Conditions: Vocal Cord Weakness (Paresis) or Paralysis
Vocal cord paresis is weakness, and paralysis is absent movement, of one or both vocal cords, most often from injury to the nerve that controls the voice box. The condition can affect the voice, swallowing, and breathing.
What Vocal Cord Paresis and Paralysis Are
The vocal cords (also called vocal folds) are two bands of tissue inside the voice box (larynx). They open during breathing and close during speaking, swallowing, and coughing. Each vocal cord is controlled by a nerve called the recurrent laryngeal nerve, which branches off a larger nerve (the vagus nerve) that runs from the brain, down the neck, and into the chest before returning to the voice box.
Vocal cord paralysis happens when one or both vocal cords cannot move because the nerve signal to the muscle is interrupted. The cord then sits in a fixed position and cannot close properly against the other cord. Vocal cord paresis is a partial version of the same problem: the nerve still works, but weakly, so the cord moves less well than normal. Most often only one side is affected (unilateral paralysis or paresis). The left side is affected far more often than the right because the left nerve travels a longer path down into the chest.
Symptoms and Signs
The symptoms depend on whether one or both cords are affected.
When one vocal cord is weak or paralyzed, common symptoms include:
A hoarse, breathy, or weak voice. This is usually the first and most noticeable problem. The voice may sound like a whisper and tire easily. Hoarseness has many possible causes, which are described on the voice problems page.
Running out of air when speaking, or needing to take frequent breaths.
Coughing or choking while eating or drinking, especially with thin liquids.
A weak cough that does not clear the throat well.
A feeling of something stuck in the throat, or throat discomfort.
When both vocal cords are paralyzed, the main concern shifts to breathing. Because the cords can sit close together and narrow the airway, symptoms can include shortness of breath and a high-pitched, noisy sound when breathing in (stridor). This can be a medical emergency. Other causes of a narrowed airway include subglottic stenosis and sudden spasm of the vocal cords (laryngospasm).
What Causes It
Paresis or paralysis results from injury anywhere along the nerve's long path. The most common causes are:
Surgery (the most common cause). Operations near the nerve's path can stretch, bruise, or cut it, including thyroid and parathyroid surgery, surgery on the neck arteries, spine surgery through the front of the neck, and surgery on the chest, heart, lungs, or esophagus. A breathing tube used during anesthesia can occasionally injure the nerve as well. More about voice changes after neck surgery is on the laryngeal nerve dysfunction page.
Tumors or growths in the neck or chest (for example, lung or thyroid tumors) that press on or invade the nerve.
Nerve and brain conditions, such as a stroke, multiple sclerosis, or certain nerve diseases.
Viral infections that inflame the nerve.
Injury to the neck or chest.
Certain chest and heart conditions, such as an enlarged blood vessel (aneurysm) or an enlarged heart chamber pressing on the nerve.
Unknown cause (idiopathic). In a meaningful share of cases, no cause is found despite a thorough search. This is a common finding, not a sign that something was missed.
How It Affects Daily Life
Vocal cord paresis or paralysis can affect three important functions:
Voice and communication. A weak, breathy voice can make it hard to be heard, to talk on the phone, or to speak for long periods. This can be frustrating and tiring, and over time can affect work and social life.
Swallowing. When the cords do not close fully, food or liquid can slip into the airway instead of going down the food pipe. This causes coughing during meals and, in some cases, can lead to a lung infection (aspiration pneumonia). Swallowing difficulty is reported in a large share of people with one-sided paralysis. More information is on the swallowing problems and dysphagia pages.
Breathing and airway protection. A weak cough makes it harder to clear the airway. When both cords are affected, breathing itself can be blocked.
Will It Get Better?
Many people recover on their own. Depending on how badly the nerve was injured, nerve function can return over the first 6 to 12 months. Recovery is more likely when the injury is mild and when it occurred in the neck rather than deep in the chest. If the nerve was completely cut, recovery is not expected. Because recovery can take months, the timing of any treatment usually takes this window into account. Treatment options are described on the treatments for vocal cord paresis or paralysis page. Surgery packets are also available for two procedures used for this condition: injection laryngoplasty and thyroplasty with implant.
The Diagnostic Workup and Why Each Step Is Done
The goal of the evaluation is twofold: confirm that a vocal cord truly is not moving normally, and find out why.
1. History and physical exam. The evaluation typically covers recent surgeries (especially of the neck, thyroid, or chest), breathing-tube use, cancer history, nerve conditions, and recent infections. Why: the cause is often found in this history, since surgery and tumors are leading causes.
2. Looking at the vocal cords (laryngoscopy). An ear, nose, and throat specialist passes a thin, flexible camera through the nose to watch the vocal cords move during breathing and speaking (fiberoptic laryngoscopy). Sometimes a specialized strobe light (stroboscopy) is used for a more detailed look. Why: this is the only way to directly confirm that a cord is not moving and to rule out other causes of a hoarse voice, such as a growth on the cord. Hoarseness lasting more than a few weeks without a clear explanation generally warrants this kind of exam.
3. Imaging (usually a CT scan). If the cause is not already known, a CT scan with contrast dye is typically ordered covering the path of the nerve, from the base of the skull, down the neck, and into the chest. For left-sided paralysis the scan extends lower into the chest, because the left nerve loops down near the heart and the large blood vessels. Why: imaging searches for a tumor or other lesion anywhere along the nerve's route that could be pressing on it. In some situations, particularly when a problem higher up in the brain or skull base is suspected, an MRI may be used instead.
4. Swallowing evaluation. When coughing occurs with eating or drinking, a swallowing study may be done, sometimes using a camera or an X-ray video during swallowing. Why: to check whether food or liquid is entering the airway and to guide safe eating and therapy.
5. Additional testing in selected cases. A specialized nerve-muscle test of the voice box (laryngeal electromyography) is sometimes used to judge how severe the nerve injury is and how likely recovery is. Why: this can help guide the timing of treatment.
When It Is an Emergency
Difficulty breathing, noisy breathing (stridor), or choking that cannot be controlled are emergency symptoms that call for immediate medical attention.
Questions People Often Discuss With Their Care Team
Is one vocal cord affected, or both?
Has a cause been found, and is imaging needed?
How likely is the voice to recover, and over what time frame?
Is it safe to eat and drink normally?
Could voice therapy or a procedure help the voice or swallowing?
More background on the voice is in the voice learning center, and tips for getting ready for a voice visit are on the voice appointment preparation page.