Early Motor Unit Disease Masquerading as Psychogenic Breathy Dysphonia: A Clinical Case Presentation

Abstract

This is a study of a 20-year-old girl who developed mild, breathy dysphonia which, because of its nonspecificity, had been previously diagnosed as psychogenic; in actuality her voice change was a sign of early myasthenia gravis. The case is presented to alert the clinician to the fact that voice changes can be one of the first and only signs of early neurologic disease. Differential diagnosis requires careful laryngologic, psychiatric, speech, and neurologic examinations. In this instance, the laryngologic and psychiatric examinations were nonproductive, but the speech examination elicited a marked increase in breathiness, hypernasality, and articulatory imprecision as the consequence of prolonged, effortful speaking. This finding, along with the neurologist’s demonstration of an increase in muscular strength by means of injecting edrophonium chloride (Tensilon) led to the diagnosis of myasthenia gravis. A summary of the incidence, clinical features, methods of examination, and treatment of this disease follow the case presentation.