorder characterized by a strained, squeezed, effortful voice produced by true and false cord hyperadduction. An in vivo canine model has been developed to simulate hyperadduction of the true cords. Using this model, the thyroarytenoid muscle was found to have a greater effect on intraglottic and subglottic pressure than cricothyroid muscle contraction. The intraglottic and subglottic pressure was reduced after simulated recurrent laryngeal paralysis. This model can be used in future studies to compare laryngeal treatment modalities for disorders that have a component of vocal cord hyperadduction, such as spastic dysphonia.

Parotid hypertrophy with bulimia: a report of surgical management.

Benign hypertrophy of the salivary glands can occur in patients with anorexia nervosa. This enlargement has been related to nutritional deficiencies and bulimia, which is a form of episodic binge eating followed by vomiting. The surgical management of a patient with bulimia and benign bilateral parotid enlargement secondary to bulimia will be discussed. Superficial parotidectomy may be a useful adjunct in managing the cosmetic and psychological aspects of patients with anorexia nervosa and bulimia complicated by massive parotid hypertrophy intractable to medical management.

Treatment of vocal fold granuloma using botulinum toxin type A.

Contact granuloma of the vocal folds has been associated with abnormal use of the voice, and acid reflux may exacerbate the inflammatory process. Treatments have included voice therapy and antireflux measures. Surgical excision is considered in patients who do not respond to medical management. Localized injections of botulinum toxin type A (BOTOX) have been effective in patients with disorders of muscular control in the head and neck. In this study, granulomas resolved in six patients who underwent injection of the affected vocal folds. Botulinum toxin type A is probably successful because it prevents forceful closure of the arytenoids during phonation and coughing. Localized injection of this neurotoxin is promising both as an initial treatment and as an alternative treatment in patients who do not respond to standard therapy or who are poor surgical candidates.

Physiologic motion after vocal cord reinnervation: a preliminary study.

This study attempted to reestablish physiologic vocal cord motion, rather than synkinesis, to a reinnervated 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.

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.

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.

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.

Videostroboscopy of the canine larynx: the effects of asymmetric laryngeal tension.

The effects of simulated paralysis of the peripheral laryngeal nerves on patterns of vocal cord vibrations were studied. Videostroboscopy was used in seven anesthetized mongrel dogs to record laryngeal vibrations during direct electrical stimulation of the recurrent and superior laryngeal nerves under conditions of constant airflow. Stroboscopic images obtained from both supraglottic and subglottic aspects were analyzed frame-by-frame. Results indicated that simulated paralysis of the recurrent laryngeal nerve or combined paralysis of the recurrent and superior laryngeal nerves produced a diminished mucosal wave bilaterally, with loss of the two-mass system of vibration and diminished lateral excursion of the normal cord. In contrast, simulated paralysis of the superior laryngeal nerve was characterized by an abnormally exaggerated vertical movement of the paralyzed cord in relation to the normal cord and a horizontal shifting of the glottis from the paralyzed to the normal side during each vibratory cycle. Clinical implications are discussed and the literature reviewed.

Orthotopic laryngeal transplantation: is it time?

The notion of returning phonatory and respiratory function by transplanting larynges has fascinated and challenged the minds of laryngologists for many years. In the past, the problems of revascularization, tissue rejection, and physiologic vocal fold motion have stymied the success of research in this area. Today, advances in microvascular surgery, graft versus host response, and selective reinnervation have made laryngeal transplantation a theoretical, if not a practical reality. Despite this progress, serious ethical and fiscal considerations remain unresolved. This report will discuss these advances as well as concerns and will present the current UCLA laryngeal physiology laboratory experience with canine laryngeal transplantation.

Determination of vocal fold mucosal wave velocity in an in vivo canine model.

The vocal fold traveling wave is essential to normal voice production. The present investigation examined whether the velocity of the traveling wave (TWV) could be consistently determined in an in vivo canine model and if traveling wave velocity is affected by changes in the amplitude of recurrent laryngeal nerve stimulation (RLNS) and superior laryngeal nerve stimulation (SLNS). The results showed that traveling wave velocity increased with an increase in recurrent laryngeal nerve stimulation at low constant superior laryngeal nerve stimulation, but was poorly correlated with increases in recurrent laryngeal nerve stimulation at a high level of superior laryngeal nerve stimulation. Furthermore, traveling wave velocity was significantly correlated with superior laryngeal nerve stimulation at constant recurrent laryngeal nerve stimulation. This study demonstrated the feasibility of objectively measuring traveling wave velocity in vivo.

Glottographic measures of vocal fold vibration: an examination of laryngeal paralysis.

