Spasmodic dysphonia (SD)

Description. Spasmodic dysphonia (SD) is a type of “focal dystonia”. In general, a focal dystonia is a condition in which movement is abnormal in an isolated body part, especially during meaningful tasks (such as speech). In spasmodic dysphonia, which affects voice, vegetative functions such as cough as coughing, laughing, and even singing may be normal. Two types of SD are recognized. In adductory SD (AD-SD), the more common type, as the vocal folds themselves may fail to come together and mainatain normal contrast.

Causes. The exact causes of SD are unknown. However, in many cases, the cause appears to involve a minor nerve or brain abnormality that is unrelated to any other disease. The abnormality does not cause any other problems besides speech problems. For AD-SD, one set of research findings suggests that the cause may involve abnormal reactions to stimulation of the vocal fold nerves.

Treatment. Currently, the main treatment of choice for SD involves the use of very small amount of “botulinum toxin” (also called “botox”) injected into one or both vocal folds or in other muscles near them. With this injection, the treated vocal fold is temporarily weakened and the spasms are reduced. When the effects wears off, usually within about 3-5 months, spasms tend to recur and the patient returns for another injection. There is some evidence that a limited number of voice therapy sessions, aimed at minimizing the force vocal fold contact (for AD-SD), may enhance the effect of the “botox” and make it work longer. When SD-like symptoms are related to stress, voice therapy is the treatment of choice. In such cases, therapy may focus on stretching and relaxation.