Voice changes after thyroidectomy are the fear and dread of the surgeon. His first thought is that he has injured either the superior laryngeal or the recurrent laryngeal nerve. If injury has occurred to these nerves, his fears are well-founded. However, recent observation has indicated that many instances of voice changes after thyroid surgery are the result of physiological reduction of circulating thyroxin rather than to operative trauma. This type of voice change is usually hoarseness which may properly be termed myxedematous hoarseness.
As is well known, both laryngeal nerves (superior and inferior) supply the sensory and the motor innervation of the larynx. The superior laryngeal nerve arises from the vagus. Both motor and sensory, this nerve divides into two branches, one external and one internal. The external branch (motor) supplies the cricothyroid muscle and serves as the tensor of the vocal cords. The internal branch (sensory) innervates the mucosa