Cheryl L. Rainey

Electrical Pacing of the Paralyzed Human Larynx

This study represents the first attempt to electrically pace the paralyzed human larynx. The goal was to determine if electrical stimulation of the posterior cricoarytenoid muscle could produce functional abduction of the vocal fold in pace with inspiration. An external apparatus was used to sense inspiration and reanimate the unilaterally paralyzed larynx of a thyroplasty patient. Stimuli were delivered through a needle electrode to locate and pace the abductor muscle. The magnitude of electrically induced abduction was comparable to spontaneous movement on the normal side. The abduction was appropriately timed with inspiration; this finding demonstrated that this simple pacing system could effectively modulate stimulation with patient respiration.

Recurrent Laryngeal Nerve Avulsion for Treatment of Spastic Dysphonia

Treatment of spastic dysphonia by recurrent laryngeal nerve section has resulted in reproducibly good results in the early postoperative period in most patients. However, critical long-term follow-up has shown a high recurrence rate of adductor spasms by the third year after initial nerve section. A patient who developed recurring adductor spasms 1 year after nerve section was reexplored, with identification of neural regrowth into the distal segment of the recurrent laryngeal nerve. The technique of neural avulsion removing the distal nerve up to its insertion into the laryngeal muscles is described. Neural regrowth, which is just one of the possible mechanisms for recurrence of spastic dysphonia, should be prevented by this surgical modification. Twelve patients who have undergone neural avulsion primarily for spastic dysphonia are being followed up without recurrence of symptoms thus far. Although these results appear promising, this short follow-up that averages 1.5 years must be extended to firmly support these concepts.

Technical Approach for Reanimation of the Chronically Denervated Larynx by Means of Functional Electrical Stimulation

Functional electrical stimulation (FES) of the posterior cricoarytenoid (PCA) muscle to produce vocal fold abduction offers an alternative approach to current surgical therapies for bilateral vocal fold paralysis. The purpose of this study was to characterize the application of FES to chronically denervated PCA muscles. Specific goals were to develop a stimulus delivery system for the PCA muscle, determine a practical means of implantation, and identify stimulus parameters effective in activating chronically denervated muscle. Seventeen dogs were implanted with planar electrode arrays 3 months after unilateral recurrent laryngeal nerve resection. A nail-bed electrode array allowed discrete activation of the PCA muscle and gave the greatest abductions, with minimal charge dissipation. Muscle mapping revealed hot-spot regions on the PCA muscle surface, in which stimulation produced maximum abduction. A conservative stimulus paradigm effective in activating chronically denervated muscle was a 1-second pulse train of 2-millisecond-duration pulses, delivered at a tetanizing frequency of 30 Hz and an amplitude of 4 to 14 mA.

Lateral Laryngotomy for the Removal of Teflon Granuloma

Teflon injection has been used for vocal fold medialization following paralysis. Recently, numerous articles have discussed the complications of Teflon injection, including overinjection, airway obstruction, Teflon granuloma, and an abnormal mass effect creating a decreased vibratory character of the true vocal fold. Multiple techniques for Teflon removal have been described. This report details our experience with complete Teflon granuloma removal via a lateral laryngotomy under local anesthesia. Microscopic dissection of the entire granuloma and the paraglottic space was accomplished in all patients. Due to extensive destruction caused by the granuloma, the vocal ligament was resected in 3 patients; it was partially resected and reanastomosed in 1 case, and spared in 6 patients. Laryngeal reconstruction was accomplished with an inferiorly based sternohyoid muscle rotation flap and arytenoid adduction. Effortful speech secondary to pressed vocal quality resolved in all patients. Near-normal to normal vocal quality was obtained in 4 patients, with the average “voice desirability” improving 60% and the effective glottic width increasing 29%. Factors that contributed to a successful outcome included noninvolvement of the vocal ligament and sparing of the mucosal cover.

