Bilateral Vocal Fold Paralysis
What causes bilateral vocal fold paralysis?
Bilateral paralysis of the vocal folds usually happens for one of four reasons: nerve injury during a number of common surgeries, pressure on the nerves from a tumor growing next to them, stroke or other brain injury, or inflammation that stops the nerves from working, usually attributed to viral infection. There are dozens of other less common causes.
Bilateral vocal fold paralysis may be an inadvertent result of surgery, most commonly thyroid surgery. Paralysis of the vocal fold is not necessarily a sign that the nerve has been cut. The nerve may also stop working if stretched or squeezed, and sometimes after surprisingly little handling. For this reason a vocal fold may be paralyzed after even the smoothest of operations.
Another possibility that must be explored in bilateral paralysis is that the vocal folds are scarred in place from damage from a breathing tube rather than paralyzed. Electromyography (see below) can be helpful in this.
In cases of paralysis in persons who have not had surgery or a breathing tube, tumors are the most serious concern, with health consequences that reach far beyond voice. Radiologic studies that look over the entire path of the nerves to the larynx, including the chest, are essential. The consensus is that a CT (or CAT) scan with contrast dye is the best study to examine the nerves in the neck and chest. Bilateral paralysis is more likely than unilateral paralysis to be related to stroke or other neurological disease, so a brain scan is usually necessary as well.
In some cases, no reason is found for the vocal fold paralysis, even after appropriate radiologic studies. These are called idiopathic , and usually attributed to viral inflammation. This cannot be proved, and it is important to understand that this is only an assumption.
What are the symptoms of bilateral vocal fold paralysis?
In bilateral vocal fold paralysis, the vocal folds are unable to open, which causes narrowing and blockage of the airway. The amount of space left between the immobile vocal folds determines the degree of the blockage. There is almost always noisy breathing and breathlessness during activity. Sometimes, this is mistaken for asthma by both physician and patients, which is a dangerous mistake, for bilateral vocal fold paralysis has a very real chance of causing a life-threatening blockage of the airway. Two scenarios in which this may happen are when bilateral vocal fold paralysis occurs unexpectedly following a surgery, or if additional swelling of the vocal folds, as during a common cold, blocks the remaining airway in somebody with a known or unknown bilateral paralysis.
Figure 1A &B: This shows the full range of motion of the vocal folds in a patient with bilateral vocal fold paralysis after thyroid surgery. The vocal folds are closed for voicing at left, and open for breathing at right.
What does bilateral vocal fold paralysis look like?
Vocal fold paralysis is diagnosed by a lack of movement in both vocal folds. Usually this is obvious, but the activity of neighboring muscles may occasionally give the illusion of vocal fold motion. Putting the larynx through a series of motions such as repeated voicing and sniffing will usually clear up any confusion.
Figure 2A &B: Patients with bilateral vocal fold palsy have more trouble (and make more noise, called “stridor”) breathing in than breathing out. These images show why. At left, the patient is exhaling. At right, the patient is inhaling. The suction of the inhalation draws the paralyzed vocal folds together, narrowing the airway and increasing the obstruction.
How is bilateral vocal fold paralysis treated?
Initial (and sometimes emergency) treatment of bilateral paralysis is aimed at making sure the airway will not be blocked. This requires a tracheostomy, which is the creation of a surgical opening from the skin to the trachea . Subsequently, some cases of paralysis recover by themselves. Neither resting the voice nor exercising the vocal folds has been shown to have any effect on recovery. Similarly, no medicine has been proven to help, though some otolaryngologists will prescribe steroids in the belief that they reduce inflammation that has caused the nerve to stop working. In the event that the paralysis recovers, the tracheostomy is reversible.
Some physicians have found electromyography (EMG) to be useful, both to diagnose paralysis and help determine how likely it is that it will recover on its own. EMG is performed by putting needles into the muscles of the larynx though the skin of the neck for a few minutes to record electrical activity. EMG results are not always straightforward, “yes-or-no” type information, but are often very helpful in making subtle diagnoses and treatment decisions.
If the vocal folds do not recover, it is possible to continue indefinitely with a tracheostomy to ensure the airway is open. Removing the tracheostomy, however, requires that the airway be widened, most commonly by surgically removing the part of the vocal fold. This is an irreversible procedure, which may cause voice and swallowing to become worse, and should be considered carefully.