Focal dystonia is a neurological condition affecting a muscle or muscles in a part of the body causing an undesirable muscular contraction or twisting. For example, in focal hand dystonia, the fingers either curl into the palm or extend outward without control.
Dystonia, idiopathic torsion: A form of dystonia known as early-onset torsion dystonia (also called generalized torsion dystonia) begins in childhood around the age of 12. Symptoms typically start in one part of the body, usually in an arm or leg, and eventually spread to the rest of the body within about 5 years. Early-onset torsion dystonia is not fatal, but it can be severely debilitating.
Primary dystonia (previously called idiopathic dystonia or dystonia musculorum deformans) is often hereditary, although sporadic forms may occur. Early-onset primary torsion dystonia is an autosomal dominant disorder most commonly associated with the mutation of the DYT1 gene. Dystonia occurs as the sole disorder in these individuals and is not related to any other underlying neurological or medical condition.
Secondary dystonia (symptomatic dystonia) may occur as the result of other neurological conditions. These conditions may include multiple sclerosis, Wilson's disease, perinatal ischemic injury, post-traumatic events (e.g., motor vehicle accident), or a side effect of medication. The most common form of secondary dystonia is tardive dystonia, which is caused by chronic use of neuroleptics, antiemetic drugs, or antipsychotic drugs. Other disease-causing factors include neurotransmitter abnormalities and basal ganglia dysfunction. Some ethnic groups, particularly Ashkenazi Jews, have also been shown to be inclined to certain forms of dystonia. Dystonia may be a feature of other movement disorders, such as Parkinson's disease or Huntington's disease.
SOURCES
National Institute of Neurological Disorders and Stroke. (2007). Dystonias Fact Sheet. Retrieved October 31, 2007. http://www.ninds.nih.gov/disorders/dystonias/detail_dystonias.htm.
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