Dysphonia
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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.
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The three types of spasmodic dysphonia are adductor spasmodic
dysphonia, abductor spasmodic dysphonia and mixed spasmodic dysphonia.
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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.
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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.
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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 personšs 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.
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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.
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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.
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American Academy of Neurology
American Academy of Otolaryngology-Head and Neck
Surgery
American Speech-Language-Hearing Association
Dystonia Medical Research Foundation
National Spasmodic Dysphonia Association
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