Photoglottography and electroglottography were applied to groups of patients with recurrent laryngeal nerve paralysis, superior laryngeal nerve paralysis, and combined recurrent and superior laryngeal nerve paralyses of idiopathic causes. Individual patients with resection of the vagal nerve above the origin of the superior laryngeal nerve were also studied. Open Quotient and Speed Quotient were calculated from the photoglottography signals. Speed Quotient values significantly differentiated recurrent laryngeal nerve paralysis from idiopathic paralysis and superior laryngeal nerve paralysis, as well as from normal function. Data from patients with vagal resection clearly differentiated them from patients with recurrent laryngeal nerve paralysis. The measure of Open Quotient distinguished pathological phonation from normal, but was not as useful for separation of differing lesions. Electroglottography appeared to be less useful than photoglottography. The pathophysiology underlying the observed glottographic signals is discussed.

Relation of recurrent laryngeal nerve compound action potential to laryngeal biomechanics.

This study was designed to investigate the compound action potential (CAP) of the recurrent laryngeal nerve (RLN) and to correlate this electrophysiologic signal to laryngeal biomechanics and phonatory function. Four adult mongrel canines were anesthetized. The RLN was isolated and stimulated, and recording electrodes were applied. The electromyographic (EMG) electrode was placed in the thyroarytenoid (TA) muscle. The RLN CAP and the EMG of the TA muscle were recorded and compared to the stimulation intensity, subglottic pressure (Psub), and each other. The CAP peak-to-peak and EMG peak-to-peak amplitudes demonstrated a sigmoidal relation to stimulus intensity and a linear relation to Psub and to each other. On the basis of these findings, the RLN CAP appears to be a reliable physiologic measure of laryngeal function.

Early experience with percutaneous tracheotomy.

Early reports of a percutaneous dilatational technique for tracheotomy tube placement have been encouraging. This method uses a needle for placement into the trachea, a J-tipped guidewire, and progressively larger dilators to widen the stoma for insertion of a tracheotomy tube. A prospective study was undertaken to assess the efficacy of this percutaneous tracheotomy technique. Serious complications were encountered, including difficulty with dilatation, excessive bleeding, false passage of the tracheotomy tube, and death. Because of this unacceptable morbidity, the study was terminated after enrollment of only seven patients. Percutaneous tracheotomy is a dangerous procedure with potential for catastrophic complications. These complications were encountered by third- and fourth-year surgical residents performing the procedure under close supervision. If the puncture technique is further popularized and attempted by untrained physicians, these authors predict many disasters.

Effects of arytenoid adduction on laryngeal function following ansa cervicalis nerve transfer for vocal fold paralysis in an in vivo canine model.

Laryngeal reinnervation with the ansa cervicalis has been proposed as a treatment for human unilateral vocal fold paralysis (UVFP). This study tested the assumption that results from reinnervation could be improved if combined with medialization surgery. Six canine subjects underwent recurrent laryngeal nerve section and reinnervation with a branch of the ansa cervicalis. After reinnervation, vocal function was assessed before and after arytenoid adduction. Although laryngeal function improved significantly following reinnervation, results were significantly enhanced by the addition of medialization surgery. The implications for the treatment of human unilateral vocal fold paralysis are discussed.

Measurement of adductory force of individual laryngeal muscles in an in vivo canine model.

In this experiment, the adductory properties of three intrinsic laryngeal muscles (the thyroarytenoid [TA], lateral cricoarytenoid [LCA], and interarytenoid [IA]) were studied and quantified. Using an in vivo canine laryngeal model, a recently developed "tensionometer" was used to measure the adductory force produced by each of these muscles at the vocal process of the arytenoid. Isolated muscle activation was obtained by stimulating selective terminal branches of the anterior division of the recurrent laryngeal nerve. Results indicate that the LCA is the strongest adductory muscle, followed by the TA and the IA. Videolaryngoscopy revealed that LCA contraction causes adduction of the vocal fold and vocal process, with the predominant effect on the process. TA stimulation leads primarily to adduction of vocal fold, and the IA adducts mainly the vocal process. Implications of these findings are discussed.

Characteristics of an in vivo canine model of phonation with a constant air pressure source.

Many previous studies of laryngeal biomechanics using in vivo models have employed a constant air How source. Several authors have recently suggested that the lung-thorax system functions as a constant pressure source during phonation. This study describes an in vivo canine system designed to maintain a constant peak subglottic pressure (Psub) using a pressure-controlling mechanism. Increasing levels of recurrent laryngeal nerve (RLN) stimulation resulted in a significant rise in resistance followed by a plateau. For a given Psub, flow decreased significantly and precipitously with increasing stimulation and then quickly plateaued. Vocal intensity increased with increasing RLN stimulation until a peak was reached. After this peak, intensity dropped until a plateau was reached, corresponding to the flow minimum. At a given Psub, increasing levels of RLN stimulation resulted in a normal distribution of vocal efficiencies.