Michael Broniatowski

Laryngeal pacemaker. II. Electronic pacing of reinnervated posterior cricoarytenoid muscles in the canine

A fully reliable means of rehabilitating patients with bilateral vocal cord paralysis has not yet been developed. In order to improve upon existing solutions to this problem, the authors have recently described a laryngeal pacemaker, initially tested through stimulation of a cross‐over nerve‐muscle pedicle from one sternohyoid muscle to the other in the canine. Afferent stimuli, initiated through elongation of the airway during inspiration, were detected by a linear strain gauge sutured to the tracheal rings and appropriately amplified. The current report deals with the application of this concept to pace a nerve‐muscle pedicle reinnervating the posterior cricoarytenoid muscle. Videoscopie and cinematographic documentation of electrically paced abduction of the reinnervated vocal fold, synchronous with inspiration, was clearly demonstrated. Only miniaturization of an implantable electronic amplifier remains to permit an attempt at pacing of the paralyzed larynx in humans.

Dynamic Laryngotracheal Closure for Aspiration: A Preliminary Report†

Objectives/Hypothesis An estimated 500,000 patients per year in the United States. are affected by stroke‐related dysphagia. Approximately half experience aspiration, which can lead to pneumonia or death. Aspiration may result from many factors, including delayed transport of the bolus, faulty laryngeal elevation, and poor coordination or inappropriate timing of vocal cord closure. Interventions carried out to protect the lungs are usually irreversible, destructive to the upper airway, and rarely prevent the need for enteral tube feeding.

The future of electronic pacing in laryngeal rehabilitation

Fascinating advances are ongoing in the rehabilitation of the incompetent larynx. The advent of microprocessor technology makes possible the construction of potentially implantable devices designed to allow the pacing of various functions of the reinnervated canine larynx. The history of electrical neurostimulation as a technique in laryngeal rehabilitation is reviewed and future human applications discussed in terms of technical feasibility and clinical needs.

Laryngeal Pacemaker. Part I. Electronic Pacing of Reinnervated Strap Muscles lIn the Dog

The best approach to management of bilateral vocal cord paralysis, with its resultant airway compromise, has not yet been universally agreed upon. Recently proposed methods have included direct stimulation of the laryngeal dilators by the modulation of rhythmic information from the chest wall, diaphragm, phrenic nerve, or accessory muscles of respiration. In such an approach, the information obtained is not necessarily related to inspiration only, and direct implantation of a stimulating electrode into the laryngeal musculature may not be fully efficient and tolerated over time. To obviate such difficulties, the authors propose to broaden the concept of electrical pacing by (1) developing a better source for the triggering of electrical activity during inspiration and (2) devising a reliable means of long-term physiologic stimulation of denervated striated muscle not subject to deterioration over time. Such an experimental unit was constructed in the canine. It is based on afferent information that originates from the mechanical lengthening of the trachea during inspiration and is defected through a linear strain gauge sutured to the tracheal rings. The signal obtained is modulated through an impedance detector and is amplified. An efferent limb consisting of a monopolar cuffed electrode placed around a crossover nerve-muscle pedicle from one sternohyoid muscle to the other was used successfully. Such a preliminary experiment with a strap muscle avoids the extraneous factors related to function of the paralyzed larynx. Successful nerve-muscle pedicle pacing, synchronous with respiration, was verified through electromyographic recordings and direct observation in all animals studied.

Improvement of respiratory compromise through abductor reinnervation and pacing in a patient with bilateral vocal fold impairment

To determine whether respiratory compromise from bilateral vocal fold impairment (paralysis) can be objectively alleviated by reinnervation and pacing.

Dynamic rehabilitation of the paralyzed face--II. Electronic control of the reinnervated facial musculature from the contralateral side in the rabbit.

This work is the continuation of a previous pilot study in the rabbit in which motion originating on the face was picked up by miniature strain gages and channeled synchronously to strap muscles reinnervated via crossover nerve-muscle pedicles. In the current series of experiments, we modified the distal limb of the system to reinnervate the previously paralyzed opposite side of the face via an ansa hypoglossi nerve–thyrohyoid muscle pedicle in five animals. Muscular contraction was induced on the intact side by stimulating different branches of the facial nerve, and corresponding information was channeled to the reinnervated side through an upgraded electronic stimulator via monopolar electrodes placed around the nerve pedicle in the neck. In addition to demonstrating perfect synchrony between intact and reinnervated sides, this facial stimulator allowed the reinnervated side of the face to follow the intact side in a graded and sustained fashion, thus demonstrating that fine tuning of reinnervated facial musculature was possible.

Paced glottic closure for controlling aspiration pneumonia in patients with neurologic deficits of various causes.

