The thyroid gland is a disease-prone organ and many thyroid disorders such as thyroid cancer and cysts require surgery, at which point the surgeon will often send the patient to the ENT for a laryngoscopy to clarify the condition of the vocal cords. Sometimes, patients who have undergone thyroid surgery develop hoarseness, why is this? This is probably caused by injury to the recurrent laryngeal nerve, the nerve that innervates our larynx. The recurrent laryngeal nerve is on the left and right side, and if various factors cause pressure on the recurrent laryngeal nerve, severing and other factors, paralysis of the recurrent laryngeal nerve will occur, so that the intralaryngeal muscle innervated by the recurrent laryngeal nerve is paralyzed and vocal cord movement is impaired, along with choking and choking caused by laryngeal sensory paralysis. The left side of the laryngeal nerve is about twice as common as the right side because of the long path between the left vagus nerve and the recurrent laryngeal nerve. According to the nature of the cause of laryngeal nerve paralysis: (1) trauma: skull base fracture, lateral skull base surgery, neck trauma and surgery, thyroid surgery, thoracic mediastinal surgery, anterior cervical spine surgery and other injuries to the vagus nerve or laryngeal nerve can cause laryngeal paralysis. (2) Tumors and other occupying lesions: compression of the vagus nerve by tumors of the pontocerebellar angle, infiltration of the skull base by nasopharyngeal carcinoma or compression of the vagus nerve at the jugular foramen can cause laryngeal paralysis; metastatic tumors of the neck, thyroid tumors, Hodgkin’s disease, carotid aneurysms, etc. can compress the vagus nerve and cause laryngeal paralysis; aortic aneurysms, mediastinal tumors, lung cancer, tuberculosis, esophageal cancer, pericarditis, esophageal achalasia, etc. can compress the thoracic segment and cause laryngeal paralysis. The laryngeal paralysis can occur due to compression of the recurrent laryngeal nerve. (3) Inflammation: Infectious diseases such as influenza, laryngeal diphtheria, lead and other chemical poisoning, acute rheumatism, measles, syphilis, etc. can cause laryngeal paralysis due to perineuritis of the laryngeal nerve. Central factors leading to laryngeal nerve paralysis are less common. In thyroid surgery, the incidence of injury to the recurrent laryngeal nerve is 1.2% to 2.7%, mainly caused by careless handling of the inferior thyroid artery or removal of the gland. Dissection and suturing are permanent injuries that can only be avoided by careful intraoperative manipulation. Extrusion, traction and hematoma compression are temporary injuries that can generally be recovered within 3 to 6 months after physical therapy. If the anterior branch of the recurrent laryngeal nerve is injured, the ipsilateral vocal folds will be abducted; if the posterior branch is injured, the vocal folds will be adducted. The treatment principles of laryngeal nerve palsy: ① first find and treat the cause of the disease as much as possible; ② vocal fold palsy should be observed for at least 6 months before mechanical permanent treatment, and surgery should be performed only when there is no hope of restoring vocal fold function; ③ the choice of surgery should be based on the cause, type, severity, special needs of the patient, and general condition; ④ for trauma (4) For patients with severe laryngeal nerve injury, including surgical injury and mechanical compression, patients with no hope of restoring vocal cord function should undergo laryngeal nerve exploration and corresponding nerve repair treatment as soon as possible; (5) Symptoms such as laryngeal obstruction, aspiration and choking caused by vocal cord paralysis should be treated promptly.