Effects of Cricothyroid Muscle Contraction on Laryngeal Resistance and Glottic Area

To determine the functional significance of the cricothyroid muscle (CT) in respiration, laryngeal resistance was measured in anesthetized dogs, along with electromyographic activity of the posterior cricoarytenoid muscle (PCA) and CT. In two dogs the larynx was videotaped simultaneously via a telescope. Increased CT activity was induced by airway occlusion or hypercapnia. Observations were carried out before and during cold blockade of the recurrent laryngeal nerve (RLN) or the nerve to the CT (external branch of the superior laryngeal nerve [Ext SLN]). Paralysis of the CT had no effect on laryngeal resistance or glottic area, even at very high levels of CT activity. Blockade of the RLN increased inspiratory resistance, but did not have a significant effect on expiratory resistance. Electrical stimulation of the Ext SLN produced tetanic CT contraction, which increased laryngeal resistance in both inspiration and expiration. This was true even at very high levels of PCA activity. These results indicate that although artificially induced CT contraction markedly affects laryngeal resistance, physiologic levels of respiratory activity do not have a significant effect.

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Effects of Recurrent Laryngeal Nerve Transection and Vagotomy on Respiratory Contraction of the Cricothyroid Muscle

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948909800512 ◽

1989 ◽

Vol 98 (5) ◽

pp. 373-378 ◽

Cited By ~ 6

Author(s):

Gayle E. Woodson

Keyword(s):

Recurrent Laryngeal Nerve ◽

Superior Laryngeal Nerve ◽

Upper Airway ◽

Vocal Folds ◽

Laryngeal Nerve ◽

Electromyographic Activity ◽

Airway Occlusion ◽

Cricothyroid Muscle ◽

Bilateral Vagotomy ◽

Posterior Cricoarytenoid

The cricothyroid muscle (CT) appears to be an accessory muscle of respiration. Phasic inspiratory contraction is stimulated by increasing respiratory demand. Reflex activation of the CT may be responsible for the paramedian position of the vocal folds, and hence airway obstruction, in patients with bilateral recurrent laryngeal nerve (RLN) paralysis. Previous research has demonstrated the influence of superior laryngeal nerve (SLN) afferents on CT activity. The present study addresses the effects of vagal and RLN afferents. Electromyographic activity of the CT and right posterior cricoarytenoid muscle was monitored in anesthetized cats during tracheotomy breathing and in response to tracheal or upper airway occlusion in the intact animal. This was repeated following left RLN transection, bilateral vagotomy, and bilateral SLN transection. Vagotomy abolished CT response to tracheal occlusion and markedly reduced the response to upper airway occlusion. Vocal fold position following RLN transection appeared to correlate with CT activity; however, observed changes were minor.

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Thyroid cartilage movements during breathing

Journal of Applied Physiology ◽

10.1152/jappl.1995.78.2.441 ◽

1995 ◽

Vol 78 (2) ◽

pp. 441-448 ◽

Cited By ~ 5

Author(s):

T. C. Amis ◽

A. Brancatisano ◽

A. Tully

Keyword(s):

Electrical Stimulation ◽

Recurrent Laryngeal Nerve ◽

Thyroid Cartilage ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Electromyographic Activity ◽

Tidal Breathing ◽

Left And Right ◽

Posterior Cricoarytenoid ◽

Stimulation Of

We measured lateral (outward) thyroid cartilage displacement (TCD) of the larynx in six supine anesthetized (intravenous chloralose) dogs. Combined left and right TCDs were measured with linear transducers attached by a thread to the thyroid alae. During tidal breathing via a tracheostomy, phasic inspiratory TCD occurred in all dogs [0.66 +/- 0.2 mm (mean +/- SE)] together with phasic inspiratory electromyographic activity in the cricothyroid (CT) and posterior cricoarytenoid (PCA) muscles. During brief tracheal occlusions, TCD increased significantly to 1.27 +/- 0.2 mm (P = 0.001), accompanied by an increase of 95–115% in the peak CT and PCA electromyograms. Bilateral supramaximal electrical stimulation of the external branches of the superior laryngeal nerve (ExSLN) produced a TCD of 9.9 +/- 0.8 mm; however, similar stimulation of the recurrent laryngeal nerve (RLN) produced a TCD of only 1.33 +/- 0.1 mm (P = 0.0001). Furthermore, bilateral section of the ExSLN in five dogs significantly reduced tidal TCD by 48.7 +/- 24.4% (P < 0.05), and bilateral section of both the ExSLN and RLN resulted in slight phasic inward TCD (-0.06 +/- 0.05 mm). Thus, it appears that the activities of both the CT and RLN-innervated muscles (probably the PCA muscle) contribute to tidal breathing TCD. These findings suggest that inspiratory dilation of the hypopharynx is mediated by contractions of CT and PCA muscles.