Objectives We undertook to determine whether paced vocal fold adduction can check aspiration in patients with various neurologic conditions. Methods Five patients with fluoroscopically documented aspiration and repeated pneumonias were enrolled. Two previously reported patients with hemispheric stroke were compared to 3 additional subjects with brain stem-basal ganglia and cerebellar stroke, cerebral palsy, and multiple sclerosis. A modified Vocare stimulator was implanted subcutaneously and linked to the ipsilateral recurrent laryngeal nerve via perineural electrodes. Vocal fold adduction and glottic closure were effected with pulse trains (42 Hz; 1.2 mA; 188 to 560 us) and recorded with Enhanced Image J. Fluoroscopy results with and without stimulation were assessed by 2 independent blinded reviewers. Pneumonia rates were compared before, during, and after the 6- to 12-month enrollment periods. Results There was statistically significant vocal fold adduction (p < 0.05) for all patients, further verified with bolus arrest (p < 0.05 for thin liquids, thick liquids, and puree depending on the speech-language pathologist). Pneumonia was prevented in 4 of the 5 patients during enrollment. In the fifth patient, who had brain stem-basal ganglia and cerebellar stroke, we were unable to completely seal the glottis and open the cricopharyngeus enough to handle his secretions. Conclusions Vocal fold pacing for aspiration pneumonia from a variety of neurologic insults appears to be appropriate as long as the glottis can be sealed. It is not sufficient when the cricopharyngeus must be independently opened.

Contraction patterns of intrinsic laryngeal muscles induced by orderly recruitment in the canine.

The specific performance of intrinsic laryngeal muscles has been difficult to evaluate, especially in living subjects. To reproduce natural contractions, we artificially induced orderly recruitment of their innervating axons according to the size principle. In 5 dogs, both recurrent laryngeal nerves(RLNs) were stimulated with 50 through 10 Hz, 300 to 1000 μA currents while 600 Hz, 1000 to 0 μA decreasing blocking currents were administered. Surface electromyography electrodes placed on the thyroarytenoid, posterior cricoarytenoid, and lateral cricoarytenoid muscles were used to determine the amplitudes (in mA) of compound muscle action potentials. There was a highly statistically significant difference (P<.004) between the thyroarytenoideus which had the fastest rate of recruitment (8.38%), and posterior cricoarytenoideus, which had the slowest (4.81%). There was an intermediate recruitment rate (6.72%) of the lateral cricoarytenoideus, a divergence attributed to a more equal distribution in fast and slow types of myofibers and a smaller sample. We submit that RLN axons can be recruited in an orderly manner according to their sizes and that the rates are unique to the muscle classes they innervate. The parameters defining these contraction patterns may offer key information for laryngeal pacing.

Dynamic Rehabilitation of the Paralyzed Face: I. Electronic Control of Reinnervated Muscles from Intact Facial Musculature in the Rabbit

An entirely satisfactory solution to dynamic rehabilitation of the paralyzed facial musculature has not yet been found. Recent interest in selective reinnervation of the laryngeal musculature, synchronous with appropriate afferent information, has led us to propose that miniature strain gauges be placed on one or more muscles of facial expression on the intact side to channel electrical signals to the opposite corresponding facial musculature reinnervated via nerve-muscle pedicles. In order to avoid introducing extraneous factors related to facial motion, this principle was first studied on crossover ansa hypoglossi nerve-muscle pedicles in New Zealand white rabbits. Surgery was performed on a total of five animals that were under general anesthesia with xylazine and ketamine, through a midline neck incision. The animals were reexplored after 12 weeks, and after verification that reinnervation had taken place, a vertical incision was made under the external canthus, in order to expose the facial nerve. A miniature strain gauge was then sutured on the facial musculature and connected to a central modulating unit that was, in turn, linked to the nerve-muscle pedicle via a monopolar electrode. Facial wiggle that resulted from direct electrical facial nerve stimulation caused synchronous contraction of all reinnervated strap muscles under study; this was documented on film and through facial and strap muscle activity tracings. Our next step will be to extend this principle to paralyzed facial muscles. If successful, this system could be miniaturized for long-term implantation in human beings.

Artificial reflex arc: A potential solution for chronic aspiration: II. A canine study based on a laryngeal prosthesis†

Long‐term and repeated aspiration can result in pneumonia and eventually death. To avoid current techniques which divert or close off the incompetent larynx, the authors have recently described an artificial reflex arc (ARA), in hopes of providing a dynamic solution to this problem. With this concept, a segment of skin surface with intact sensory innervation is implanted into the pharynx in the path of the food bolus. Resulting neural impulses would be detected by a perineural electrode and then channeled to both recurrent laryngeal nerves via an electronic pacemaker to cause vocal fold adduction at the critical time during swallowing. A pilot study using a tubed cervical cutaneous surface has yielded promising results in the canine. In this current study, an alternate means for information pickup based upon use of a miniature strain gage is presented. Mechanical stimulation of the hypopharynx using this “sensory” detector resulted in synchronous laryngeal adduction of the vocal folds, as documented graphically and on videotape.