MONDAY, April 19 (HealthDayNews) -- Botox injections help restore the voices of people with spasmodic dysphonia, a voice disorder caused by vocal cord muscle spasms, according to a University of Michigan study.

The three-year study included 36 people with spasmodic dysphonia. They were treated with Botox injections up to six times. All the patients showed dramatic improvement on the voice-related quality of life (V-RQOL) scale.

The findings appear in the April issue of the Archives of Otolaryngology, Head and Neck Surgery.

This is the first study to offer long-term data on how repeated Botox injections affect the voices of people with spasmodic dysphonia, along with their emotional, social and physical functioning.

For years, Botox has been used off-label to treat people with spasmodic dysphonia. This rare and often-misdiagnosed disorder causes a person's voice to sound strained, broken or breathy. Botox injections relax the vocal cord muscles.

More information

The U.S. National Institute on Deafness and Other Communication Disorders has more about spasmodic dysphonia.