What are the dystonias?
The dystonias are movement disorders in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements, which are involuntary and sometimes painful, may affect a single muscle; a group of muscles such as those in the arms, legs or neck; or the entire body. Diminished intelligence and emotional imbalance are not usually features of the dystonias.
What are the symptoms?
Early symptoms may include a deterioration in handwriting after writing several lines, foot cramps, and a tendency of one foot to pull up or drag after running or walking some distance. The neck may turn or pull involuntarily, especially when the patient is tired. Other possible symptoms are tremor and voice or speech difficulties. The initial symptoms can be very mild and may be noticeable only after prolonged exertion, stress or fatigue. Over a period of time, the symptoms may become more noticeable and widespread and be unrelenting; sometimes, however, there is little or no progression.
How are the dystonias classified?
One way to classify the dystonias is according to the parts of the body they affect:
Some patterns of dystonia are defined as specific syndromes:
Torsion dystonia, previously called dystonia musculorum deformans, is a rare, generalized dystonia that may be inherited, usually begins in childhood, and becomes progressively worse. It can leave individuals seriously disabled and confined to a wheelchair.
Spasmodic torticollis, or torticollis, is the most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward. Torticollis can occur at any age, although most individuals first experience symptoms in middle age. It often begins slowly and usually reaches a plateau. About 10 to 20 percent of those with torticollis experience a spontaneous remission, but unfortunately the remission may not be lasting.
Blepharospasm, the second most common focal dystonia, is the involuntary, forcible closure of the eyelids. The first symptom may be uncontrollable blinking. Only one eye may be affected initially, but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal.
Cranial dystonia is a term used to describe dystonia that affects the muscles of the head, face, and neck. Oromandibular dystonia affects the muscles of the jaw, lips, and tongue. The jaw may be pulled either open or shut, and speech and swallowing can be difficult. Spasmodic dysphonia involves the muscles of the throat that control speech. Also called spastic dysphonia or laryngeal dystonia, it causes strained and difficult speaking or breathy and effortful speech. Meige's syndrome is the combination of blepharospasm and oromandibular dystonia and sometimes spasmodic dysphonia. Spasmodic torticollis can be classified as a type of cranial dystonia.
Writer's cramp is a dystonia 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, musician's cramp, and golfer's cramp.
Dopa-responsive dystonia (DRD), of which Segawa's dystonia is an important variant, is a condition successfully treated with drugs. Typically, DRD begins in childhood or adolescence with progressive difficulty in walking and, in some cases, spasticity. In Segawa's dystonia, the symptoms fluctuate during the day from relative mobility in the morning to increasingly worse disability in the afternoon and evening as well as after exercise. Some scientists feel DRD is not only rare but also rarely diagnosed since it mimics many of the symptoms of cerebral palsy.
What do scientists know about the dystonias?
Investigators believe that the dystonias result from an abnormality in an area of the brain called the basal ganglia where the messages to initiate muscle contractions are believed to originate. Scientists suspect a defect in the body's ability to process a group of chemicals called neurotransmitters that help cells in the brain communicate with each other. Some of these neurotransmitters include:
Acquired dystonia; also called secondary dystonia, results from environmental or disease related damage to the basal ganglia. Birth injury (particularly due to lack of oxygen), certain infections, reactions to certain drugs, heavy-metal or carbon monoxide poisoning, trauma, or stroke can cause dystonic symptoms. Dystonias can also be symptoms of other diseases, some of which may be hereditary.
About half the cases of dystonia have no connection to disease or injury and are called primary or idiopathic dystonia. Of the primary dystonias, many cases appear to be inherited in a dominant manner; i.e., only one carrier parent need contribute the dystonia gene for the disease to occur, each child having a 50150 chance of being a carrier. In dystonia, however, there is consider-able variation in the extent to which symptoms are present in an individual carrier, and in how frequently symptoms appear in a specific group of carriers such as a family. This means that a carrier may or may not develop a dystonia and that the symptoms may vary widely even among members of the same family. The product of one defective gene appears to be sufficient to cause the chemical imbalances that may lead to dystonia; but the possibility exists that another gene or genes and environmental factors may play a role.
Some cases of primary dystonia may have different types of hereditary patterns. Knowing the pattern of inheritance can help families understand the risk of passing dystonia along to future generations.
When do symptoms occur?
In some individuals, symptoms of a dystonia appear in childhood between the ages of 5 and 16, usually in the foot or in the hand. In generalized dystonia, the involuntary dystonic movements may progress quickly to involve all limbs and the torso, but the rate of progression usually slows noticeably after adolescence.
