Illustration of a larynx, also known as the voice box, showing vocal cord paralysis. The vocal cords (upper frame) are responsible for the production of sound, and when brought close together they vibrate and emit sounds as air is expelled from the lungs. Here they are asymmetric as one of the sides is paralysed due to nerve damage. Paralysis can cause problems with speech and swallowing and in severe cases breathing. Treatment is with voice therapy or surgery if that is unsuccessful.