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Spasmodic dysphonia (SD), also known as laryngeal dystonia, is a neurologic voice disorder that is characterized by jerky, strained, strangled and sometimes unintelligible speech. Intermittent vocal interruptions (vocal spasms) and periods of voice loss may alternate with periods of near normal voice. It is estimated that 20,000 adults in the United States have this disorder. The condition can range from interfering mildly with an individualsâs ability to communicate, to being socially incapacitating and unemployable. In SD, the muscles of the larynx fail to relax properly, resulting in abnormal function of the vocal cords. The cause is unknown but evidence suggests a genetic origin for some cases, and a central neurologic source in most cases.
Although there is no known cure for SD, treatment with injections of botulinum toxin (BT) into the muscles of the larynx has recently become the preferred treatment. BT blocks the release of acetylcholine, a neurotransmitter that helps transmit electrical signals from the central nervous system to the muscles of the larynx and causes them to constrict. By blocking acetylcholine release, BT causes the muscles of the larynx to relax and thereby alleviates some of the symptoms of SD. This treatment is very safe and effective. However, the effects of BT are only temporary and patients must return for repeat injections usually at intervals of three to six months. Other treatment options for SD include speech therapy and surgery. Surgical treatment is generally reserved for patients whose symptoms don't respond to more conservative measures. The most effective surgical procedures are recurrent laryngeal nerve section and denervation/reinnervation surgery of the larynx.
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