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Thyroidectomy
Published in Mark Davenport, James D. Geiger, Nigel J. Hall, Steven S. Rothenberg, Operative Pediatric Surgery, 2020
The superior parathyroid gland is usually found lateral to the recurrent laryngeal nerve at the level of the cricoid cartilage. The inferior parathyroid glands most often are located anterior to the recurrent laryngeal nerve and caudal to the intersection of the recurrent laryngeal nerve and the inferior thyroid artery. The recurrent laryngeal nerve has a slightly different course on the right side compared to the left. On both sides the recurrent laryngeal nerves enter the larynx posteromedially in the cricothyroid muscle just superior to the cricoid cartilage. The recurrent laryngeal nerve wraps around the innominate artery on the right and enters the larynx from a more lateral to medial direction than does the left recurrent laryngeal nerve, which wraps around the aortic arch deeper in the chest and runs more parallel in the tracheoesophageal groove.
Cranial Neuropathies I, V, and VII–XII
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
The motor fibers of the vagus nerve arise from the nucleus ambiguus, which receives bilateral supranuclear innervation. These fibers supply all striated muscles of the larynx and pharynx, except the stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by V3 division of CN V).2 Three motor branches arise from the vagus nerve: the pharyngeal nerve, the superior laryngeal nerve, and the recurrent laryngeal nerve. The pharyngeal nerve travels between the internal and external carotid arteries, forms the pharyngeal plexus with the glossopharyngeal nerve, and innervates muscles of the pharynx and palate. The superior laryngeal nerve takes off distal to the pharyngeal branch and descends lateral to the pharynx. The external branch of the superior laryngeal nerve supplies the cricothyroid muscle. The third motor branch arising from the vagus nerve is the recurrent laryngeal nerve. The right and left recurrent laryngeal nerves follow different courses: the right recurrent laryngeal nerve descends anterior to the right subclavian artery and turns posteriorly under the artery to ascend in the tracheoesophageal sulcus, whereas the nerve on the left turns posteriorly around the aortic arch and ascends in the same sulcus on the left. Both recurrent branches then enter the larynx and supply all intrinsic muscles of the larynx except the cricothyroid muscle (supplied by the external branch of the superior laryngeal nerve).
Anatomy overview
Published in Stephanie Martin, Working with Voice Disorders, 2020
The larynx is innervated by branches of the vague nerve on each side. Sensory innervations to the glottis and laryngeal vestibule is by the internal branch of the superior laryngeal nerve. The external branch of the superior laryngeal nerve innervates the cricothyroid muscles. There are eight extrinsic muscles, four of which lie above the level of the hyoid – the suprahyoid muscles, which act principally to elevate the larynx and support the hyoid bone. Four lie below the hyoid – the infrahyoid muscles, which act as laryngeal depressors. The latter are particularly important in lengthening the vocal tract, which has a significant effect on vocal resonance. Detailed descriptions of the extrinsic laryngeal muscles can be found in a number of texts, but for the purposes of this chapter an outline of the muscles, their function and innervation are given in Table 1.4.
Anatomical and functional identification of the external branch of the superior laryngeal nerve: classification based on morphology and electrophysiological monitoring
Published in Acta Chirurgica Belgica, 2022
The external branch of the superior laryngeal nerve (EBSLN) is the motor innervation of the cricothyroid muscle (CTM) that adjusts the tension and length of the vocal cords (VC). Previously, EBSLN was qualified as a ‘neglected nerve’ in thyroid surgery since its palsy had been reported to possibly cause only subtle changes because injury to the recurrent laryngeal nerve (RLN) is more clinically significant compared to those affecting the EBSLNs. The actual rate of vocal impairment due to EBSLN injury is unclear since the changes to the everyday speaking voice can be minimal, and the laryngeal findings are usually occult and controversial [1–3]. On the other hand, appropriate CTM contraction and proper tension of the VCs provide a voice quality that holds paramount importance for voice professionals. Complication-free thyroid surgery primarily depends on the intact function of laryngeal nerves and motor innervations of the laryngeal musculature [4–7].
Investigation on EMG Profiles of the Superior Laryngeal Nerve in a In Vivo Porcine Model
Published in Journal of Investigative Surgery, 2020
Yishen Zhao, Changlin Li, Xiaoli Liu, Le Zhou, Daqi Zhang, Jingwei Xin, Tie Wang, Shijie Li, Hui Sun, Gianlorenzo Dionigi
The management of the external branch of the superior laryngeal nerve (EBSLN) during the dissection of upper thyroid pole is elaborate and surgeons evade the exposure of EBSLN [1–5]. Intraoperative neural monitoring (IONM) has been proposed to assist the identification of EBSLN [5–9]. The prevalence of EBSLN injury is between 0 and 40% [10]. The lesion from EBSLN ends in the dysfunction of cricothyroid muscle (CTM), modified voice frequency, timbre, performance (high-pitched intonations), reduction in the voice quality prolOngation and extra effort to speak, particularly significant in women and those using their voice professionally, such as announcers, advertising speakers, actors, secretaries, radio speakers, teachers, voice talents and journalists [3–8]. In the literature, the studies dealing with the quantitative data analysis on EBSLN IONM are very limited [3–8]. To the best of our knowledge, there are no studies which focus on investigating the dynamic response of EBSLN to the increasing stimulation [1–24]. Thus, in this study, we developed an in vivo porcine model to define and match the EMG profiles of EBSLN and to examine an ideal electrical intensity for definite stimulation of EBSLN.
Singing voice: acoustic parameters after vocal warm-up and cool-down
Published in Logopedics Phoniatrics Vocology, 2020
Chiara Mezzedimi, Maria Carla Spinosi, Tommaso Massaro, Fabio Ferretti, Jacopo Cambi
The F0 decrease after cool-down allows us to make a few considerations about the immediate effect of this practice. Physiologically, this decrease is due to a reduction in the vocal fold length and tension and an augmentation of the vibrating mass. This could be due to cricothyroid muscle release and to a greater recruitment of the thyroarytenoid muscles fibers, which is essential for the production of low frequency sounds. The vocal cool-down session favored the transition from a post-performance to a baseline condition, closer to the spoken voice, preventing post-performance muscle stress. This confirms the importance of using specific vocal cool-down techniques, as highlighted by Onofre et al. [19] study, where 30 min of voice rest did not favor the F0 decrease. These findings hint that this practice should be encouraged and not neglected or bypassed, as it commonly is since cool-down is sometimes even considered part of the "natural" physiology by a few singing teachers [27].