Surgical resection of thyroid cancer may include lobe of one gland + lymph node dissection in the central region of the neck, or all of the gland + bilateral lymph node dissection in the neck. This procedure has the potential to damage important nerves closely adjacent to the thyroid, especially the recurrent laryngeal nerve, causing hoarseness and even breathing difficulties. This is described below.
Where is the recurrent laryngeal nerve? What does it do?
The recurrent laryngeal nerve (RLN) is located immediately behind the thyroid gland, one on each side, and is closely related to the thyroid gland.
They control vocal fold activity, regulate the position and opening and closing of the vocal folds, and maintain our airway function and articulatory function. It can be said that our ability to speak and sing properly, eat and drink (swallow), all depends on the hard work of the recurrent laryngeal nerve.
What are the signs of surgical damage to the recurrent laryngeal nerve?
Recurrent laryngeal nerve injury is a common and serious complication of thyroid surgery, with an incidence ranging from roughly 0.5% to 13%. It can be classified as temporary or permanent. Temporary injury is due to intraoperative strain, postoperative nerve edema, and hematoma compression and usually resolves within 3 months after surgery. Permanent injury is mostly due to direct injury (e.g., clamping, severing, suturing) and is often irreversible.
Injury to one side of the nerve may cause ipsilateral vocal cord paralysis, resulting in hoarseness. In some people, when one side of the nerve is damaged, the ipsilateral vocal folds are impaired and the opposite vocal folds can replace the function (medically called “compensatory”). After a few months, the hoarseness may improve. However, severe nerve damage may not be recovered for life.
If both nerves are damaged and the vocal cords cannot open on their own, it is not just hoarseness, it can cause obstruction of the airway, difficulty breathing, and even asphyxia. A tracheotomy is needed to assist with breathing.
How do doctors respond to a laryngeal return nerve injury?
The consequences of laryngeal nerve injury are serious, and doctors are very concerned about this and take some precautions and countermeasures before and during surgery.
Preoperative examination
Laryngoscopy is required to clarify preoperative vocal fold activity in patients with the following risk factors:
- Hypoacusis before surgery
- Large thyroid mass with potential for nerve compression
- Second surgery (e.g., previous partial thyroidectomy)
- Preoperative tests suggesting a nerve variant (e.g., “laryngeal nonretroflexion”, a rare congenital variant of the recurrent laryngeal nerve that travels in a different location than the normal recurrent laryngeal nerve and may be mistakenly injured)
If preoperative vocal cord movement is already compromised, some patients will experience hoarseness even if the surgery preserves the laryngeal recurrent nerve intact.
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Intraoperative monitoring and protection
Intraoperatively, the surgeon carefully dissects and protects the nerve. In these high-risk patients, a nerve detector is used to monitor the electrophysiological signals of the nerve in real time and to clarify whether the nerve function is intact.
If there is a situation where the nerve has to be damaged intraoperatively (e.g., tumor-nerve adhesions), the surgeon will try to separate the nerve, anastomose the nerve dissection, and preserve as much nerve function as possible.
What should patients and families be aware of?
Please understand, for you and your family, that medicine is not 100% accurate. No one can make an accurate prediction about whether or not there will be damage to the recurrent laryngeal nerve. With advances in medical technology, the probability of injury can be minimized, but there is still no guarantee that this complication will be completely eliminated.
As a patient, you need to cooperate with your surgeon for a detailed examination before surgery.
If there are no special circumstances that necessitate removal of the nerve as mentioned above, but the voice is hoarse postoperatively, do not be too nervous; most postoperative hoarseness is due to anesthetic intubation and postoperative transient edema of the nerve. At this point, relatives should encourage the patient to talk more to promote the edema to subside. If the symptoms of hoarseness do not improve after several months, it is necessary to see a doctor to perform a laryngoscopy to understand vocal cord movement.
In addition, if the vagus nerve is mistakenly injured by surgery, it may also cause choking and hoarseness. However, it is much less common than injury to the recurrent laryngeal nerve.
Co-written by Dr. Jiaqian Hu, Cancer Hospital, Fudan University