What is vocal fold paralysis? 

Vocal fold paralysis is immobility of a vocal fold because of damage or dysfunction of its principal nerve. This nerve travels from the brain down the neck and into the chest before turning upwards back to the larynx . Because it passes through the neck twice, it is called the recurrent laryngeal nerve. The left-sided nerve is longer than the one on the right and dips lower into the chest, so it is more prone to injury. As a result, the left vocal fold is about twice as likely to be paralyzed as the right.

Vocal fold paralysis can be unilateral (one-sided) or bilateral (two-sided). Because unilateral and bilateral paralyses have slightly different causes, and very different symptoms and treatments, they are best considered separately:

Unilateral Vocal Fold Paralysis           Bilateral Vocal Fold Paralysis