Long-Term Follow-up of Recurrent Laryngeal Nerve Avulsion for the Treatment of Spastic Dysphonia

Long-term follow-up of 3 to 7 years is reported on 18 patients who had undergone recurrent laryngeal nerve avulsion (RLNA) for the treatment of adductor spastic dysphonia (SD). Data on neural regrowth after previous recurrent laryngeal nerve section (RLNS) are presented in 2 of these 18 patients. We introduced RLNA as a modification of standard RLNS to prevent neural regrowth to the hemiparalyzed larynx and subsequent recurrence of SD. We have treated a total of 22 patients with RLNA, and now report a 3- to 7-year follow-up on 18 of these 22 patients. Resolution of symptoms was determined by routine follow-up assessment, perceptual voice analysis, and patient self-assessment Sixteen of 18, or 89%, had no recurrence of spasms at 3 years after RLNA as determined at routine follow-up. Two of the 16 later developed spasms after medialization laryngoplasty for treatment of weak voice persistent after the avulsion. This yielded a total of 14 of 18, or 78%, who were unanimously judged by four speech pathologists to have no recurrence of SD at the longer follow-up period of 3 to 7 years. Two of these 4 patients were judged by all four analysts to have frequent, short spasms. The other 2 were judged by two of four analysts to have seldom, short spasms. Three of 18 patients presented with recurrent SD after previous RLNS. At the time of subsequent RLNA, each patient had evidence of neural regrowth at the distal nerve stump as demonstrated by intraoperative electromyography and histologic evaluation of the distal nerve stump. One remained free of SD following RLNA, 1 was free of spasms at 4 years after revision avulsion but developed spasms after medialization laryngoplasty, and the final patient developed spasms 3.75 years after revision RLNA. Medialization laryngoplasty with Silastic silicone rubber was performed in 6 of 18, with correction of postoperative breathiness in all 6, but with recurrence of spasm in 3. Spasms resolved in 1 of these with downsizing of the implant. We conclude that RLNA represents a useful treatment in the management of SD in patients not tolerant of botulinum toxin injections.

11:45 AM: Electrical Pacing of the Paralyzed Human Larynx

trodes, and (3) glycogen-depletion assay was quantified using digitized computer-image analysis of those laryngeal muscle fibers staining positive for PAS. Results: A significant doses effect relationship was observed in the vocal fold motion, as was spontaneous activity of laryngeal muscles. Botulinum toxin affected the posterior cricoarytenoid muscle with doses exceeding 0.001 U. Image analysis assay demonstrated that the staining intensity of noninjected muscle was less than that of the injected muscle. Conclusion: This work will serve as a baseline for establishing a response matrix to be used in identifying favorable treatment patterns for botulinum toxin injection and demonstrating the effects of repeated laryngeal injections.

Voice Response to Injection of Succinylcholine in the Thyroarytenoid Muscle of Normal Subjects

Botulinum toxin (Botox) is commonly used in the treatment of spasmodic dysphonia. Succinylcholine is a neuromuscular blocking agent that mimics the biological activity of Botox yet takes effect wit...

Biological Activity of Botulinum Toxin Type A in the Chronically Implanted Rat

It is well known that the larynx has three functions: phonation, lower airway protection, and respiration. Many studies have explored the mechanisms of phonatory function and lower airway protection of the larynx, whereas there have been few studies dealing with laryngeal respiratory function. Recently it was revealed that the sensory afferents from the larynx transmit to the medullary respiratory neurons and affect respiratory rhythmogenesis. Furthermore, some studies have reported an interaction between the medullary respiratory neurons and laryngeal motoneurons located in the nucleus ambiguus. From these findings it was suggested that the larynx participates in respiration actively and influences respiratory regulation. Therefore we studied the changes in the activity of the intrinsic laryngeal muscles during hypercapnia in the decerebrated cat. The electromyographic activity of the posterior cricoarytenoid and lateral cricoarytenoid muscles were recorded simultaneously with an electromyogram of the diaphragm, intratracheal pressure, and endotracheal partial concentration of 02 and CO 2. Hypercapnia was induced by inhalation of CO 2 gas, and the end-tidal CO 2 was maintained at 8% to 10%. The activity of the intrinsic laryngeal muscles during hypercapnia was analyzed in comparison with that during eucapnia. In hypercapnia, both the posterior cricoarytenoid and lateral cricoarytenoid muscles increased their electromyographic activities, and the intratracheal pressure during expiration was elevated to a higher level than that in eucapnia. These findings suggested a further widening of the glottis during inspiration to decrease inspiratory resistance and a further narrowing of the glottis during expiration to prevent alveolar collapse. Thus it may be concluded that the larynx actively participates in respiratory regulation under the control of the brain stem.