Relative movements of the thyroid and cricoid cartilages assessed by neural stimulation in dogs

The literature abounds with contradictory answers to the question whether it is the cricoid or the thyroid cartilage that moves during changes in the fundamental frequency of the voice. If we assume that the cricoid is less resistant to movement than the thyroid, it is the cricoid that should be the moving member at the cricothyroid joints. This hypothesis was tested and confirmed in 15 dogs by stimulating the superior and recurrent laryngeal nerves, which supply the cricothyroid and thyroarytenoid muscles respectively. When the superior laryngeal nerve was stimulated, the cricoid arch always moved upward. It always moved backward, i.e., caudad, when the recurrent nerve was stimulated. At no time did movement of the thyroid cartilage result from stimulation of the laryngeal nerves.