Protocol for Neurophysiological Studies of the Superior and Recurrent Laryngeal Nerves and of the Cricothyroid and Thyroarytenoid Muscles. Clinical Utility (original) (raw)
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SiSli Etfal Hastanesi Tip Bulteni / The Medical Bulletin of Sisli Hospital, 2016
The effect of the intraoperative neuromonitoring to the external branch of the superior laryngeal nerve identification and contribution of the nerve to the motor function of the thyroaritenoid muscle Objective: Meticulous anatomical studies of cadaver larynges revealed terminal branches of the external branch of the superior laryngeal nerve (EBSLN) reaching the anterior thyroarytenoid muscle (TA) region and communicating with branches of the recurrent laryngeal nerve (RLN) in 41% to 85% of cases. This nerve is called "human communicating nerve". Although the visual identification of the RLN is accepted to be the gold standart to preserve the nerve, there is still not a standart technique to preserve the EBSLN. In this study; we aimed to evaluate the intraoperative neuromonitoring's (IONM) contribution to visual and functional identification of EBSLN, and the nerve's contribution to the TA muscle function electrophysiologically. Material and Methods: The prospective data of 50 consecutive (42F, 8M) patients, who underwent thyroid surgery with IONM for the exploration of EBSLN, were evaluated. The surface endotracheal tube-based Medtronic NIM3 (Medtronic, Jacksonwille, FL) IONM device was used. The function of EBSLN was evaluated by cricothyroid muscle twitch. Additionally, EBSLN's contribution to the vocal cord adduction was evaluated by the electromyographic records. Results: Fourty one patients were bilaterally and 9 were unilaterally intervented. Eighty four (92.3%) of 91 EBSLNs at risk (43 left, 48 right) were identified. Fourty four (52.4%) of 84 EBSLNs were identified visually, before being stimulated with the probe. Additionally, 18 (21.4%) EBSLNs were identified visually, after being identified with the probe. Although 22 (26.2%) EBSLNs were identified with the probe, they were not able to be visualized. The IONM provided significant contribution to visual (p<0.05) and functional (p<0.001) identification of EBSLN. Positive EMG responses were obtained from 44 (52.4%) of 84 identified EBSLNs. Unilateral or bilateral positive EMG responses were achieved from the TA muscles in 29 (70.7%) out of bilaterally intervented 41 patients, with the stimulation of the EBSLNs. Positive EMG waveforms of TA muscles were detected in 13 (44.8%) patients bilaterally and 16 (55.2%) patients unilaterally. Conclusion: IONM is superior to the only visual identification, because IONM improves the visual and functional identification rate of the EBSLN. We suggest that the IONM should be used to diminish the risk of EBSLN injury in the superior pole dissection routinely. Although the EBSLN's main function is to innervate the cricothyroid muscle, it also contributes to the vocal cord's adductor function unilaterally or bilaterally, in two third of the patients. This innervation may be related to the vocal cord's functional and positional variabilities in the patients with RLN paralyses after thyroidectomies.
Sims TMS for laryngeal nerves.pdf
Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves in 10 normal volunteers [7 male, 3 female]. Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.
Annals of Otology, Rhinology & Laryngology, 1997
The neuroanatomy of the larynx was explored in seven dogs to assess whether there is motor innervation to the thyroarytenoid (TA) muscle from the external division of the superior laryngeal nerve (ExSLN). In 3 animals, such innervation was identified. Electrical stimulation of microelectrodes applied to the ExSLN resulted in contraction of the TA muscle, indicating that this nerve is motor in function. This was confirmed by electromyographic recordings from the TA muscle. Videolaryngostroboscopy revealed improvement in vocal fold vibration following stimulation of the ExSLN compared to without it. Previously, the TA muscle was thought to be innervated solely by the recurrent laryngeal nerve. This additional pathway from the ExSLN to the TA muscle may have important clinical implications in the treatment of neurologic laryngeal disorders such as adductor spasmodic dysphonia.
Relation of recurrent laryngeal nerve compound action potential to laryngeal biomechanics
The Laryngoscope, 1995
This study was designed to investigate the compound action potential (CAP) of the recurrent laryn-geaI nerve (RLN) and to correlate this electrophysiologic signal to laryngeal biomechanics and phonatory funetion. Four adult mongrel canines were anesthetized. The RLN was isolated and stimulated, and recording electrodes were applied. The electromyographic (EMG) electrode was placed in the thyroarytenoid (TA) muscle. The RLN CAP and the EMG of the TA muscle were recorded and eompared to the stimulation intensity, subglottie pressure (P sub)' and each other. The CAP peak-to-peak and EMG peak-to-peak amplitudes demonstrated a sigmoidal relation to stimulus intensity and a linear relation to P sub and to each other. On the basis of these findings, the RL.'T CAP appears to be a reliable physiologie measure of laryngeal function.
