Laryngeal branching pattern of the inferior laryngeal nerve, before entering the larynx.

The objective of the present work was to investigate the laryngeal branching pattern of the inferior laryngeal nerve (ILN) in detail before the branches entered the larynx. In 49 specimens 96 sides were examined for this project, including 27 males and 22 female cadavers. In 7 sides (7.3%, 5 on the left and 2 on the right) the ILN passed as a single trunk into the larynx below the inferior constrictor muscle. In 82 sides (85.4%, 40 on the left and 42 on the right) two laryngeal branches originated from the nerve. The nerve divided either just before entering the larynx (58.3%, 24 on the left and 32 on the right) or 15-32 mm below the inferior constrictor muscle (27.1%, 16 on the left and 10 on the right). In 69 sides (71.8%), the anterior and/or posterior laryngeal branches subdivided into one or two sub-branches. The anterior (observed in 49 sides, 51%) and posterior laryngeal branches supplied all intrinsic laryngeal muscles except the cricothyroid muscle and the mucosa below the vocal cords, respectively, while their sub-branches reached the cricopharyngeal part of the inferior constrictor muscle, esophagus and/or the thyroid gland. In 7 sides (7.3%, 4 on the left and 3 on the right) the nerve divided into three laryngeal branches. In conclusion, the branching pattern of the nerve may be important pitfalls of the thyroidal and laryngeal surgery. Owing to this the surgeon should keep in mind the risk of extra laryngeal division of the nerve and not confuse laryngeal and extra laryngeal branches.