Basic science
Declan Costello, Guri Sandhu in Practical Laryngology, 2015
The superior laryngeal nerve arises from the inferior ganglion of the vagus nerve and contains both motor and sensory fibres. It passes downwards and forwards along the sides of the pharynx and medial to the carotid artery. The superior laryngeal nerve diverges into internal and external branches. The internal branch passes between the middle and inferior constrictor muscles, and then enters the larynx by piercing the thyrohyoid membrane with the superior laryngeal artery. In the larynx, this nerve divides into an ascending branch, which supplies the piriform sinus mucosa, and a descending branch, which supplies the supraglottic area. The external branch continues on the external surface of the larynx, beneath the sternothyroid muscle. It provides the motor innervation for the cricothyroid muscle. It occasionally provides a supply to the thyroarytenoid muscle and other intrinsic laryngeal muscles, albeit mainly proprioception. The superior laryngeal nerve receives a branch from the superior sympathetic ganglion on each side of the upper neck.
Cranial Neuropathies I, V, and VII–XII
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in 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).
Thyroid surgery
Pallavi Iyer, Herbert Chen in Thyroid and Parathyroid Disorders in Children, 2020
As described in the “Surgical technique” section, extreme care is taken to preserve the nerves within the neck during thyroid surgery. If the superior laryngeal nerve is injured, patients can experience alterations in voice pitch and occasional difficulties swallowing. If the RLN is injured on one side, patients will typically exhibit a hoarse or whisper-like voice that recovers in weeks to months in most cases. If both RLNs are injured, the patient could experience both vocal cords frozen in apposition to one another, creating an airway emergency necessitating temporary tracheostomy. In a recent high-volume, pediatric single-institution study, incidence of temporary hoarseness and permanent hoarseness was 1.9% and 0.4% respectively. Temporary hypocalcemia, reported as high as 7.9%, can also be experienced if there is stunning to the parathyroids during removal of the thyroid, with a small percentage of individuals experiencing permanent hypocalcemia. This can happen more frequently in younger patients, those with hyperthyroidism, and more extensive dissection as in lymphadenectomy procedures. In a minority of patients (1.3%), return to the operating room for hematoma evacuation is required (4). Thankfully, these complications have a very low incidence, and pediatric thyroid surgery has been shown to have excellent outcomes in the absence of long-term negative sequelae in the hands of an experienced, high-volume surgeon (5,6).
A spontaneous partially thrombosed ductal aneurysm presenting with left recurrent laryngeal nerve palsy
Published in Acta Oto-Laryngologica Case Reports, 2020
Abhilasha Goswami, Anandita Das
Vocal cord paralysis – definition and anatomy: The vocal cords, more often called the vocal folds due to its resemblance to folds of tissue, are located in a subsite of the larynx called the glottis. The glottis comprises of the true vocal cords, the anterior commissure, and the posterior commissure. Histologically, the vocal cords are composed of five layers. From superficial to deep, these layers are – 1) stratified squamous non-keratinizing epithelium, 2) superficial layer of the lamina propria (Rienke’s space), 3) intermediate layer of lamina propria, 4) deep layer of lamina propria, and 5) vocalis muscle. The movement of the vocal cords is controlled by the intrinsic muscles of the larynx. The recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx, except the cricothyroid, which is supplied by the internal division of the superior laryngeal nerve. Vocal cord paralysis is an inability to move the muscles of the vocal cords. It may be unilateral or bilateral. Paralysis of one vocal cord (unilateral vocal cord paralysis) can impair voice and sometimes swallowing. Paralysis of both vocal cords (bilateral vocal cord paralysis) can compromise the airway and breathing.
Correlation between dysphonia and dysphagia evolution in amyotrophic lateral sclerosis patients
Published in Logopedics Phoniatrics Vocology, 2021
Chiara Mezzedimi, Enza Vinci, Fabio Giannini, Serena Cocca
The ESLN (External superior laryngeal nerve) innervates the cricothyroid (CT) muscle, which contributes greatly to pitch elevation, and partially the inferior pharyngeal constrictor (IPC), an important portion of the UES [24,25]. The IPC is known to contribute (with other muscles) to both the pharyngeal clearance of the bolus and entrance of the bolus to the esophagus. Because of this function of the IPC, disturbances of the ESLN could potentially cause not only reduced pitch elevation but also reduced functionality reflected in timing or range of motion disturbances of the IPC and the UES, and thus larger amounts of pharyngeal residue after the swallow. Additionally, during both these functions—pitch elevation and swallowing—anterior and superior hyolaryngeal complex displacement is achieved through contraction of extrinsic laryngeal and suprahyoid muscles and simultaneous resistance of the cricopharyngeal muscle [24].
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
Twelve SLNs (55%) presented the branches of EBSLN and internal branch of the superior laryngeal nerve (IBSLN). All EBSLNs conducted EMG signal and two IBSLNs displayed EMG signal. In detail, both the EBSLNs and IBSLNs in two cases (one case on the left and another one on the right) obtained EMG signal and CTM twice (Table 3). The amplitude of EBSLN was higher, whereas the amplitude of IBSLN was lower but with a clear biphasic waveform (Table 3). One left SLN was presented as an extended and complex network structure, and all the branches did not elicit any EMG signal (Figure 5). In this study, Friedman type 2 or 3 was observed which is similar to humans. In detail, the EBSLN inserted into the inferior constrictor muscle. The sternothyroid–laryngeal triangle was routinely stimulated with a current of 2 mA, and then the nerve course was located by gradually reducing the stimulating current. The EMG profile of EBSLN could still be obtained by stimulating the inferior constrictor muscle with the current less than 1 mA, whereas no nerve fiber was identified and observed, and these were stratified as belonging to anatomical classification.
Related Knowledge Centers
- Cricothyroid Muscle
- Internal Carotid Artery
- Pharynx
- Sternothyroid Muscle
- Sympathetic Nervous System
- Larynx
- Vagus Nerve
- Inferior Ganglion of Vagus Nerve
- Pharyngeal Plexus of Vagus Nerve
- Inferior Pharyngeal Constrictor Muscle