Unilateral Vocal Fold Paralysis

What is Unilateral Vocal Fold Paralysis?

Vocal fold immobility is a term used to describe abnormal movement of the true vocal folds, which are the parts of the body that produce sound for speech. This abnormality can either be partial (paretic), where the movement is decreased, or full (paralytic), which means there’s no movement at all. In some cases, this condition can affect one side (unilateral) or both sides (bilateral) of the vocal folds. It is more common to see unilateral vocal fold paralysis.

The vocal folds and the surrounding muscles in your throat are controlled by nerves that originate from a part of the brain known as the nucleus ambiguus, which is in the brainstem medulla. These nerves are called the vagus nerve, which is the 10th cranial nerve. It starts from the brainstem, goes down past the skull base, and progresses into the neck. The vagus nerve has 3 main branches that it sends out: the pharyngeal branch, superior laryngeal nerve (SLN), and the recurrent laryngeal nerve (RLN). The SLN is responsible for the sensation in the upper part of our vocal folds known as the superior glottic aspect and the movement of a muscle in the throat known as the cricothyroid muscle.

The RLN goes further down into the neck and chest area, loops around major blood vessels like the subclavian artery on the right and aortic arch on the left. It then goes back up into the neck along the tracheoesophageal groove, a groove between the windpipe and food pipe. It finally enters the vocal folds area from the back, near a joint called the cricothyroid joint. However, for a small percentage of people, the RLN directly controls the vocal folds without going into the chest area. The RLN gives us sensation in the glottis and subglottis – the lower parts of the vocal folds, and controls most of the throat muscles including the posterior cricoarytenoid, interarytenoid, lateral cricoarytenoid, and thyroarytenoid muscles. Unilateral vocal fold paralysis could be due to problems anywhere along the pathway of the RLN. Any injury to the SLN is usually not a significant factor in unilateral vocal fold paralysis.

What Causes Unilateral Vocal Fold Paralysis?

What causes Unilateral Vocal Fold Paralysis (UVFP), a condition that affects one side of your vocal chords, can differ depending on where you live and the time period. From 1985 to 1995 in North America, the main cause of UVFP was cancer. However, from 1996 to 2005, more cases were tied to accidental damage during surgery, with 37% of the instances being attributed to this. And 66% of these injuries were from surgeries not related to the thyroid, surpassing thyroid surgeries as the most common cause of injury. However, a big study conducted in Italy found thyroid surgeries to be the major cause of UVFP, followed by unknown causes and chest surgeries.

Certain types of cancer such as those of the lung and larynx are commonly associated with UVFP. Cancers of the thyroid and central nervous system are less common causes. A study from Stanford University found that among 1,019 cases of UVFP from 1970-1991, tumors were the main cause in 35.5% of the cases. Out of these, 54.8% had lung cancer.

Damage to the vocal chords is also often blamed on thyroid surgery. When the structure of the laryngeal nerve (a nerve in the vocal chords) is not typical, or when the surgery is repeated or involves thyroid cancer, the chances of UVFP happening after surgery increase. To lessen the risk of nerve damage, surgeons often use nerve stimulators but their usefulness hasn’t been clinically proven. However, continuous monitoring of the nerve during surgery has been linked with a lower risk of muscle weakness and paralysis compared to intermittent nerve stimulation.

Surgeries that pose a high risk to the laryngeal nerve include those involving the neck’s cervical spine, esophagus, and chest surgeries. Any surgery that involves inserting a tube into the trachea (the main airway) can cause UVFP, either through pressure from the tube or physical damage to the arytenoids, a part of the larynx.

Problems in the brain such as stroke, brain stem or skull base tumors, and peripheral nerve disorders should also be considered when diagnosing UVFP. Working out if UVFP is due to a problem in the nervous system is unusual, with such cases making up less than 5% of the total. But some studies have shown that up to 20% of the patients with UVFP of unknown cause were later found to have a primary neurologic disorder.

Physical causes like dislocation of the cricoarytenoid joint, a part of your larynx, should also be taken into account. This is especially important in recent cases of trauma to the voice box or intubation – the process where a tube is inserted into the windpipe through the mouth or nose. Were you recently involved in a blunt or sharp neck injury? It should then strongly suggest this might be the cause. However, the chances of UVFP happening after intubation is extremely low, often quoted as 0.1% or less.

When doctors simply don’t know what caused the UVFP, it’s referred to as idiopathic UVFP. Some believe it might be due to a virus. But before it can be called idiopathic, doctors have to rule out other more serious issues. Overall, 29% to 67% of UVFP cases are considered idiopathic, making it one of the most common categories of causes.

Risk Factors and Frequency for Unilateral Vocal Fold Paralysis

One American study found that idiopathic Unilateral Vocal Fold Paralysis (UVFP), a condition where one side of the voice box doesn’t move correctly, occurs in about 1.04 people out of 100,000 each year. Interestingly, this study discovered that UVFP cases caused by nerve problems didn’t differ significantly in age, gender, or duration of symptoms in comparison to UVFP cases not caused by nerve problems. Nonetheless, individuals with nerve-related UVFP were mostly likely to have a history of cancer or thyroid disease.