Head & neck, 2017
Background: The posterior cricoarytenoid muscle is the abductor muscle for the vocal cords and is innerved by the recurrent laryngeal nerve (RLN). The purpose of this study was to present our determination if the external branch of the superior laryngeal nerve (SLN) contributes to the motor innervation of the posterior cricoarytenoid muscle. Methods: We performed electromyographies (EMGs) via needle electrodes on 47 posterior cricoarytenoid muscles from 28 patients during thyroidectomy (9 lobectomies and 19 total thyroidectomies) with intraoperative neural monitoring. The RLN, vagus nerve, and external branch of the SLN were stimulated intraoperatively and the responses were evaluated by EMG. Results: Positive EMG responses were obtained from 16 (34%) of 47 posterior cricoarytenoid muscles after external branch of the SLN stimulation. The EMG of the posterior cricoarytenoid muscle was unilaterally positive in 8 of 19 patients (42%) with total thyroidectomy, and 2 of 19 patients (10.5%) were bilaterally positive. Conclusion: The external branch of the SLN contributes to the ipsilateral posterior cricoarytenoid muscle innervation in one-third of the cases. This contribution is usually unilateral, but is occasionally bilateral.
Anesthesia and Analgesia, 2005
Using phonomyography, a new monitoring technique of neuromuscular blockade (NMB), we compared NMB after mivacurium 0.1 mg/kg at the lateral cricoarytenoid muscle (LCA) with a possible external monitoring site of the larynx. In 12 patients, data were obtained at both sites using phonomyography. Anesthesia was induced with remifentanil 0.25-0.5 g · kg Ϫ1 · min Ϫ1 followed by propofol 2-3 mg/kg. A small piezo-electric microphone was positioned beside the vocal cords into the muscular process at the base of the arytenoid cartilage to record acoustic signals from the contraction of the LCA. A second microphone was positioned at an external site, lateral to the trachea, just below the thyroid notch. The recurrent laryngeal nerve was stimulated supramaximally using train-of-four (TOF) stimulation every 12 s. Onset, maximum effect, and offset of NMB were measured and compared. Peak effect, time to reach (T) 25%, 75%, and 90% of control twitch response, and TOF recovery to TOF ratios 0.5-0.8 were significantly longer at the external site. The onset time was not significantly different between the two sites. We used phonomyography with a microphone placed at the neck to evaluate the possibility to externally monitor NMB at the larynx. When compared with LCA, we found a more pronounced peak effect and longer offset of NMB. The acoustic signals recorded at this external site are unlikely to stem from laryngeal muscle contraction but are rather a result of contraction of the strap muscles of the neck.
Transmucosal Electrical Stimulation of Laryngeal Muscles
Annals of Otology, Rhinology, and Laryngology, 1989
A new technique is described that enables discrete activation of individual laryngeal muscles by electrical stimulation across overlying mucosa. In 15 dogs, we defined six distinct motor points by transmucosal stimulation at 3 mA while observing the resulting characteristic position of the arytenoid and true vocal cord. Five dogs were then paralyzed with succinylcholine in order to simulate bilateral vocal cord paralysis. Application of a 3-mA stimulus at each motor point yielded no motion of the cords, but when the current was increased to 20 mA, characteristic responses were elicited. In five other dogs, botulinum toxin was injected directly into laryngeal muscles. Stimulation was used in an attempt to quantify the degree of neuromuscular blockade. In the last group of five dogs, we simulated cricoarytenoid ar thritis by scarifying the joint. The extent and nature of the joint's impairment could be demonstrated by stimulation. Transmucosal stimulation appears promising as a clinical technique for correlating particular vocal cord movements and thresholds of activation with specific laryngeal disorders. Additionally, such a technique may be useful in clarifying how each laryngeal muscle acts upon the cricoarytenoid joint.
Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves in 10 normal volunteers [7 male, 3 female]. Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.
Journal of Voice, 2014
Shores, zAnn Arbor, {Detroit, Michigan, and ySantiago, Chile, and kBuenos Aires, Argentina Summary: In this retrospective case study, we report the apparent clinical effectiveness of neuromuscular electrical stimulation (NMES) in combination with voice therapy (VT) for rehabilitating dysphonia secondary to suspected superior laryngeal nerve (SLN) weakness in two female patients. Both patients failed or plateaued with traditional VT but had significant improvement with the addition of NMES of the cricothyroid muscle and SLN using a VitalStim unit. Stimulation was provided simultaneously with voice exercises based on musical phonatory tasks. Both acoustic analysis and endoscopic evaluation demonstrated important improvements after treatment. In the first patient, the major change was obtained within the primo passaggio region; specifically, a decrease in voice breaks was demonstrated. In the second patient, an improvement in voice quality (less breathiness) and vocal range were the most important findings. Additionally, each patient reported a significant improvement in their voice complaints. Neuromuscular laryngeal electrical stimulation in combination with vocal exercises might be a useful tool to improve voice quality in patients with SLN injury.