Surgical anatomy of structures adjacent to the thyroid apex and post-operative voice change (a review including dissection).

This paper considers the anatomy of structures contiguous to the upper pole of the thyroid gland. It also describes the findings of an anatomical dissection confined to the muscular and carotid triangles of the neck with the nerves therein innervating the cricothyroid and infrahyoid muscles. The segmental nature of the latter is described. The variable course of the cricothyroid artery with regard to the sternothyroid muscle is noted. A superficially placed artery is accompanied by branches of the ansa cervicalis; a deeply placed one is related to the external laryngeal nerve. In addition to the external laryngeal nerve there are other nerves, including branches of the ansa cervicalis, which can be damaged during operations involving the thyroid apex or adjacent structures. A comment is made about the significance of these findings with particular reference to voice change.