Electromyography of Intrinsic Laryngeal Muscles

Abstract

In man during phonation, an increased electrical activity was found in all the intrinsic adductor muscles of the larynx investigated. The change in electrical activity started one‐third to one‐half of a second before audible sound could be recorded by microphone. This latency probably reflects the time necessary to build up a minimum air current and pressure. Whenever it could be discriminated, the maximum frequency of single motor unit discharges was of the order of 20‐50 per second during phonation. This is in contradiction to Husson's theory that the frequency of vibration of the vocal cord during a tone of a given pitch is the result of a corresponding number of impulses to the muscle fibres. During phonation with increasing pitch the electrical activity increased considerably, as long as the increase in pitch occurred within the same register. The increase in electrical activity was adjusted to the level corresponding to a given pitch before the onset of audible sound. The pronounced electrical activity in the adductor muscle in the absence of phonation was inhibited 0 3 sec. before the onset of phonation. This complete inhibition persisted throughout the entire period of voice production. In the abductor muscles also there was a slight activity in the absence of phonation. This activity persisted even when breathing stopped. It was enhanced during inspiration and remained unaltered during expiration. Electromyographical findings are consistent with the assumptions (1) that the vibrational frequency of the vocal cords, and thereby the pitch of the sound produced, is determined by the active and passive tension exerted by the intrinsic laryngeal muscles, and (2) that the active force of sound production is the air pressure, which separates the margins of the glottis with periodic recoil of the vocal cords.

Husson's Theory: An Experimental Analysis of His Research Data and Conclusions

“…These responses are invisible to the naked eye be¬ cause the viscoelastic properties of the mus¬ cle damp its movements at higher stimula¬ tion rates. 19 Depending on the sensitivity of the recording transducer, progressively smaller responses have been elicited in the thyroarytenoideus with stimulation up to 400 cps.72021 However, since they are in¬ visible, they are of no use in natural phona¬ tion. Even Husson agrees that phonation requires visible vocal-fold movements.…”

A method for studying the pharmacodynamic profile of neuromuscular blocking agents on vocal cord movements in anaesthetized cats

“…Contraction of the adductor pollicis muscle is simple and differs markedly from the abduction of the vocal cords. In addition, there are different microanatomical and histological structures and types of innervation (Rossi & Cortesina, 1965;Johnson et al, 1973), which result in different neurophysiological manifestations (Buchthal & Rosenfalck, 1955;Buchthal, 1959) between muscles. Furthermore, differences in muscle temperature and blood supply, presumably responsible for different pharmacokinetic and pharmacodynamic effects at the site of action, i.e.…”

Laryngeal Electromyography: Electrode Guidance Based on 3-Dimensional Magnetic Resonance Tomography Images of the Larynx

“…It was introduced into clinical practice by Weddel et al 1 in 1944 and promoted in the following years by Faaborg-Andersen and Buchthal. 2,3 The percutaneous approach was first performed by Fink et al 4 in 1956 and standardized by Kotby 5 in 1975. Since then, various approaches to the laryngeal muscles have been proposed.…”

“…Since then, various approaches to the laryngeal muscles have been proposed. [2][3][4][5][6] Yet, although safe and usually well tolerated, LEMG has never become routine clinical practice. 7 Reluctance to perform an invasive procedure, limited familiarity with the precise laryngeal muscle anatomy, and lack of electrophysiological understanding probably all account for the limited use of LEMG.…”