External laryngeal nerve landmarks revisited.

BACKGROUND: Because external laryngeal nerve (ELN) iatrogenic damage is frequent during neck surgery, its precise localization has been highly recommended. This study analyzes the different surgical landmarks previously proposed and the anatomy of the collateral and terminal branches of the ELN. METHODS: The necks of 157 (77 men and 80 women) human adult embalmed cadavers were examined. The ELN origin, length, and relationship to different landmarks were recorded and results statistically compared with those previously reported. RESULTS: The ELN is located deep to the ascending pharyngeal vein in 100% of patients. In most patients, it crosses the carotid axis at the thyroid artery origin level (47% of patients), passes medial to it (89% of patients), and shows an intramuscular trajectory through the inferior constrictor of the pharynx (80% of patients). CONCLUSION: The ELN position, in relation to classical landmarks, is highly variable. The most reliable relationships are those with the ascending pharyngeal vein or with the superior thyroid artery.

Understanding the anatomy of the larynx from the era of Gimbernat to the present day moving towards laryngeal transplantation

Knowledge of the gross anatomy of the larynx in Spain throughout the period when Gimbernat was working as a surgeon and anatomist was considerable; very much comparable to our present understanding. However, the lack of aseptic surgical technique, anaesthesia, and antibiotics limited the ability to undertake complex surgery. Nevertheless, it was during that period when for first time it became possible to diagnose some laryngeal pathologies, thanks to the invention, by a Spanishsinger, Manuel Garcia (1805-1906), of a primitive laryngoscope that made it possible to see the laryngeal interior. Only in 1873 was the first major surgery of the larynx was reported when Billroth undertook the first laryngectomy to treat surgically laryngeal carcinoma. It was more than a hundred years later, before the first laryngeal transplantation was attempted by Strome and his team (1998), and though initially meeting with some success, that transplanted larynx had to be removed 14 years later. Based on our current understanding of laryngeal anatomy and surgical technique, we argue that there are four factors that must be addressed if satisfactory transplantation of the larynx to be achieved: 1) psycho-social and ethicolegal aspects; 2) tissue viability vs. rejection; 3) restoration of a vascular, and 4) selective reinnervation of the larynx has to be achieved. The three first factors are being addressed, however, the selective reinnervation remains challenging because the nerve supply of the larynx is now known to be much more complex than many accounts imply. This is because: 1) each laryngeal muscle may receive a variable number of nerve branches; 2) there are multiple connections between the different laryngeal nerves; 3) many laryngeal nerves and connections are mixed conveying both motor and sensory fibres; and 4) the laryngeal muscles may receive a dual nerve supply, from both the recurrent laryngeal and superior laryngeal nerves (AU)

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Are the interarytenoid muscles supplied by branches of both the recurrent and superior laryngeal nerves?

OBJECTIVES/HYPOTHESIS: It has been generally accepted that the branches of the internal branch of the superior laryngeal nerve to the interarytenoid muscle are exclusively sensory. However, some experimental studies have suggested that these branches may contain motor axons, and therefore that the interarytenoid muscle is supplied by both the superior and recurrent laryngeal nerves. The aim of this work was to determine whether motor axons to the interarytenoid muscles are present in both laryngeal nerves. STUDY DESIGN: Basic research. METHODS: Twelve human internal branches of the superior laryngeal nerve were dissected, and its branches to the interarytenoid muscle were removed and processed for choline-acetyltransferase immunohistochemistry, a method not used previously in studying the nerve fiber composition of the laryngeal nerves. RESULTS: The internal branch of the superior laryngeal nerve divided into two to five branches to the interarytenoid muscle. All branches contained motor axons, with the proportion of motor axons varying from 6% to 31%. CONCLUSION: The present study confirms that the internal branch of the superior laryngeal nerve provides a motor innervation to the interarytenoid muscles. LEVEL OF EVIDENCE: N/A. Laryngoscope, 126:1117-1122, 2016.