Vocal fold paralysis, or paresis, results from an injury or lesion in the peripheral (surface) or central nervous system controls for voice production. Paralysis may involve one (unilateral) or both (bilateral) vocal folds. In the case of unilateral vocal fold paralysis, one vocal fold moves appropriately but the other does not. If there is bilateral vocal fold paralysis, breathing or voice quality may be affected. When one vocal fold is weak or unable to meet at midline during speaking, air will escape too quickly and the voice will sound weak or breathy. The escape of air often requires the patient to breathe in more often during speaking and, in general, use more effort during speech. This increased effort can result in fatigue. Patients with unilateral vocal fold paralysis are also at risk for choking on foods and liquids.
When both vocal folds are paralyzed, breathing and swallowing problems may be more serious. When the vocal folds are paralyzed in the midline position, vocal quality may be adequate, but normal breathing may be obstructed. Sometimes these patients require the placement of a tracheotomy to establish an appropriate airway. When the vocal folds are paralyzed in an open position, the patient is aphonic (does not have a voice or is just a whisper) and protection of the airway during swallowing is a serious concern.