In the case of hyperthyroidism which is the most common nerve to be damaged?

The recurrent laryngeal nerve innervates all intrinsic muscles of the larynx with exception of Cricothyroid muscle. Mechanisms of damage include complete or partial transection, traction, contusion and compromised blood supply. The consequence is true vocal fold paralysis. The SLN has 2 divisions: internal and external. The internal branch provides sensory innervation to the larynx. It enters the larynx through the thyro-hyoid membrane and, therefore, should not be at risk during thyroidectomy. The external branch provides a motor function to the crico-thyroid muscle and is at risk during thyroidectomy. This muscle is involved in elongation of the vocal folds. Trauma to the nerve results in an inability to lengthen a vocal fold and thus, an inability to create a high-pitched sound.