In other studies focusing on preoperative UVFP (UVFP diagnosed before surgery), the following information was found:

• Approximately 1.3% of patients about to undergo thyroid surgery had preoperative UVFP.
• 76% of these patients were eventually diagnosed with a thyroid malignancy (cancer).
• However, UVFP is not exclusively linked to thyroid cancer but it should be taken as a concerning sign.
• The chance of using developing UVFP after thyroid surgery varies-nearly half percent to 9.5%.

In addition, researchers have found that UVFP sometimes occurs in patients who had different types of surgeries:

• 1.2% of lung cancer surgery patients.
• Between 0% and 59% of esophageal cancer surgery patients.
• 25% of cardiothoracic surgery patients (surgery on the heart and lungs).
• Between 2.3% and 24.2% of cervical spine surgery patients.

Further, the rate of UVFP occurring after accidents that caused neck injuries is not widely known. It’s more common with neck injuries from blunt force trauma and more frequently leads to both sides of the voice box being paralyzed.

Signs and Symptoms of Unilateral Vocal Fold Paralysis

Unilateral vocal fold paralysis, or UVFP, is a condition that affects the voice. The primary symptom is hoarseness, but other symptoms can include coughing, a sensation of a lump in the throat, trouble breathing and swallowing, and choking. Depending on the exact location of the paralysis, the severity of voice changes can vary. In some cases, the patient might also experience difficulties with swallowing, which can lead to more serious issues such as recurrent pneumonia.

It’s important to gather as much information as possible, including when the symptoms began, what other physical signs are present, and whether there is a history of related health problems in the individual or their family. Circumstances such as a history of smoking or drinking, or exposure to harmful substances, could point to a potential cancerous cause.

A detailed physical examination, including a thorough check of the head, neck, and chest area, should be performed. Examining the vocal folds with either a mirror examination or flexible laryngoscopy can provide insight into the condition. Using stroboscopy, a technique that uses a flashing light to examine the vocal cords, can also be helpful. The diagnosis and treatment plan can greatly depend on the precise location of the problematic vocal fold and its ability to move.

Testing for Unilateral Vocal Fold Paralysis

If you recently underwent thyroid surgery or neck surgery and are now experiencing an issue known as Unilateral Vocal Fold Paralysis (UVFP), your surgeon may not have to perform additional tests. However, they must determine whether the nerve related to this issue was unharmed at the end of the procedure.

But in cases where UVFP’s cause is unknown, your doctor will need to check the path of the nerve in question, called the Recurrent Laryngeal Nerve (RLN). This nerve starts at the base of the skull and then travels down to the neck and chest. Imaging techniques, like a CT scan or an MRI, can be used to visualize the RLN and check for issues. The best technique will depend on several factors, including your symptoms and your doctor’s preference.

In some cases, if you have symptoms like weakness affecting the roof of your mouth, imaging of the skull and the nervous system might be needed. This could indicate an injury high up in the RLN pathway.

Another test, known as Laryngeal Electromyography (LEMG), might also be helpful. LEMG might be used to rule out a specific cause of UVFP, like dislocation of a part of the voice box called the Cricoarytenoid (CA) Joint. If the CA Joint is dislocated, LEMG results should look normal, because the muscles and nerves will still be functioning.

LEMG is often used to track how a paralyzed vocal fold is recovering or how it’s responding to treatment to restore nerve function. It’s most informative if done 1 to 6 months after the initial injury or start of the paralysis.

During LEMG, your doctor will look for several key findings: normal patterns suggesting the nerve and muscle connection is fine, patterns called ‘fibrillation potentials’ pointing to nerve damage in the muscle, or what are called ‘polyphasic action potentials’, which indicate that the muscle is relearning how to work after nerve damage. These results guide treatment decisions for your unique situation.

Treatment Options for Unilateral Vocal Fold Paralysis

Treatment for Unilateral Vocal Fold Palsy (UVFP), a condition where one side of your vocal cords is unable to move, often depends on the individual situation of each patient. The focus usually includes addressing the underlying cause, preventing any food or liquid from entering the airways (aspiration), and improving speech (dysphonia).

Some kinds of UVFP occur from unknown causes, and are thought to be typically the result of a viral or infectious harm, just like in cases of facial paralysis or hearing loss. Some people with this kind of UVFP may not fully regain the ability to move their vocal cords at the same speed, even if speech therapy can help improve their voice before complete recovery. Typically, if a patient doesn’t have any aspiration or any dangerous condition related to UVFP, waiting and observing the condition for 12 months with speech therapy can help. In some cases, this method can even help regain regular vocal cord movement without having to resort to more invasive treatments.

