Unilateral Vocal Fold Paralysis
What causes unilateral vocal fold paralysis?
Most unilateral paralysis of the vocal folds happens for one of three reasons: nerve injury during a number of common surgeries, pressure on the nerve from a tumor growing next to it, or inflammation that stops the nerve from working, usually attributed to viral infection. Together, these three scenarios account for more than 85% of cases of paralyzed vocal folds. There are dozens of other less common causes like stroke and other neurologic disease, and side effects of certain drugs and toxins.
Vocal fold paralysis may be an inadvertent result of several common surgeries, listed in the table. These include heart and lung operations, because the principal nerve of the vocal folds dips into the chest before returning to the larynx. 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. Finally, branches of the nerve may also be damaged by the breathing tube put in for general anesthesia.
Surgeries which may result in vocal fold paralysis:
- Thyroid surgery
- Carotid endarterectomy
- Spinal surgery in the neck (anterior cervical diskectomy)
- Cardiac surgery (especially aortic valve surgery)
- Lung surgery (usually only on the left)
- Repair of aortic aneurysms in the chest
- Brain surgery for aneurysm or tumor
In cases of paralysis in persons who have not had surgery that may damage the nerve, 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 of the neck and chest with contrast dye is the minimum study required to examine the nerves adequately. Lung cancers are the most common tumors to cause vocal fold paralysis.
In some 15-20% of 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. It is important to understand that this is only an assumption.
What are the symptoms of unilateral vocal fold paralysis?
In unilateral paralysis, the vocal folds are unable to close, which causes voice and swallowing problems. The voice is hoarse, breathy and soft, and speaking above background noise is a challenge. Patients get winded when speaking, because so much air is needed to make the vocal folds vibrate. This is commonly mistaken for shortness of breath caused by a lung problem by both doctors and patients. Sometimes, muscles not usually involved in voicing will act to try to bring the vocal folds together, which can give a person a sore neck after prolonged speaking. Occasionally, voice changes will be accompanied by coughing when swallowing. This is especially noticeable when drinking liquids.
Figure 1: The vocal fold on the right of the image is paralyzed after a lung operation. This is the typical appearance of a paralyzed vocal fold during quiet breathing.
Figure 2A &B: The vocal fold on the left of the images is paralyzed. Even with extreme effort, the opposite vocal fold cannot meet its partner (right).
What does unilateral vocal fold paralysis look like?
Vocal fold paralysis is diagnosed by a lack of movement in a vocal fold. Sometimes 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 3: In this patient with longstanding vocal fold paralysis, the paralyzed vocal fold has lost muscle mass and has become thin and atrophic.
How is unilateral vocal fold paralysis treated?
Some cases of vocal fold 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. It is reasonable to try voice therapy while waiting for the nerve to recover, in order to learn how to obtain the best voice in the meantime.
Some physicians have found a test known as 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 through 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.
In most cases of unilateral vocal fold paralysis, it is possible to restore near-normal conversation voice, even though, so far, it has not been possible to restore motion to an immobile vocal fold. Treatment is based on repositioning the immobile vocal fold closer to its partner. This is known as medialization. The details of this are addressed in the treatment section. In brief, though, it can be accomplished by injecting the vocal fold with one of a number of available substances (injection medialization), or by placing a block of artificial material into the larynx through an operation on the outside of the neck (medialization laryngoplasty). Sometimes, this second procedure also involves repositioning the laryngeal cartilages. Each technique has its own advantages and disadvantages, and making an intelligent choice among available treatments depends on discussing these in detail with your physician.