Abstract
Early onset torsion dystonia (EOTD) is a rare movement disorder characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body. A US study estimated the prevalence at approximately 1 in 30,000. The estimated prevalence in the general population of Europe seems to be lower, ranging from 1 in 330,000 to 1 in 200,000, although precise numbers are currently not available. The estimated prevalence in the Ashkenazi Jewish population is approximately five to ten times higher, due to a founder mutation. Symptoms of EOTD typically develop first in an arm or leg in middle to late childhood and progress in approximately 30% of patients to other body regions (generalized dystonia) within about five years. Distribution and severity of symptoms vary widely between affected individuals. The majority of cases from various ethnic groups are caused by an autosomal dominantly inherited deletion of 3 bp (GAG) in the DYT1 gene on chromosome 9q34. This gene encodes a protein named torsinA, which is presumed to act as a chaperone protein associated with the endoplasmic reticulum and the nuclear envelope. It may interact with the dopamine transporter and participate in intracellular trafficking, although its precise function within the cell remains to be determined. Molecular genetic diagnostic and genetic counseling is recommended for individuals with age of onset below 26 years, and may also be considered in those with onset after 26 years having a relative with typical early onset dystonia. Treatment options include botulinum toxin injections for focal symptoms, pharmacological therapy such as anticholinergics (most commonly trihexiphenydil) for generalized dystonia and surgical approaches such as deep brain stimulation of the internal globus pallidus or intrathecal baclofen application in severe cases. All patients have normal cognitive function, and despite a high rate of generalization of dystonia, 75% of those patients are able to maintain ambulation and independence, and therefore a comparatively good quality of life, with modern treatment modalities.
Highlights
Onset torsion dystonia (EOTD) is a rare movement disorder characterized by involuntary, repetitive, sustained muscle contractions or postures involving one or more sites of the body
Molecular genetic diagnostic and genetic counseling is recommended for individuals with age of onset below 26 years, and may be considered in those with onset after 26 years having a relative with typical early onset dystonia
Onset torsion dystonia (EOTD) is characterized by involuntary, repetitive, sustained muscle contractions or postures, typically of the limbs, which may spread to other body parts, in the absence of other neurological abnormalities
Summary
Molecular genetic diagnostic in conjunction with genetic counseling is recommended for individuals with age of onset below 26 years, and may be considered in those with onset after 26 years having a relative with typical early onset dystonia [7]. Onset parkinsonism A considerable proportion of early onset Parkinson's disease, with onset of symptoms before 40 years of age, is caused by mutations in the Parkin gene [47] and frequently presents with dystonia, especially in the lower limbs [48] This condition should be considered in the differential diagnosis of EOTD. Surgical approaches Due to technical advances in recent years, interest in functional surgical approaches in dystonia has been renewed, in particular deep brain stimulation (DBS) of the globus pallidus and pallidotomy (reviewed in [56]) Experience with this approach is still limited, preliminary results in patients with primary generalized dystonia, especially DYT1 GAG deletion carriers, are very promising [57]. Http://www.OJRD.com/content/1/1/48 further evidence for or against direct involvement of the dopaminergic system in EOTD is warranted
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