Garrett D. Herzon

Reanimation of the Paralyzed Human Larynx With an Implantable Electrical Stimulation Device

Objectives/Hypothesis Electrical stimulation of the posterior cricoarytenoid muscle, when paced with inspiration, offers a physiological approach to restore ventilation in bilateral laryngeal paralysis without any of the disadvantages associated with conventional treatment.

Effects of denervation on laryngeal muscles: A canine model

The purpose of this study was to chronologically evaluate the changes in function and histomorphometry of denervated laryngeal muscles. In 14 adult mongrel dogs, a 2.5‐cm segment of the right recurrent laryngeal nerve was excised. Videolaryngoscopy and electromyography were performed at 1, 2, 3, 4, 5, 6, and 9 months under intravenous sedation. The animals were then killed, and the laryngeal muscles were processed for histochemical reactions. The mean muscle fiber diameter, standard deviation, and muscle fiber type composition were determined. The findings indicate that, following recurrent laryngeal nerve sectioning, the canine intrinsic laryngeal muscles undergo denervation atrophy for approximately 3 months, after which reinnervation occurs. The source of reinnervation appears to be from regenerated nerve fibers of the sectioned recurrent laryngeal nerve. The nerve fibers nonselectively reinnervated the abductor and adductor muscles of the larynx.

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.

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.

Clinical Measurement of Mucosal Wave Velocity Using Simultaneous Photoglottography and Laryngostroboscopy

Simultaneous glottal transillumination or photoglottography (PGG), electroglottography (EGG), and video laryngostroboscopy were used to measure the traveling wave velocity of the vibrating vocal folds during phonation in human subjects. The duration of travel was calibrated from the PGG signal, while the displacement of the upper and lower lips of the vibrating vocal folds was calibrated from parallel laser beams projected onto the vocal folds. The mucosal wave velocity varied with the portion of the glottal cycle. The amplitude of displacement correlated positively with the intensity of phonation and negatively with the fundamental frequency and was decreased for breathy and pressed phonation modes. The velocity of the opening phase segment of the PGG signal directly correlated with the top lip displacement of the vibrating vocal fold, and bottom lip displacement correlated with the closing phase of the PGG signal. Therefore, with suitable calibration, the effects of mucosal lateral displacement may be measured from a PGG signal. Simultaneous measures of PGG, EGG, and stroboscopy provide a three-dimensional representation of glottal vibration that can be numerically analyzed.

Laser‐Assisted Uvulopalatoplasty and Tonsillectomy for the Management of Obstructive Sleep Apnea Syndrome

Objectives/Hypothesis Laser‐assisted uvulopalatoplasty (LAUP) is a widely accepted procedure for the management of snoring, but its role in the treatment of obstructive sleep apnea syndrome is currently unclear. The objective of the study was to evaluate the role of LAUP in treating moderate and severe obstructive sleep apnea syndrome.

The effects of chronic electrical stimulation on laryngeal muscle reinnervation

The present study examined the effects of functional neuromuscular stimulation (FNS) on reinnervation of the posterior cricoarytenoid (PCA) muscle. In 4 canines, the recurrent laryngeal nerve (RLN) was sectioned and anastomosed and a patch electrode array implanted for stimulation and recording at multiple PCA sites. Following implantation, FNS was applied to 2 canines for a period of 6 weeks. Two additional animals served as nonstimulated controls. In each animal, histomorphometric analysis of the RLN was used to assess the quality of nerve regeneration and the potential for muscle reconnection. The magnitude of reinnervation was monitored by electromyographic (EMG) potentials evoked by RLN stimulation. The appropriateness of reconnection was determined by the pattern of spontaneous EMG activity and recovery of vocal fold abduction. Results of this preliminary study indicated that FNS caused an overall repression of reinnervation. However, the repression preferentially inhibited reconnection by foreign nerve fibers, promoting selective reinnervation and preventing synkinesis.

Complications in the Approach to Acoustic Tumor Surgery

Earlier diagnosis and cooperation with allied specialists in neurosurgery have lessened complications of acoustic tumor surgery. To date, complications cannot always be prevented. The controversy over which approach is best for acoustic tumor extirpation still continues. While teams must answer this question themselves, our experience favors the transtemporal approach. Of the potential disabilities from this operation, facial paralysis or its sequelae remain the most frequent. The transtemporal approach gives a more accurate anatomical definition of the facial nerve. Efforts to preserve hearing (especially with tumors 2 cm or larger), when matched with the potential sequelae of facial paralysis, may prove futile.

The Effects of Chronic Electrical Stimulation on Laryngeal Muscle Physiology and Histochemistry

The present study examined the effects of functional neuromuscular stimulation (FNS) on posterior cricoarytenoid (PCA) muscle physiology and histochemistry. In 4 canines, 10 cm of the recurrent laryngeal nerve was resected. A patch electrode array was implanted for PCA stimulation. FNS was applied to 2 canines for a period of 4 weeks with 2 additional animals serving as nonstimulated controls. Results indicated that FNS increased PCA muscle contractility over the period of intervention but had no effect on contraction speed. FNS also protected the muscle from atrophy by preventing muscle weight loss and type 2 fiber deterioration. Finally, it rescued muscle fibers from ensuing fibrosis.

Facial nerve antidromic recordings in patients with Bell's palsy.

Antidromic facial nerve action potentials have been recorded noninvasively from the tympanic membrane (TM) of patients with Bells palsy. A standardized approach has been developed in normal subjects that involves differential recording between the TM and adjacent canal wall. A metal annulus on the tip of an ear speculum served as the reference electrode. The speculum was held in place by an adjustable headband. A conductive sponge electrode inserted through the speculum served as the active TM electrode. In clinical trials, nerve potentials recorded from the paralyzed side were abnormal in all patients tested, indicating that nerve pathology could be monitored with this technique. Abnormalities were evident at the first test, within the first day of paralysis for some patients, and well in advance of any abnormality in the electroneuronography (ENoG) response. There appeared to be a relationship between specific waveform abnormalities (e.g., increased peak latency, waveform temporal dispersion, decreased area) and the tendency for a patient to recover from paralysis. These observations suggest that the technique described could serve as a means for early prognosis, at a stage in which nerve damage could still be effectively treated.