spasmodic dysphonia
Last reviewed 01/2018
This is a rare focal dystonia of the larynx that affects the vocal muscles. This condition causes abnormal speech production with a hoarse or strained voice and often leads to aphonia. In adductor spasmodic dysphonia, paralysis of the thyroarytenoid muscles helps prevent the development of increased subglottic pressure that is associated with vocal spasms. The paralysis of the thyroarytenoid muscles is achieved via injections of botulinum toxin type A. There is a success rate reported of up to 92% and side effects are rare, and generally limited to problems with swallowing.
Ref: BMJ (1997), 315, 354-60.