The recurrent laryngeal nerve sequentially branches into the posterior cricoarytenoid muscle, arytenoid muscle, lateral cricoarytenoid muscle and thyroarytenoid muscle, and each individual branch seems to be readily susceptible to localized penetrating injury. Thyroarytenoid muscle paralysis exists in theory and is referred to as partial vocal cord paralysis. Such cases are extremely rare, however.
Here we report five cases of thyroarytenoid muscle paralysis. Three cases were male and two female, and three among the five patients experienced partial vocal cord paralysis after surgery under general anesthesia. The laryngeal findings of all patients showed normal abductor and adductor actions on the vocal cords and bowing of the vocal cord on the paralyzed side. We believed that diagnosis of thyroidarytenoid muscle paralysis requires not only confirmation by laryngeal endoscopy but also by laryngeal electromyogram. Breathy hoarseness caused by a glottal gap and accommodation disorder of the voice register involving antagonism between the cricoarytenoid and thyroarytenoid muscles seemed characteristic of these cases.
2014 The Japan Society of Logopedics and Phoniatrics