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.
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 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.
One way to classify the dystonias is according to the parts of the body
they affect:
Generalized dystonia affects most or all of the body.
Focal dystonia is localized to a specific part of the body.
Multifocal dystonia involves two or more unrelated body parts.
Segmental dystonia affects two or more adjacent parts of the
body.
Hemidystonia involves the arm and leg on the same side of the
body. This type of dystonia often results from stroke.
Some patterns of dystonia are defined as specific syndromes:Torsion
dystonia, previously called dystonia musculorum
deformans or DMD, 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 symptoms 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, and musician'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. The diagnosis of DRD may be missed
since it mimics many of the symptoms of cerebral palsy.
Investigators believe that the dystonias result from an abnormality in
an area of the brain called the basal ganglia where some of the messages
that initiate muscle contractions are processed. 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:
- GABA (gamma-aminobutyric acid), an inhibitory substance that
helps the brain maintain muscle control.
- Dopamine, an inhibitory chemical that influences the brain's control
of movement.
- Acetylcholine, an excitatory chemical that helps regulate dopamine in
the brain. In the body, acetylcholine released at nerve endings causes
muscle contraction.
- Norepinephrine and serotonin, inhibitory chemicals that help
the brain regulate acetylcholine.
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 50/50 chance of being a carrier. In
dystonia, however, 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.
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.
No one treatment has been found universally effective. Instead,
physicians use a variety of therapies aimed at reducing or eliminating
muscle spasms and pain.
Medication. Several classes of drugs that may help correct
imbalances in neurotransmitters have been found useful. But response to
drugs varies among patients and even in the same person over time. The
most effective therapy is often individualized, with physicians
prescribing several types of drugs at different doses to treat symptoms
and produce the fewest side effects.
Frequently, the first drug administered belongs to a group that reduces
the level of the neurotransmitter acetylcholine. Drugs in this group
include trihexyphenidyl, benztropine, and procyclidine HCl.
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 effects
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 benefited 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.
Botulinum toxin. Minute amounts of this familiar toxin can be
injected into affected muscles to provide temporary relief of focal
dystonias. First used to treat blepharospasm, such injections have gained
wider acceptance among physicians for treating other focal dystonias. The
toxin stops muscle spasms by blocking release of the excitatory
neurotransmitter acetylcholine. The effect lasts for several months before
the injections have to be repeated.
Surgery and other treatments. Surgery may be recommended for
some patients when medication is unsuccessful or the side effects are too
severe. In selected cases, advanced generalized dystonias have been
helped, at least temporarily, by surgical destruction of parts of the
thalamus, a structure deep in the brain that helps control movement.
Speech disturbance is a special risk accompanying this procedure, since
the thalamus lies near brain structures that help control speech.
Surgically cutting or removing the nerves to the affected muscles has
helped some focal dystonias, including blepharospasm, spasmodic dysphonia
and torticollis. The benefits of these operations, however, can be
short-lived. They also carry the risk of disfigurement, can be
unpredictable, and are irreversible.
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.
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 at
the National Institute on Deafness and Other Communication Disorders
(NIDCD), also part of the NIH, are studying improved treatments for speech
and voice disorders associated with dystonias.
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. Other studies at the NINDS have probed the spinal reflex function
and found abnormalities consistent with the defect in reciprocal
inhibition. Other studies using EEG analysis and neuroimaging 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 continues. In 1989 a team of researchers
mapped a gene for early-onset torsion dystonia to chromosome 9; the gene
was subsequently named DYT1. In 1997 the team sequenced the DYT1 gene and
found that it codes for a previously unknown protein now called "torsin
A." The discovery of the DYT1 gene and the torsin A protein provides the
opportunity for prenatal testing, allows doctors to make a specific
diagnosis in some cases of dystonia, and permits the investigation of
molecular and cellular mechanisms that lead to disease.
The gene for Segawa's dystonia has been found. It codes for an enzyme
important in the brain's manufacture of dopamine.
Keeping on Top of Your Condition
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Seven 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 20852-3279
(301) 897-5700
(800) 638-8255
http://www.asha.org/
Benign Essential Blepharospasm Research Foundation, Inc.
P.O. Box
12468
Beaumont, Texas 77726-2568
(409) 832-0788
http://www.blepharospasm.org/
Dystonia Medical Research Foundation
One East Wacker Drive
Suite
2430
Chicago, Illinois 60601-1905
(312) 755-0198
http://www.dystonia-foundation.org/
National Foundation for Jewish Genetic Diseases, Inc.
250 Park
Avenue, Suite 1000
New York, New York 10177
(212) 371-1030
http://www.nfjgd.org/
National Spasmodic Torticollis Association
9920 Talbert
Avenue
Suite 233
Fountain Valley, California 92708
(800)
487-8385
(714) 378-7837
http://www.torticollis.org/
Tardive Dyskinesia/Tardive Dystonia National Association
4244
University Way, N.E.
P.O. Box 45732
Seattle, Washington
98145-0732
(206) 528-2117
Worldwide Education and Awareness for Movement Disorders (WE
MOVE)
204 W. 84th Street
New York, New York
10024
(212)875-8312
(800) 437-MOV2
Fax: 212-875-8389
Email:
wemove@wemove.org
http://www.wemove.org/
For further information on dystonia research or other neurological
disorders, contact: National Institute of Neurological Disorders and
Stroke
Office of Communications and Public Liaison
PO Box
5801
Bethesda, Maryland 20824
(301)496-5751
(800)352-9424
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