Cricothyroid muscle paralysis: its recognition and diagnosis

Cricothyroid muscle paralysis is often missed as the symptoms are not dramatic and the laryngeal observations, on conventional indirect mirror examination, are inconclusive. The anatomy and physiology of the superior laryngeal nerve (SLN) and cricothyroid muscle are described. Three case reports are presented to illustrate our diagnostic techniques. Videofibrolaryngoscopy and electromyography are found to be invaluable tools for the diagnosis of this condition. The importance in diagnosing this entity is discussed.