For some patients, surgical procedures may be the best course of action. These procedures can include temporary or permanent changes to vocal folds (the parts of your vocal cords that vibrate to make sound). These changes aim to move the paralyzed vocal fold towards the middle of your throat. This process allows the other healthy vocal fold to effectively close your voice box when swallowing or speaking which helps prevent aspiration and improves your voice.

Patients with UVFP who also experience aspiration may require more immediate intervention, such as injectable treatments to protect their airway and keep them from developing pneumonia. These treatments can also help patients who don’t experience aspiration but have a noticeable change in their voice. For example, a temporary injection can improve the voice’s quality. There are various types of substances used for injections like Hyaluronic acid, which is preferred when a spontaneous recovery is expected.

Patients with UVFP that doesn’t improve after 12 months may undergo permanent changes to the vocal folds. These may include injections with substances like your own body fat. Over the years, various materials have been used for these injections, like Teflon and gel foam, but these have been associated with certain side effects, so their usage is reduced today. Hyaluronic acid is oftentimes the preferred substance for injection due to its similarity to our natural body tissue. These injections can be precisely administered and generally last between 4 to 12 months, depending on the brand used. In some cases, it’s possible to use body materials, like fat or fascia; nonetheless, the results are variable, and these options may not be used as much.

The injections can be performed in a hospital or an office setting, and can be done with the patient awake or under general anesthesia. The choice between these depends on several factors like the patient’s health and risk associated with undergoing anesthesia. In-office procedures also allow immediate feedback on voice improvement. However, there might be more difficulty in placing the injection accurately compared to procedures under anesthesia.

There are also more permanent surgical solutions like the laryngeal framework surgery, a method used when UVFP has been ongoing for a while. This involves the placement of implants into the voice box to improve vocal fold function. Moreover, laryngeal reinnervation is a method employing other functioning nerves around the voice box to revive voice tone and movement.

In rare or severe cases, another procedure called arytenoid adduction is used. Here a suture is placed from the muscle process of the voice box to the thyroid cartilage. This helps the muscles imitate the function of the vocal fold’s movement. Although rarely used alone, this procedure proves helpful for some patients with UVFP.

What else can Unilateral Vocal Fold Paralysis be?

When diagnosing Unilateral Vocal Fold Paralysis (UVFP), doctors consider several other conditions that can display similar symptoms. These include:

• Allergies and environmental asthma
• Anaphylaxis (serious allergic reaction)
• Asthma
• Bilateral vocal fold paralysis (both sides of the voice box are paralyzed)
• Epiglottitis (inflammation of the tissue that covers the windpipe)
• Exercise-induced asthma
• Foreign body obstruction (something stuck in the airways)
• Laryngeal abnormalities (abnormalities in the voice box)
• Laryngeal edema from C1 inhibitor deficiency or ACE inhibitor use (swelling in the voice box due to a specific protein deficiency or certain medications)
• Laryngeal spasm (muscle contractions in the voice box)
• Upper respiratory tract infection
• Vocal polyps and nodules (growths on the vocal cords)

Proper evaluation and judicious use of diagnostic tests can help differentiate UVFP from these conditions.

What to expect with Unilateral Vocal Fold Paralysis

The future health condition for patients with UVFP (unilateral vocal fold paralysis) depends on the root cause of the issue. For majority of the people with UVFP, where the cause is unknown (termed idiopathic), a natural recovery is generally expected. However, when UVFP is caused by tumors or has origins in the central nervous system (the part of the nervous system that includes the brain and spinal cord), the outcomes can be less predictable.

Possible Complications When Diagnosed with Unilateral Vocal Fold Paralysis

There could be several complications arising from UVFP, or vocal cord paralysis, which include:

• Lung infections due to swallowing of food or liquid (aspiration pneumonia)
• Difficulty in breathing (respiratory distress)
• Problems in swallowing (dysphagia)
• Reduced ability to exercise
• Emotional and social problems due to changes in voice

Certain underlying conditions like cancers, chest injuries, and nervous system diseases can result in their own set of unique complications. These may include:

• Weakness (debility)
• Conditions related to cancer that affect different parts of the body (paraneoplastic syndromes)
• Potential death

Preventing Unilateral Vocal Fold Paralysis

Preventing UVFP, or Unilateral Vocal Fold Paralysis, involves addressing its potential causes and reducing the risk of RLN, or Recurrent Laryngeal Nerve, damage. Ways you can help prevent this condition include taking care not to get neck and throat injuries, treating infections quickly, and having regular check-ups with your doctor. Some factors that could lead to UVFP are beyond your control, but keeping healthy overall can help reduce the chance of complications that could result in this condition.

For doctors, surgical procedures in the head and neck area need to be performed carefully to avoid damaging the laryngeal nerve. They should continuously seek to improve their skills in performing common procedures like ETT insertion, which means putting a tube into the windpipe. This can be achieved by ongoing training and practice.