What is Recurrent Laryngeal Nerve Injury?
The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve, which is one of the twelve cranial nerves in the head and neck area. The RLN is responsible for controlling most muscles in the voice box (larynx), except the cricothyroid muscle, and provides sensation to the area below the vocal cords. The RLN takes a roundabout route through the neck. The right RLN branches off around the chest level (T1-T2), loops under an artery in the chest called the right subclavian artery, and then travels back up through the neck. The left RLN starts near the aorta, a major blood vessel in your heart, then loops under the aortic arch and continues up through the neck.
The path that the RLN takes in the body is important to understand because it runs through several areas where it could potentially be damaged. Learning about how this nerve works and where it is located can help doctors prevent injury to the nerve during treatments or surgeries.
What Causes Recurrent Laryngeal Nerve Injury?
The recurrent laryngeal nerve controls your voice and its function can be impaired if it gets damaged anywhere along its path. This damage can often result from an injury, and one of the common causes is surgical procedures. A study looking at over 800 patients found that surgery was the most significant cause. These procedures could include surgeries on your chest, neck, or the base of your skull, but the most common are thyroidectomies and parathyroidectomies (surgeries to remove the thyroid or parathyroid glands).
Another frequent cause of this nerve damage is tumors. A study found that non-laryngeal cancer (cancer outside of the voice box) was responsible for nearly a quarter of all instances of one-sided vocal cord paralysis, with 80% of these being lung or mediastinum (the space in the chest between the lungs) cancers. That’s why it’s essential to check for cancer before assuming nerve damage is from an unknown cause.
Endotracheal intubation (when a tube is inserted into your windpipe to help you breathe) also results in numerous instances of nerve damage. If nerve damage is suspected after intubation, other possible causes, like arytenoid dislocation (a dislocated voice box), should also be considered.
While tumors, surgeries, and unknown causes are common reasons, rare causes can also include viral illnesses, diabetes-related nerve damage, and trauma.
A review of several studies found that surgery was the leading cause of one-sided nerve damage, accounting for 30-40% of all cases. Tumors were the second leading cause (17-32% of cases) and unknown causes contributed to about 10-27% of all cases. Endotracheal intubations were last, causing about 7-11% of cases.
A different article reviewed 2,267 cases of one-sided vocal cord paralysis. The top three causes — surgery, cancer, and unknown reasons — accounted for 36.9%, 29.7%, and 20.9% of cases respectively.
Risk Factors and Frequency for Recurrent Laryngeal Nerve Injury
The information available on injuries to the recurrent laryngeal nerve (RLN), which can cause vocal cord palsy, is not sufficient. Additional studies will help us understand this situation better. Diagnosing RLN injuries is tricky because they’re just one cause of vocal cord palsy. A study that tracked 325 patients showed that males were twice as likely to have laryngeal nerve palsy. This study also recorded an average age of 55 years among the participants.
Vocal cord paralysis, which is often a symptom of RLN injury, was found in 0.42% of new patients in another study. This evidence indicated that males were three times more likely to be affected than females. A similar age group, mostly people in their 50s and 60s, was reported in this study as well.
Signs and Symptoms of Recurrent Laryngeal Nerve Injury
Damaging the recurrent laryngeal nerve can lead to a loss of function in one vocal cord— a condition called unilateral vocal cord paralysis. Individuals suffering from this might notice a sudden change in their voice, including hoarseness, altered pitch, or might sound like they’re having difficulty with their breathing. If both the left and right nerves are affected resulting in bilateral vocal cord paralysis, symptoms could be more serious. These could include significant issues with breathing and swallowing.
Recent surgeries involving the head or neck, or recent instances of being fitted with a breathing tube, could be a hint that the recurrent laryngeal nerve might have been injured. Additionally, signs indicative of cancer, such as severe and long-lasting cough, inexplicable weight loss, history of tobacco or alcohol use, or difficulty swallowing, should be explored. Less usual causes can also be a recent viral sickness or an injury to the neck that results in damage to the recurrent laryngeal nerve.
Physical examination of the head and neck might reveal swollen lymph nodes, which could be due to cancer. An examination of the thyroid gland might show lumps or other irregularities, which warrants a more detailed exploration for possible cancer. If the breath sounds are decreased on one side of the upper area of the lung, a tumor in the top of the lung, also called a Pancoast tumor, may be suspected. In such a scenario,
clinical signs of certain conditions, such as Horner syndrome, thoracic outlet syndrome, or superior vena cava syndrome, may also be observed.
Testing for Recurrent Laryngeal Nerve Injury
Your doctor will start by asking about your symptoms and doing a physical exam if they suspect an injury to your recurrent laryngeal nerve (RLN), a nerve that controls your voice box. This nerve starts at the base of the skull and goes down to the chest, meaning any problems could be coming from different parts of your body. The doctor might do chest x-rays if they think the issue may be related to your lung.
In most cases, a CT scan is usually done to view the entire length of the RLN and identify any issues. A CT scan might also show signs of potential vocal cord paralysis. However, if you have symptoms of vocal cord paralysis, the doctor typically does a direct laryngoscopy before having a CT scan done. A direct laryngoscopy is done with a flexible tube that allows the doctor to see within your throat and evaluate the movement of your vocal folds. This procedure has been found very reliable when examining vocal fold motion.
In addition to the traditional methods, some other tools might be used to evaluate the vibrations of your vocal folds. One such tool is a Strobolaryngoscopy, a type of examination to look at how the vocal cords vibrate during speech.
