Function of the Vocal Folds and Symptoms of Immobility
A more complete description of the vocal folds and the larynx can be found elsewhere. Briefly, the vocal folds are folds of tissue located in the larynx (voicebox) that have three important functions:
- To protect the airway from choking on material in the throat
- To regulate the flow of air into our lungs
- The production of sounds used for speech.
The front two-thirds of the vocal fold is made up of muscle covered by a thin layer called mucosa. The back one-third is made up of cartilage called the vocal process which is also covered by mucosa. When we speak muscles in the larynx bring the vocal cords together. As the air rushes from our lungs out through the larynx, the from portion of the vocal cords vibrate, producing a sound. The upper portion of our throat then modifies this sound to produce speech.
When we breathe, one pair of muscles spreads the vocal folds apart so that air can easily enter into the lungs.
If one or both of the vocal folds does not move properly, these functions (speech or breathing) may not be normal. The general term of this disorder is vocal fold immobility.
THE SYMPTOMS OF VOCAL FOLD IMMOBILITY
The symptoms of vocal fold immobility depend on whether one or both vocal folds are affected:
UNILATERAL (SINGLE) VOCAL CORD IMMOBILITY
If only one vocal fold is not moving well, the most common symptom is a breathy voice. The weakened vocal fold often cannot move well enough to meet the other fold in the midline during speech and as a result air leaks out too quickly. This causes the voice to sound breathy and weak, and also makes it necessary for the speaker to take breaths more often during speech. After a full day of talking, someone with a weak vocal fold can feel exhausted due to the frequent breathing.
Unilateral vocal folds paralysis can also lead to choking and coughing, especially after eating or drinking liquids. The weakened fold cannot fully close the larynx during swallowing and food or water may leak into the lungs.
Some people with unilateral vocal fold paralysis find it harder to cough and to "bear down" during lifting or straining. All of these actions require that the vocal folds be brought together for a tight seal, and this may not occur if one fold is not moving well.
BILATERAL VOCAL FOLD IMMOBILITY
If both vocal folds have movement problems, the situation may be much more serious. With bilateral vocal fold paralysis, both folds may be in the midline position. This makes it very difficult to breathe and can lead to serious problems. In some cases a tracheotomy is necessary to establish an airway for people with bilateral vocal fold paralysis. However, if both folds are near the center, the voice may be quite good.