People have one set of two vocal cords, also known as vocal folds, that work together in your voice box to produce sound. They are shaved like a V with the apex in the front. They open when you breathe in to let the air flow through to your lungs, and they close and vibrate when you speak (this is called phonation).To produce adequate voice, both vocal cords should move toward each other and close completely to vibrate together (this is called glottic closure).
Your vocal cords move through the contraction of various muscles controlled by your brain and a specific set of nerves. Vocal cord paralysis and paresis can result from abnormal function of the nerves that control your voice box muscles (laryngeal muscles). Paralysis is a complete absence of vocal cord movement, caused by a complete loss of nerve input; paresis is a weakened vocal cord movement, caused by a partial loss of nerve input. There are two nerves that can be involved:
- The recurrent laryngeal nerve (RLN) carries signals to different voice box muscles responsible for opening, closing, and adjusting tension in the vocal cords. Healthy function of this nerve is needed for breathing, speaking, coughing, and swallowing.
- The RLN goes into the chest cavity and curves back into the neck until it reaches your voice box. Because the nerve is relatively long and takes a “detour” to the voice box, it can be damaged or compressed by tumors in the neck or chest, or injured after surgery to the neck or chest.
- The superior laryngeal nerve (SLN) carries signals to a small muscle (called the cricothyroid) that controls your pitch. This muscle adjusts the tension of the vocal cord for high notes during singing (like a guitar string). An injury or damage to the SLN can cause inability to increase pitch when singing or reach higher notes.
Depending on your needs, vocal cord paralysis can cause great difficulty, or only mild problems. For instance, if you’re a professional singer, even mild paresis might end your career; if you’re a computer programmer, however, you might see little ill effect. In some cases mild changes in function of the vocal cords can significantly impact swallowing. Swallowing difficulties can be the first sign of vocal fold paresis.
Symptoms of paralysis and paresis of the vocal cords can include:
- Voice changes—Hoarseness, breathy voice, weak voice, gurgling quality to the voice, shortness of breath after speaking
- Airway problems—Shortness of breath with efforts, noisy breathing, unsuccessful cough
- Swallowing problems—Choking or coughing when swallowing food, drink, or saliva, and food sticking in throat
These symptoms can be mild to severe depending on the degree of paralysis, and the ability of your voice box to adapt. Depending on the cause, your symptoms may resolve with time or persist
Even when vocal paresis is temporary, intervention can be beneficial and necessary. The vocal cords can be assessed in the office with mirror or endoscopic exam. Usually the first intervention is injection of temporary gel to restore proper glottic closure. If function fails to return, more lasting substance can be injected or implanted. Often normal swallow and voice can be achieved.
It is important to evaluate vocal cord paresis as it can be the first evidence of a more significant abnormality. Hoarseness and swallowing problems that result from vocal cord paralysis can be effectively treated, but diagnosis of underlying cause of the vocal cord paralysis is paramount.
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