Spasmodic dysphonia (or laryngeal dystonia) is a voice disorder caused by involuntary movements of one or more muscles of the larynx or voice box. Individuals 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 or strangled quality. There are three different types of spasmodic dysphonia.
The three types of spasmodic dysphonia are adductor spasmodic dysphonia, abductor spasmodic dysphonia and mixed spasmodic dysphonia.
In adductor spasmodic dysphonia, sudden involuntary muscle movements or spasms cause the vocal folds (or vocal cords) to slam together 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.
In abductor spasmodic dysphonia, sudden involuntary muscle movements or spasms cause the vocal folds to open. 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 involves muscles that open the vocal folds as well as muscles that close the vocal folds and therefore has features of both adductor and abductor spasmodic dysphonia.
Spasmodic dysphonia can affect anyone. The first signs of this disorder are found most often in individuals between 30 and 50 years of age. More women appear to be affected by spasmodic dysphonia than are men.
The 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, that is, originating in the affected person¹s mind rather than from a physical cause. While psychogenic forms of spasmodic dysphonia exist, research has revealed increasing evidence that most cases of spasmodic dysphonia are in fact neurogenic or having to do with the nervous system (brain and nerves). 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).
In some cases, spasmodic dysphonia may run in 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 (a physician who specializes in ear, nose and throat disorders), a speech-language pathologist (a professional trained to diagnose and treat speech, language and voice disorders) and a neurologist (a physician who specializes in nervous system disorders). 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.
Currently the most promising treatment for reducing the symptoms of spasmodic dysphonia is injections of very small amounts of botulinum toxin (botox) directly into the affected muscles of the larynx. Botulinum toxin is produced by the Clostridium botulinum bacteria. This is the bacterium that occurs in improperly canned foods and honey. The toxin weakens muscles by blocking the nerve impulse to the muscle. The 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.
American Academy of Neurology
American Academy of Otolaryngology-Head and Neck Surgery
American Speech-Language-Hearing Association
Dystonia Medical Research Foundation