For other individuals, the symptoms emerge in late adolescence or early adulthood. In these cases, the dystonia often begins in upper body parts, with symptoms progressing slowly. A dystonia that begins in adulthood is more likely to remain as a focal or segmental dystonia.
Dystonias often progress through various stages. Initially, dystonic movements are 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. Dystonic motions may lead to permanent physical deformities by causing tendons to shorten.
In secondary dystonias due to injury or stroke, people often have abnormal movements of just one side of the body, which may begin at the time of the brain injury or sometime afterward. Symptoms generally plateau and do not usually spread to other parts of the body.
Are them any treatments?
No one treatment has been found universally effective. Instead, physicians use a variety of therapies aimed at reducing or eliminating muscle spasms and pain.
Frequently, the first drug administered belongs to a group that reduces the level of the neurotransmitter acetylcholine. Drugs in this group include trihcxyphenidyl, benztropine, and procyclidine HCI.
Drugs that regulate the neurotransmitter GABA may be used in combination with these drugs or alone in patients with mild symptoms. GABA regulating drugs include the muscle relaxants diazepam, lorazepam, clonazepam, and baclofen.
Other drugs act on dopamine, a neurotransmitter that helps the brain fine-tune muscle movement. Some drugs which increase dopamine include levodopa/carbidopa and bromocriptine. DRD has been remarkably responsive to small doses of this dopamine-boosting treatment. On the other hand, patients have occasionally benefitted from drugs that decrease dopamine, such as reserpine or the investigational drug tetrabenazine.
Anticonvulsants including carbamazepine, usually prescribed to control epilepsy, have occasionally helped individuals with dystonia.
Some patients with spasmodic dysphonia may benefit from treatment by a speech-language pathologist. Physical therapy, splinting, stress management, and biofeedback may also help individuals with certain forms of dystonia.
What research is being done?
The ultimate goals of research are to find the cause(s) of the dystonias so that they can be prevented, and to find ways to cure or more effectively treat people now affected. The National Institute of Neurological Disorders and Stroke (NINDS), a unit of the Federal government's National Institutes of Health (NIH), is the agency with primary responsibility for brain and neuromuscular research. NINDS sponsors research on dystonia both in its facilities at the NIH and through grants to medical centers throughout the country. Scientists working at the National Institute on Deafness and Other Communication Disorders, also part of the NIH, are studying improved treatments for speech and voice disorders associated with dystonias. Support for dystonia research is also provided by privately funded organizations such as the Dystonia Medical Research Foundation.
Scientists at the NINDS laboratories have conducted detailed investigations of the pattern of muscle activity in persons with focal dystonias.
One of the most important characteristics is the failure of reciprocal inhibition, a normal process in which muscles with opposite actions work without opposing each other. In dystonia, the tightening of muscles is associated with an abnormal pattern of muscles fighting each other. Studies at the NINDS have probed the spinal reflex function and found abnormalities consistent with the defect in reciprocal inhibition. Other studies are probing brain activity and its relation to these observations.
The search for the gene or genes responsible for some forms of dominantly inherited dystonias has been narrowed to chromosome 9. The eventual discovery of the actual gene(s) involved should lead to a laboratory test to diagnose primary dystonia, the identification of the abnormal gene product, and the rational development of specific therapies or cures. Scientists are also reviewing data on populations thought to inherit the disease in other ways.
Investigators are asking why the symptoms in primary dystonia vary so widely in type and severity since such patients show no obvious cell degenerations or changes in the basal ganglia. Studies in this area of the brain are complicated by the large number of distinct but interrelated neurochemical systems. Meanwhile, scientists continue their search for therapies that may help treat dystonic symptoms. Investigators are seeking improved methods of administering botulinum toxin and better surgical techniques to treat symptoms.
Where can I get more information?
Five privately supported voluntary health agencies supply information about the dystonias and their own activities and services:
American Speech-Language-Hearing Association
10801 Rockville Pike
Rockville, Maryland 20852
(800)638-8255 (toll free, except Alaska, Hawaii andMaryland)
Benign Essential Blepharospasm Research
P.O. Box 12468
Beaumont, Tx 77726-2468
Dystonia Medical Research Foundation
8383 Wilshire Boulevard, Suite 800
Beverly Hills, California 90210
National Foundation for Jewish Genetic
250 Park Avenue, Suite 1000
New York, New York 10177
National Spasmodic Torticollis Association, Inc.
P.O. Box 873
Royal Oak, Michigan 48068-0873
For further information, contact:
Office of Scientific and Health Reports
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, Maryland 20892
This file was created by scanning NIH Publication No. 91-717