Overview The actual incidence of supraglottic nerve injury in thyroid surgery is close to that of the recurrent laryngeal nerve injury. The rate of supraglottic nerve injury in thyroid surgery has been reported in the literature to be approximately 0.3% to 14%, and is often overlooked by surgeons because of its mild symptoms and signs. Injury to the external branch of the superior laryngeal nerve can cause paralysis of the cricothyroid muscle, resulting in relaxation of the vocal cords and lowering of voice pitch; injury to the internal branch of the superior laryngeal nerve can cause loss of sensation in the laryngeal mucosa, which can cause choking and coughing when eating, especially when drinking water. Due to the different anatomical locations of the internal and external branches of the superior laryngeal nerve, the external branch is mostly injured during thyroid surgery. Analysis of causes 1. Intraoperative bleeding from the superior thyroid vessels and blind clamping of tissue to stop bleeding are the most common causes of supraglottic nerve injury. 2. Ligating too high when dealing with the superior thyroid pole, ligating the supraglottic vessels and the supraglottic nerve together. 3, Blunt nerve injury caused by excessive stretching of the upper pole of the thyroid gland. 4.The supraglottis is treated with ultrasonic knife and the local temperature is too high to burn the supraglottic nerve. 5.The location of the supraglottic nerve has a large variability and may also cause changes in the anatomical relationship of the nerve due to mass extrusion. 6.Severe adhesions with surrounding tissues in case of tumor or inflammation make dissection difficult. Preventive measures Be familiar with and understand the anatomical relationship between the supraglottic nerve and the supraglottic vessels. The superior thyroid artery should be separated and ligated close to the superior pole of the gland, away from the lateral plate of the thyroid cartilage, pushing away the lax tissue of the superior vessels medially and laterally, separating and ligating the artery close to the superior pole between the true and false envelope of the thyroid gland, and avoiding large ligatures. Intraoperatively, the gland is dissected closely without routine exposure of the supraglottic nerve. Solution steps and techniques 1. After the external branch of the superior laryngeal nerve leaves the superior thyroid vascular sheath, it enters the larynx 3.5 to 4 cm from the superior pole of the thyroid gland. When separating and ligating the superior thyroid vessels, care should be taken to ligate 1.5 to 2 cm distal to the vessels, which helps to avoid damage to the nerve. When the gland is large and the upper pole is too high, the branches of the upper vessels can be ligated one by one close to the gland, without reluctantly dealing with the upper thyroid vessel trunk. 3. In case of carcinoma of the upper pole of the thyroid, the external branches of the superior laryngeal nerve should be routinely exposed and protected. 4.When clearing the lymph nodes near the superior laryngeal artery during cervical dissection, special attention should be paid to the main trunk and branches of the superior laryngeal nerve. 5.Intraoperative application of electromyography can detect the contraction of cricothyroid muscle and changes of electromyography in time, which can help to avoid injury. Post-treatment observation points If the supraglottic nerve is found to be dissociated intraoperatively, it should be nerve anastomosis; if the supraglottic nerve is damaged by intraoperative clamping and suturing, but not dissociated, neurotrophic drugs are given postoperatively, and the function can be restored after 3-6 months.