Recurrent Laryngeal Nerve Paralysis
Unilateral and Bilateral
Vocal fold paralysis is the most common neurogenic voice disorder. Vocal fold paralysis may be bilateral or unilateral and is typically caused by nerve involvement of the recurrent laryngeal nerve and, less commonly, the superior laryngeal nerve. The location and type of the injury along the nerve pathway will determine the type of paralysis and the resultant voice quality. There are many possible causes of vocal fold paralysis including surgical trauma, cardiovascular disease, neurological diseases, and accidental trauma. Historically, estimates of idiopathic (unknown cause) vocal fold paralysis were approximately 30 to 35%. In cases of idiopathic onset of paralysis, patients frequently report that hoarseness began following a viral infection.
Patients with unilateral vocal fold paralysis present with varied vocal symptoms, ranging from mild to severe dysphonia. The characteristic perceptual symptoms of paralysis are breathiness, low intensity, low pitch, and intermittent diplophonia (production of two pitches at one time). Patients with this pathology often complain of physical fatigue resulting from the increased effort to produce voice and the breathlessness associated with phonation. Treatment approaches for unilateral adductor paralysis include a large range of behavioral, surgical, and combination approaches. The most serious form of vocal fold paralysis is a bilateral impairment. When both vocal folds are paralyzed in the midline position they cannot open to create sufficient airway for respiration. This critical condition is called bilateral abductor paralysis and requires that an adequate airway be established surgically, often through a tracheostomy.
When bilateral paralysis occurs with vocal folds positioned in an open position, breathing is no longer a concern, but protecting the airway during swallowing becomes a much larger threat. This condition is termed bilateral adductor paralysis, and in this configuration, neither voice production nor airway protection can be achieved satisfactorily. Patients with this form of paralysis often require gastrostomy tube feedings and augmentative communication aids, due to the complete aphonia.
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