Another way to evaluate RLN injury is through laryngeal ultrasonography, a newer technique that uses sound waves to create an image of the voice box. A study showed that this method was 83.3% effective at identifying vocal cord paralysis and 97.2% effective at ruling out vocal cord paralysis when it was not present, compared to laryngoscopy, which is the current ideal method or “gold standard” for diagnosing vocal cord paralysis.
Treatment Options for Recurrent Laryngeal Nerve Injury
When someone experiences injury to the recurrent laryngeal nerve, it can affect their voice. The primary treatment options to correct this include speech therapy or surgery. The treatment chosen usually depends on the severity of the nerve injury and how the disease has progressed.
In cases where the injury is not too severe and the nerve hasn’t been completely severed or separated, it can often be managed by monitoring for about six months, during which the patient may attend voice therapy as required. If the nerve is separated during a surgery, a procedure called end-to-end anastomosis is performed to repair the nerve.
If after a period of non-surgical treatment, improvements aren’t realized, techniques to move the affected vocal cord closer to the unaffected cord (vocal fold medialization) can be used. This helps to improve contact between the cords for better voice production. Procedures to achieve vocal fold medialization can include medialization thyroplasties, injection laryngoplasty, arytenoid adduction, and laryngeal reinnervation (nerve regeneration).
Medialization thyroplasty type 1 involves making an external incision to place an implant that permanently moves the affected vocal cord closer to the middle of the voice box. This procedure is generally safe and has a lower serious complication rate than an outpatient thyroidectomy (surgery to remove all or part of the thyroid gland).
Injection laryngoplasty is another procedure where a material is injected into the affected vocal cord. This fills and expands the cord, moving it towards the middle. The materials used for injection can vary and can include carboxymethylcellulose, hyaluronic acid derivatives, collagen derivatives, or autologous fat/fascia; however, there is no definitive advantage or disadvantage associated with using any specific material.
Arytenoid adduction is another surgical technique, which involves pulling the affected vocal cord towards the middle by placing a permanent suture through the muscular part of a cartilage in the voice box called the arytenoid cartilage. This procedure is commonly used along with other corrective procedures for treating vocal cord paralysis secondary to recurrent laryngeal nerve injury.
What else can Recurrent Laryngeal Nerve Injury be?
Vocal cord paralysis can be due to several causes, specifically damage to the recurrent laryngeal nerve. Some possible causes include:
- Iatrogenic (caused by medical treatment or procedure) – This could happen during the insertion of a breathing tube or during surgical procedures on the skull base, neck, or chest.
- Malignancy (cancer) – Particularly of the skull base, neck, or chest.
- Trauma – This includes injuries to the neck, chest, larynx (voice box).
- Neurological – Conditions such as stroke (specifically a type called lateral medullary syndrome), bulbar palsies (nerve damage affecting the face and mouth), and diseases causing a breakdown of the protective covering of nerve fibers.
- Idiopathic – This is a term used when no specific cause can be identified.
What to expect with Recurrent Laryngeal Nerve Injury
Injuries to the recurrent laryngeal nerve, which is responsible for supplying nerves to the voice box, can be either temporary or permanent. These injuries can have different outcomes and recovery timelines, which can depend on many things such as how the injury occurred and how severe it is. Nerve injuries can also either fully heal or partially heal, which shows how complex they can be.
There are different grades of nerve injuries. For instance, neuropraxia is a mild type of injury where the nerve itself isn’t damaged, only the myelin sheath – the protective layer around the nerve. With this type of injury, the nerve usually recovers within 6 to 8 weeks. Axonotmesis, on the other hand, involves damage to the nerve’s axon, which are like long wires that carry electrical impulses. The severity of axonotmesis and its prognosis can vary.
In a study looking at patients who had their thyroid removed because of cancer, 9.5% of patients experienced injuries to the recurrent laryngeal nerve, which caused weakness in their vocal cords. Unfortunately for 22% of these patients, the weakness became permanent, requiring further treatments.
The prognosis or expected outcome for patients with recurrent laryngeal nerve injuries is a complex issue, needing a tailor-made approach for each individual patient.
Possible Complications When Diagnosed with Recurrent Laryngeal Nerve Injury
One of the severe complications following surgery is breathing difficulties due to damage to both sides of the recurrent laryngeal nerve in the throat. However, this is not a common occurrence – it’s more usual to have damage on only one side. Breathing in food or drink and developing aspiration pneumonia is a major concern for vulnerable individuals. Also, if only one side of the nerve is damaged, it can still cause substantial issues like swallowing difficulties and voice changes. These complications can greatly impact a person’s overall quality of life, especially for those whose professions rely heavily on their vocal cord usage, like public speakers or singers.
Common Complications:
- Difficulties in breathing due to bilateral recurrent laryngeal nerve injury
- Unilateral recurrent laryngeal nerve injury
- Aspiration pneumonia
- Swallowing difficulties
- Voice changes
- Potential impact on quality of life for professions relying on vocal cord usage
Preventing Recurrent Laryngeal Nerve Injury
If you have a recurrent laryngeal nerve injury, it’s important to understand why this might have happened. Sometimes this can hit after surgery, but if during your operation the nerve wasn’t cut, it’s likely the issue you’re experiencing with your vocal cords is temporary. However, if you’re also having signs of something more serious, like cancer, it’s very important that you continue to have regular checks and follow-ups with your doctor.
In general, if you’re not showing signs of a serious health problem like cancer or physical trauma, you can usually take comfort in knowing that this kind of nerve injury is often from an unexplained, or ‘idiopathic’, cause and it’s typically not something that will be with you permanently. However, as always, it’s important that you still have thorough medical tests to make sure nothing else is causing your nerve injury.