Recurrent Laryngeal Nerve Transposition in Guinea Pigs

Abstract

Improved control of prosthetic voice aids for laryngectomees might be possible to obtain with residual laryngeal motor nerve signals. We were able to recover motor signals from the recurrent laryngeal nerve (RLN) by transposing it into the ipsilateral denervated sternohyoid muscle (SH) in 8 guinea pigs. Reinnervation was monitored by electromyographic recordings from surface and intramuscular needle electrodes in awake animals. Within 4 to 14 weeks after surgery, all animals demonstrated laryngeal-like motor activity in the reinnervated SH, including activity during respiration, sniffing, swallowing, and/or vocalizing. After 3 to 6 months, the animals were reanesthetized, and nerve stimulation and section experiments confirmed the RLN as the source of reinnervation in all cases. In several animals, activity of the RLN-innervated SH was demonstrated to be correlated with that of contralateral laryngeal muscles. Histochemical analysis of the SH indicated a unilateral transformation from mostly fatigable to mostly fatigue-resistant fiber types ipsilateral to the RLN transposition, a phenotype more typical of laryngeal muscles. Thus, RLN transposition at the time of laryngectomy may be a method for salvaging laryngeal control signals that could be used to control prosthetic voice devices.

Immunohistochemical Analysis of the Effects of Cross-innervation of Murine Thyroarytenoid and Sternohyoid Muscles

“…Our results in the rat differ substantially from those of Heaton et al (2000) in the guinea pig. These authors showed that the SH in normal guinea pig had 30% of 2a and 2x fibers, together with some slow fibers and an abundance of 2b fibers, but they did not study guinea pig laryngeal muscles.…”

“…Second, there is no fiber atrophy to suggest the presence of denervation; in fact, 2x fibers in cross-innervated SH are 25% larger compared with normal 2x fibers. Cross-innervation of the SH with the RLN has been reported in the guinea pig (Heaton et al 2000), but the focus of that work was not on a possible allotypic difference between laryngeal and somitic muscles. Following such surgery, motor signals of the RLN in relation to respiration and in response to various types of stimuli that elicit laryngeal motor responses could be recorded from the cross-innervated SH, showing that fibers in the RLN retain their laryngeal muscle-specific efferent impulse activity following cross-innervation.…”

The Physiologic Impact of Unilateral Recurrent Laryngeal Nerve (RLN) Lesion on Infant Oropharyngeal and Esophageal Performance

“…In an initial surgery to place markers and electrodes, the right RLN was identified in surgery and dissected to it distal entry into the larynx, and marked with loosely tied suture. In a subsequent lesion surgery, in order to prevent re-innervation of laryngeal muscle [28], the recurrent laryngeal nerve was ligated and crushed with hemoclips in two places, and a 1-3mm section of nerve removed between ligation sites. Nerve lesions were confirmed with post-mortem dissection at the end of the experiment.…”

Assessment of a Method for the Automatic On/Off Control of an Electrolarynx via Lip Deformation

“…To trigger the vibrator automatically, electromyography (EMG) of reserved articulators was used. Heaton et al 9,10 found that the neck surface EMG (sEMG) signal was appropriate for obtaining phonation-related activity after transferring recurrent laryngeal nerves to denervated neck strap muscles. A handsfree EL device controlled by neck strap muscle EMG activity was developed.…”