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Dystonia (cont.)

When do symptoms of dystonia occur?

Dystonia can occur at any age, but is often described as either early, or childhood, onset versus adult onset.

Early-onset dystonia often begins with symptoms in the limbs and may progress to involve other regions. Some symptoms tend to occur after periods of exertion and/or fluctuate over the course of the day.

Adult-onset dystonia usually is located in one or adjacent parts of the body, most often involving the neck and/or facial muscles. Acquired dystonia can affect other regions of the body.

Dystonias often progress through various stages. Initially, dystonic movements may be intermittent and appear only during voluntary movements or stress. Later, individuals may show dystonic postures and movements while walking and ultimately even while they are relaxed. Dystonia can be associated with fixed postures and shortening of tendons.

How are the dystonias classified?

One way to classify the dystonias is based upon the regions of the body which they affect:

  • ralized dystonia affects most or all of the body.
  • Focal dystonia is localized to a specific part of the body.
  • Multifocal dystonia involves two or more unrelated body parts.
  • Segmental dystonia affects two or more adjacent parts of the body.
  • Hemidystonia involves the arm and leg on the same side of the body.

There are several different forms of dystonia. Some of the more common focal forms are:

Cervical dystonia, also called spasmodic torticollis or torticollis, is the most common of the focal dystonias. In cervical dystonia, the muscles in the neck that control the position of the head are affected, causing the head to turn to one side or be pulled forward or backward. Sometimes the shoulder is pulled up. Cervical dystonia can occur at any age, although most individuals first experience symptoms in middle age. It often begins slowly and usually reaches a plateau over a few months or years. About 10 percent of those with torticollis may experience a spontaneous remission, but unfortunately the remission may not be lasting.

Blepharospasm, the second most common focal dystonia, is the involuntary, forcible contraction of the muscles controlling eye blinks. The first symptoms may be increased blinking, and usually both eyes are affected. Spasms may cause the eyelids to close completely, causing "functional blindness" even though the eyes are healthy and vision is normal.

Cranio-facial dystonia is a term used to describe dystonia that affects the muscles of the head, face, and neck (such as blepharospasm). The term Meige syndrome is sometimes applied to cranio-facial dystonia accompanied by blepharospasm. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. This dystonia may cause difficulties with opening and closing the jaw, and speech and swallowing can be affected. Spasmodic dysphonia, also called laryngeal dystonia, involves the muscles that control the vocal cords, resulting in strained or breathy speech.

Task-specific dystonias are focal dystonias that tend to occur only when undertaking a particular repetitive activity. Examples include writer's cramp that affects the muscles of the hand and sometimes the forearm, and only occurs during handwriting. Similar focal dystonias have also been called typist's cramp, pianist's cramp, and musician's cramp. Musician's dystonia is a term used to classify focal dystonias affecting musicians, specifically their ability to play an instrument or to perform. It can involve the hand in keyboard or string players, the mouth and lips in wind players, or the voice in singers.

In addition, there are forms of dystonia that may have a genetic cause:

  • DYT1 dystonia is a rare form of dominantly inherited generalized dystonia that can be caused by a mutation in the DYT1 gene. This form of dystonia typically begins in childhood, affects the limbs first, and progresses, often causing significant disability. Because the gene's effects are so variable, some people who carry a mutation in the DYT1 gene may not develop dystonia.
  • Dopa-responsive dystonia (DRD), also known as Segawa's disease, is another form of dystonia that can have a genetic cause. Individuals with DRD typically experience onset during childhood and have progressive difficulty with walking. Symptoms characteristically fluctuate and are worse late in the day and after exercise. Some forms of DRD are due to mutations in the DYT5 gene. Patients with this disorder have dramatic improvements in symptoms after treatment with levodopa, a medication commonly used to treat Parkinson's disease.

Recently, researchers have identified another genetic cause of dystonia which is due to mutations in the DYT6 gene. Dystonia caused by DYT6 mutations often presents as cranio-facial dystonia, cervical dystonia, or arm dystonia. Rarely, a leg is affected at the onset.

Many other genes that cause dystonic syndromes have been found, and numerous genetic variants are known to date. Some important genetic causes of dystonia include mutations in the following genes: DYT3, which causes dystonia associated with parkinsonism; DYT5 (GTP cyclohydrolase 1), which is associated with dopa-responsive dystonia (Segawa disease); DYT6 (THAP1), associated with several clinical presentations of dystonia; DYT11, which causes dystonia associated with myoclonus (brief contractions of muscles); and DYT12, which causes rapid onset dystonia associated with parkinsonism.

Medically Reviewed by a Doctor on 12/18/2013

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Source: MedicineNet.com
http://www.medicinenet.com/dystonia/article.htm

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