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.

Finding a cause for paralyzed vocal folds can be simple, as in symptoms that begin immediately after thyroid surgery, or very challenging. A meticulous history is the most important element in this search, aided by appropriate scans. A diagnosis of idiopathic vocal fold can only be made after all other possibilities have been eliminated.

In rare cases, people with two paralyzed vocal folds live for some time without tracheostomy, generally because they have not been aware of the condition. Even in these instances, living without a tracheostomy is not necessarily safe. The degree of risk should be discussed with your physician in order to make an informed choice.