Damage to the recurrent laryngeal nerve is most commonly caused by surgery on the thyroid gland, when the inferior thyroid artery is ligated, resulting in localized nerve damage. Unilateral damage may result in hoarseness of speech, while bilateral damage may result in dyspnea or even asphyxia. In other cases, malignant tumors with metastases in the neck or upper mediastinal lymph nodes may easily involve or compress the recurrent laryngeal nerve, which may cause hoarseness, coughing up sputum, and in severe cases, intrapulmonary infection. In patients with malignant tumors, local metastases can be controlled by radiation therapy.