Dystonias and Other Movement Disorders
Dystonias are most often characterized by a sustained contraction that produces a torsion or twisting action, and can also be associated with spasmodic contractions. The exact cause of dystonias is still unknown, although the disorder is felt to originate in part of the brain called the basal ganglia. The basal ganglia is important in the initiation and control of movements in the body. Along with dystonia, other movement disturbances that arise from problems in the basal ganglia include Parkinson's disease, Huntington's disease, and Wilson disease.
There are several different ways to classify dystonias. For example, dystonia can be classified by the groups of muscles involved using the following terms:
Although dystonias do not always fit neat categories, generalized dystonias usually involve a large number of muscle groups, while focal dystonias affect a specific group of muscles. Falling somewhere in between are the segmental dystonias.
Generalized dystonia is also called idiopathic torsion dystonia. It usually begins during childhood in one arm or leg and over time progresses to involve other extremities. Walking may be affected first, and eventually most other muscles become involved.
Focal dystonias affect a small number of muscles. Many of them occur in the head and neck region. The most common ones are:
- Blephrospasm, rapid blinking of the eyelids.
- Torticollis (also called wry neck), turning of the head to one side.
- Spasmodic dysphonia, strained or breathy speech.
- Oromandibular dystonia, involuntary jaw opening and tongue movement.
- "Writers Cramp", a dystonia affecting the hand and arm muscles, usually occurring with intended movement of these muscles.
There is no specific test for dystonias, and the diagnosis is often made based on the clinical signs and symptoms. Diagnosis may be difficult because the symptoms may resemble those of other neurological disorders.
Certain dystonias are known to be genetic. These forms of dystonia are most often inherited in an autosomal dominant pattern with variable penetrance. This means that 50% of the offspring of individuals with carry the gene for dystonia, but a variable percentage of them will actually develop dystonia. A gene for idiopathic torsion dystonia has recently been discovered. The gene, known as DYT1, is located on chromosome 9.
There are different forms of treatment for dystonia, depending on which muscles are involved and the extent of the disease. On other pages on this site, a description of treatment for spasmodic dysphonia using injections of botulinum toxin (Botox) is given.
For more information about dystonias, look also at the website for the Dystonia Medical Research Foundation at http://www.dystonia-foundation.org
(describes both adductor and abductor spasmodic dysphonia)
(includes a discussion about Botox, also known as botulinum toxin)