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Can we routinely identify the external branch of the superior laryngeal nerves with neural monitoring?: a prospective report on 176 consecutive nerves at risk

Updates in Surgery ◽

10.1007/s13304-021-01084-6 ◽

2021 ◽

Author(s):

Paolo Del Rio ◽

Elena Bonati ◽

Tommaso Loderer ◽

Matteo Rossini ◽

Federico Cozzani

Keyword(s):

Voice Quality ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Muscle Twitch ◽

Cricothyroid Muscle ◽

Emg Signal ◽

External Branch ◽

Mode Of Application ◽

Neural Monitoring ◽

Intermittent Mode

AbstractThe external branch of the superior laryngeal nerve (EBSLN) provides motor function to the cricothyroid muscle (CTM). EBSLN damage produces changes in voice quality and projection. Intraoperative neuromonitoring (IONM) in thyroid surgery aims to optimize EBSLN control during dissection. We prospectively collected the data of 88 consecutive patients who underwent total thyroidectomy with IONM from July 2019 to December 2019. IONM was offered in the intermittent mode of application. We routinely searched for the EBSLN electromyographic (EMG) signal before (S1) and after (S2) dissection of the superior vascular peduncle. In the absence of the EMG signal, we observed the CTM twitch. We identified 141 (80%) S1 EMG signals, while we recorded the CTM twitch in 15 cases (8.5%). In 20 (11.3%) cases, we were unable to identify the EMG signal. Analysing the S2 results, we found loss of EBSLN signal in 11/141 cases (7.8%) identified with IONM in pre-dissection stimulation. Among the 20 cases without pre-dissection identification (we had not identified the external branch of the superior laryngeal nerve or the muscle twitch), in the post-dissection evaluation, we confirmed the loss of signal in 17 of 20 cases, equal to 85% (p < 0.001). Our data clearly show that intraoperative stimulation and recognition of EBSLN, performed before any dissection manoeuvre to the superior vascular thyroid pole, leads to a much higher rate of nerve conservation.

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Newer Techniques of Laryngeal Reinnervation

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948909800103 ◽

1989 ◽

Vol 98 (1) ◽

pp. 8-14 ◽

Cited By ~ 6

Author(s):

Anthony J. Maniglia ◽

Brian Dodds ◽

Kelly Sorensen ◽

N. Kumar ◽

M. B. Katirji

Keyword(s):

Vocal Cord ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Control Group ◽

Pedicle Flap ◽

Motor Branch ◽

Cricothyroid Muscle ◽

Vocal Cord Mobility ◽

Posterior Cricoarytenoid ◽

The Right

We relate the experience obtained in the use of the right superior laryngeal nerve (motor branch)–cricothyroid muscle pedicle flap in dogs in an attempt to reinnervate the right posterior cricoarytenoid muscle (PCA). The right vocal cord was paralyzed by severance and removal of 2.5 cm of the right recurrent laryngeal nerve. Evaluation 6 months postoperatively revealed the vocal fold remobilization on the right side to have an average of about one half the mobility of the left, normal side. After the recurrent laryngeal and superior laryngeal nerves on the left were severed, the vocal cord mobility dropped to only about one fourth. This suggests that the dogs had contralateral reinnervation. Nevertheless, the right vocal cord mobility, driven only by the right superior laryngeal nerve, was enough to secure an adequate airway without the need for a tracheotomy. This experiment was statistically significant on comparison with a control group. Electromyographic studies as well as PCA histochemistry were performed.

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External Branch of the Superior Laryngeal Nerve: Applied Surgical Anatomy and Implications in Thyroid Surgery

The American Surgeon ◽

10.1177/000313481207800940 ◽

2012 ◽

Vol 78 (9) ◽

pp. 986-991 ◽

Cited By ~ 10

Author(s):

George H. Sakorafas ◽

Panayiotis Kokoropoulos ◽

Christos Lappas ◽

Dimitrios Sampanis ◽

Vassilios Smyrniotis

Keyword(s):

Thyroid Surgery ◽

Full Range ◽

Superior Laryngeal Nerve ◽

Surgical Anatomy ◽

Laryngeal Nerve ◽

Injury Incidence ◽

High Frequencies ◽

Cricothyroid Muscle ◽

External Branch ◽

Operating Surgeon

The external branch of the superior laryngeal nerve (EBSLN) is the only motor supply to the cricothyroid muscle and has an important role during phonation in high frequencies. Iatrogenic injury of the EBSLN, most commonly during thyroid surgery, is associated with varying levels of alterations in phonation, which may have an impact on a patient's life, especially when his or her career depends on the full range of voice. EBSLN injury incidence after thyroid surgery ranges widely in the literature (0 to 58%). Despite this wide variation, it appears that EBSLN injury is a not uncommon, and frequently overlooked, complication of thyroid surgery. An in-depth knowledge of the surgical anatomy of the EBSLN is therefore required from the part of the operating surgeon to protect this nerve during thyroid surgery.

