What is spasmodic dysphonia?
This page will give a brief description of the voice disorder known as spasmodic dysphonia. A separate page describes treatment of spasmodic dysphonia using Botox injections.
Spasmodic dysphonia (SD) is a type of disease known as a dystonia. A dystonia is a disorder of the central nervous system in which there is increased contraction of the muscles. This disorder can affect a large number of muscles, which is called a generalized dystonia, or it can affect just one or two muscle groups in which it is called a focal dystonia. More information on dystonias is available.
Spasmodic dysphonia is a dystonia in which affects only the muscles of the larynx. Other examples of focal dystonia are torticollis (wry neck), blephrospasm (eye-twitching), and writer's cramp.
The exact cause of this dystonia is currently unknown, but is believed to involve a region deep in the brain called the basal ganglia. In spasmodic dysphonia, this area of the brain sends incorrect messages to the muscles controlling the movement of the vocal folds, causing them to contract inappropriately.
There are several types of spasmodic dysphonia. The most common is called adductor SD and it occurs when the muscles that bring the vocal folds together contract too strongly. (A description of the anatomy and function of the larynx is given elsewhere. "Adduction" is the term used when the vocal folds come together. Opening of the vocal folds is called "abduction"). In adductor SD the voice has a very strained or strangled sound, with occasional breaks when the air cannot escape. These breaks are most evident in words that begin with vowels.
Abductor SD is less common. In this disorder the spasms occur in the muscles that open the vocal folds. As a result it is difficult to bring the vocal folds together to produce vowels sounds.
There can also be a mixed spasmodic dysphonia affecting both opening and closing of the vocal folds, and also a version dominated by tremor.
Spasmodic dysphonia is worsened in stressful situations, and therefore may be mistaken attributed only to stress. (It is important to remember that there certainly can be severe voice disorders arising from stress alone; however, these type of voice disorders are best treated with speech therapy and not with Botox.) SD also is often worse on the telephone. It is better with non-verbal vocalization like sighing and laughing, and also is less severe with singing or a high-pitched voice.
Spasmodic dysphonia is not very common and as a result many physicians are not familiar with it. As a result, individuals with SD often are told that their voice disorder is due to nervousness, laryngitis, reflux, etc. However, voice disorders can from SD can at times sound similar to these and other conditions, so the diagnosis of SD is not always clear-cut. Some tests, such as laryngeal electromyography, may be useful, but the diagnosis is most often made by a combination of patient history and careful examination of the larynx.
The most widely form of treatment for spasmodic dysphonia is injection of a long acting muscle relaxant called botox.
(includes a discussion on movement disorders and different types of dystonia)
(includes a discussion about Botox, also known as botulinum toxin)