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William McK. & Marcia N.Thompson Center for Restorative Neurosurgery
Education & Information
Facts about Dystonia
Dystonia is characterized by involuntary, patterned (sustained or repetitive) muscle contractions or spasms that can cause squeezing, twisting or other movements or abnormal postures. Dystonia can be organized into the following categories:
Focal Dystonia: Affects a single body part such as hand, neck, or eyelids (which is blepharospasm)
Segmental Dystonia: Affects two or more adjacent parts of the body
Hemi-Dystonia or Unilateral Dystonia: Affects one half of the body
Generalized Dystonia: Involves the legs, trunk and other parts of the body
Certain types of focal and segmental dystonias are actually experienced by a wide percentage of the population, although they may be known by more common terms such as writer’s cramp. Other types of “occupational” dystonias affect the performance of musicians, sportsmen and others whose skills depend on finely coordinated movements. In contrast to focal and segmental dystonia, which typically involve no other neurological abnormality and no specific cause except possibly genetic, most patients with hemidystonia have some other factor such as head trauma, stroke, arteriovenous malformation, tumor, encephalitis or other pathology that may have triggered the dystonia.
Childhood Dystonia
One of the most common forms of dystonia in children is DYT1 dystonia. This dystonia, which occurs with particularly high frequency in Ashkenazi Jewish population, is manifested by onset of writer’s cramp, foot inversion or other dystonia of the limbs, typically before the age of 10. It then progresses to a more generalized dystonia involving legs, arms and trunk. Although the progression may vary between individuals of the same or different families, many children with DYT1 dystonia require assistance with ambulation by the time they reach their early teens. The diagnosis of DYT1 dystonia can be confirmed by a genetic DNA test (see below).
Causes
The cause of primary dystonias is not always apparent, but most are probably due to genetic abnormalities. Although no specific abnormality or lesion can be identified by neuroimaging or even autopsy studies in most patients with dystonia, there is convincing evidence that this movement disorder is due to abnormal function of the deep portion of the brain, called basal ganglia. The most important advance in our effort to understand the cause of dystonia has been the identification of a gene, called DYT1 on chromosome 9, the mutation of which causes primary dystonia. Besides DYT1, there are many other genetic forms of dystonia, and new gene abnormalities are being added to the growing list of genetic forms of dystonia.
However, not all dystonias are of genetic origin; some are sporadic (no family history) and others are secondary to some specific causes such as certain metabolic and neurodegenerative disorders (e.g. Wilson's disease), brain injury or other lesions (e.g. cerebral palsy) or certain drugs that block dopamine receptors. The dopamine-receptor blocking drugs, also called neuroleptics, and anti-nausea medications also can cause temporary or persistent dystonia as well. Certain forms of dystonia (particularly focal and segmental dystonia) also may be caused by an injury to the affected body part. Finally, physical or emotional stress and a variety of other psychological factors may be associated with abnormal movements resembling dystonia, the so-called “psychogenic dystonia.”
Treatment
The treatment of dystonia has markedly improved over the years, largely due to the application of botulinum toxin (Botox). Before considering Botox therapy, however, curable causes of dystonia should be considered such as certain drug-induced dystonias or Wilson's disease. Physical therapy, occupational therapy and speech therapy can be helpful as an adjunctive treatment. Some patients, particularly those with generalized dystonia, may benefit from certain medications. Oral medications are sometimes helpful, but can cause side effects in some patients. Surgical techniques, such as local nerve or muscle excision and ablation or high-frequency deep brain stimulation (DBS) have also shown success in patients with disabling. In particular, DBS of the globus pallidus internum (GPi) has emerged as the surgical treatment of choice in patients with severe generalized or segmental dystonia as well as hemidystonia.
For more information, please contact the Dystonia Medical Research Foundation at www.dystonia-foundation.org or www.wemove.org.
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