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Innervation of the human posterior cricoarytenoid muscle by the external branch of the superior laryngeal nerve

Head & Neck ◽

10.1002/hed.24896 ◽

2017 ◽

Vol 39 (11) ◽

pp. 2200-2207 ◽

Cited By ~ 2

Author(s):

Mehmet Uludag ◽

Nurcihan Aygun ◽

Kinyas Kartal ◽

Evren Besler ◽

Adnan Isgor

Keyword(s):

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

External Branch ◽

Posterior Cricoarytenoid Muscle ◽

Posterior Cricoarytenoid

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Characteristics of Late Responses to Superior Laryngeal Nerve Stimulation in Humans

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348949210100204 ◽

1992 ◽

Vol 101 (2) ◽

pp. 127-134 ◽

Cited By ~ 78

Author(s):

Christy L. Ludlow ◽

Frederick Van Pelt ◽

Junji Koda

Keyword(s):

Muscle Activation ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Onset Latency ◽

Internal Branch ◽

Cricothyroid Muscle ◽

External Branch ◽

Muscle Responses ◽

Thyroarytenoid Muscle ◽

Stimulation Of

To characterize human thyroarytenoid and cricothyroid muscle responses to stimulation of the internal (sensory) and external (motor) branches of the superior laryngeal nerve (SLN), three awake subjects were studied at rest and during muscle activation with stimulation at different current levels. When only the external branch was stimulated, direct cricothyroid muscle responses were obtained without responses in either thyroarytenoid muscle. When only the internal branch was stimulated, no cricothyroid responses were obtained, but two late thyroarytenoid responses occurred (R1 and R2). The R1 response was usually ipsilateral and had a mean onset latency of 18 milliseconds, while the R2 response was bilateral and occurred between 66 and 70 milliseconds. Both responses tended to decrease in latency and increase in amplitude with increased stimulation level. The similarity of Rl to the adductor response and R2 to other late responses is discussed.

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Comparative analysis of voice changes after thyroidectomy; mass versus individual ligation of superior thyroid artery with reference to identification of external branch of superior laryngeal nerve

International Journal of Otorhinolaryngology and Head and Neck Surgery ◽

10.18203/issn.2454-5929.ijohns20202217 ◽

2020 ◽

Vol 6 (6) ◽

pp. 1155

Author(s):

Sunil Samdani ◽

Shweta Dudi ◽

Veena Mobarsa

Keyword(s):

Superior Laryngeal Nerve ◽

Close Relation ◽

Laryngeal Nerve ◽

Controlled Study ◽

Superior Thyroid Artery ◽

Cricothyroid Muscle ◽

External Branch ◽

Group B ◽

The Impact ◽

Superior Pole

Background: The external branch of the superior laryngeal nerve innervates the cricothyroid muscle to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels puts the external branch of the superior laryngeal nerve in risk every time the superior pole of the thyroid is dissected.Methods: : This randomized controlled study was undertaken at SMS Medical College, Jaipur between February 2013 to November 2014 to evaluate the impact of isolating and ligating the superior thyroid vessels near the upper pole of the gland as compared to conventional mass ligation of the superior pole regarding external branch of superior laryngeal nerve injury in hemi or subtotal thyroidectomy. Total 120 patients were taken and divided into two groups A and B. Group A including mass ligation of superior pole of thyroid and group B includes individual ligation of superior thyroid vessels. Results: Our study observed normal voice in 51 cases (85%) in individual ligation of superior thyroid vessel group and 27 cases (45%) in mass ligation group on auditory perceptual test by GRBAS scale one month postoperatively. Normal electromyography findings after 1 month post-operatively was observed in 57 cases (95%) in individual ligation group as compared to 40 cases (66.67%) in mass ligation group.Conclusions: Our study conclude that careful ligation of superior thyroid vessels is a safe technique to preserve the external branch of superior laryngeal nerve than mass ligation of superior pole of thyroid.

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