Normal voice depends on the vocal folds being brought together by muscles in the larynx (voice box). Usually, the force generated to close the vocal folds is the same on both the right and left sides. Each vocal fold is controlled by its own nerve that provides both motor (movement) and sensory signals. They work together to create closure and produce voice. When the movement control is imperfect, voice disturbances or swallowing difficulties often occur. When the sensory component is affected, patients may experience symptoms such as coughing, laryngeal spasms, or shortness of breath.
Some conditions can weaken the nerves of the vocal folds without causing a complete loss of function. When there is a complete loss of nerve function, resulting in an absence of motion, the condition is called vocal fold paralysis. This is relatively easy to diagnose because the lack of movement is obvious during a throat examination. In contrast, when there is only some weakness and not a complete loss of movement, the condition is called vocal fold paresis.
One common cause of vocal fold paresis is a recent viral illness. Many viruses have been implicated in causing temporary weakness in nerve conduction. Fortunately, the majority of vocal fold paresis cases due to viral illness are temporary, and recovery is typical. However, a small percentage of patients do not recover fully, resulting in long-term voice or throat symptoms.
Vocal fold paresis presents differently than vocal fold paralysis. Patients with vocal fold paresis may complain of a mildly hoarse voice that becomes tired by the end of the day. Their vocal range may be affected, and producing loud sounds that were once easy may now be challenging. This loss of vocal function is especially problematic for voice professionals and singers who rely on a fully functional voice throughout the day.
To diagnose vocal fold paresis, a high index of suspicion is necessary. A battery of tests is performed during a laryngeal examination to detect differences in the function of one or both vocal folds. Someone unaware of the possibility of vocal fold paresis might observe what appears to be normal vocal fold motion and assume other diagnoses, such as vocal aging, muscle tension dysphonia, laryngeal swelling, or acid reflux—all of which can mimic the symptoms of vocal fold paresis. Following the initial examination, a nerve test called laryngeal electromyography (EMG) is often performed to confirm the presence of nerve weakness and to assess the severity and permanence of the paresis.
Treatment for vocal fold paresis can help improve function. Although recovery from paresis is usually expected, improvement in nerve function is unlikely beyond one year. Speech-language therapy is commonly administered to patients suffering from the symptoms of vocal fold paresis. In some cases, laryngologists may perform temporary or permanent interventions to “bulk up” the vocal folds. Augmentation can be achieved with injections (such as Restylane or fat) or implants, and these procedures may be done in the office or in the operating room to enhance vocal function.
