Spasmodic dystonia (SD) is a chronic neurological disorder of the vocal cords where the voice is strained, hoarse, jerky or breathy. It occurs when one or more muscles of the larynx contract or spasm involuntarily during speech without structural abnormality. Speech will sometimes be interrupted and stop altogether during a spasm, then start again when it subsides. Swallowing and breathing remain unaffected.
Symptoms are gradual and usually begin in middle-age, although they can appear at any age. There is a higher rate of occurrence in women. In times of stress or fatigue, the condition can worsen or may disappear completely when laughing or singing.
The cause of spasmodic dystonia is unknown, but it is considered to be genetic and can occur simultaneously with other neurological movement disorders affecting other parts of the body. Treatment options include voice therapy, Botox, and surgery.