Aberrant branch of the superior laryngeal nerve passing through the thyroid foramen: a macroscopical study.

This is the first report providing detailed description on an aberrant branch (AB) which, arising from the superior laryngeal nerve (LN), passes through the thyroid foramen and is distributed to the mucous membrane of the larynx. The foramen was observed in 7 out of 14 Japanese cadavers examined in this study, 3 on the right, 3 on the left and one on both sides. In these 7 sides, the AB was given off from the external branch of the superior laryngeal nerve (LN) during its descent on the inferior constrictor muscle of the pharynx. In one side, however, it arose from both the external and internal branches of the superior LN. In each case, the AB, after passing through this foramen, reached the lateral aspect of the arytenoid cartilage, dividing into a superior and an inferior division. The superior one was communicated with a branch of the internal branch of the superior LN, while the inferior one was communicated with that of the inferior LN of the recurrent LN. The joined branches were distributed to the mucous membrane covering the ventricle of the larynx and the vocal fold. On the basis of the height of its distribution, it can be mentioned that the AB is situated intermediate in position between the internal branch of the superior and inferior LNs.