Every patient with an unexplained vocal cord paralysis must be investigated. The majority of paralyses involve the left vocal cord, and here a chest X-ray is essential to exclude a lung cancer. If there are symptoms of difficulty in swallowing, a barium-swallow X-ray is required, and if the entire vagus nerve is paralysed (indicated by weakness of the palate on the same side), X-rays of the skull base may be of value. The nose and throat are completely examined in the clinic, and the neck is carefully palpated. If these investigations reveal no cause for the vocal cord paralysis, a full endoscopic assessment is carried out in the operating theatre including examination of the larynx, post-nasal space, hypopharynx, upper oesophagus and bronchial tree.