Spasmodic dysphonia: A voice disorder caused by involuntary movements of one or more muscles of the larynx or voice box. People who have spasmodic dysphonia may have occasional difficulty saying a word or two or they may experience sufficient difficulty to interfere with communication. Spasmodic dysphonia causes the voice to break or to have a tight, strained, strangled or effortful quality. Spasmodic dysphonia can affect anyone. It most often becomes evident between 30 and 50 years of age. More women are affected by spasmodic dysphonia than men. Also called spastic dysphonia and laryngeal dystonia.

There are three different types of spasmodic dysphonia: adductor spasmodic dysphonia, abductor spasmodic dysphonia and mixed spasmodic dysphonia:

• Adductor spasmodic dysphonia -- A form of spasmodic dysphonia in which sudden involuntary muscle movements or spasms cause the vocal folds (or vocal cords) to slam together (adduct) and stiffen. These spasms make it difficult for the vocal folds to vibrate and produce voice. Words are often cut off or difficult to start because of the muscle spasms. Therefore, speech may be choppy and sound similar to stuttering. The voice of an individual with adductor spasmodic dysphonia is commonly described as strained or strangled and full of effort. Surprisingly, the spasms are usually absent while whispering, laughing, singing, speaking at a high pitch or speaking while breathing in. Stress, however, often makes the muscle spasms more severe.
• Abductor spasmodic dysphonia -- A form of spasmodic dysphonia in which sudden involuntary muscle movements or spasms cause the vocal folds to open (abduct). The vocal folds can not vibrate when they are open. The open position of the vocal folds also allows air to escape from the lungs during speech. As a result, the voices of these individuals often sound weak, quiet and breathy or whispery. As with adductor spasmodic dysphonia, the spasms are often absent during activities such as laughing or singing.
• Mixed spasmodic dysphonia -- A form of spasmodic dysphonia involving the muscles that open the vocal folds as well as the muscles that close the vocal folds. Mixed spasmodic dysphonia therefore has features of both adductor and abductor spasmodic dysphonia.

The basic cause of spasmodic dysphonia is unknown. Because the voice can sound normal or near normal at times, spasmodic dysphonia was once thought to be psychogenic. While psychogenic forms of spasmodic dysphonia exist, there is increasing evidence that most cases of spasmodic dysphonia are neurogenic (of neurologic origin).

Spasmodic dysphonia may co-occur with other movement disorders such as blepharospasm (excessive eye blinking and involuntary forced eye closure), tardive dyskinesia (involuntary and repetitious movement of muscles of the face, body, arms and legs), oromandibular dystonia (involuntary movements of the jaw muscles, lips and tongue), torticollis (involuntary movements of the neck muscles), or tremor (rhythmic, quivering muscle movements).

Spasmodic dysphonia runs in some families and is thought to be inherited. Research has identified a possible gene on chromosome 9 that may contribute to the spasmodic dysphonia that is common to certain families. In some individuals the voice symptoms begin following an upper respiratory infection, injury to the larynx, a long period of voice use, or stress.

The diagnosis of spasmodic dysphonia is usually made based on identifying the way the symptoms developed as well as by careful examination of the individual. Most people are evaluated by a team that usually includes an otolaryngologist (an ear, nose and throat physician), a speech-language pathologist (a professional trained to diagnose and treat speech, language and voice disorders) and a neurologist. The otolaryngologist examines the vocal folds to look for other possible causes for the voice disorder. Fiberoptic nasolaryngoscopy, a method whereby a small lighted tube is passed through the nose and into the throat, is a helpful tool that allows the otolaryngologist to evaluate vocal cord movement during speech. The speech-language pathologist evaluates the patient's voice and voice quality. The neurologist evaluates the patient for signs of other muscle movement disorders.

There is presently no cure for spasmodic dysphonia. Current treatments only help reduce the symptoms of this voice disorder. Voice therapy may reduce some symptoms, especially in mild cases. An operation that cuts one of the nerves of the vocal folds (the recurrent laryngeal nerve) has improved the voice of many for several months to several years but the improvement is often temporary. Others may benefit from psychological counseling to help them to accept and live with their voice problem. Still others may benefit from job counseling that will help them select a line of work more compatible with their speaking limitations.

The most promising treatment to relieve the symptoms of spasmodic dysphonia currently appears to be injections of very small amounts of botulinum toxin (botox) directly into the affected muscles of the larynx. Botox injections generally improve the voice for a period of three to four months after which the voice symptoms gradually return. Reinjections are necessary to maintain a good speaking voice. Initial side effects that usually subside after a few days to a few weeks may include a temporary weak, breathy voice or occasional swallowing difficulties. Botox may relieve the symptoms of both adductor and abductor spasmodic dysphonia.