The inability of one or both vocal cords to move because of damage to the nerves that control the muscles of the larynx or damage to the brain. Opening and closing of the vocal cords have a vital role in speech, swallowing, and breathing. Any impairment in their ability to move can affect these essential functions. The cartilage that attaches the vocal folds may become locked in place and restrict movement of the folds. Accumulated scar tissue can also prevent the vocal folds from moving normally.