Hemidystonia involves the arm and leg on the same
side of the body.
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.
Genetic studies have revealed an underlying cause in many patients - a
mutation in a gene named DYT1 (see "What research is being
done?"). And it has been discovered that this gene is related not only
to generalized dystonia, but also to some forms of focal dystonia. Note,
however, that most dystonia, of any type, is not due to this gene and has an
unknown cause.
Cervical dystonia, also called 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.
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 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 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, approximately 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 there 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.
- 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. Note that not all of the medications mentioned below
are currently available for patients in the United States.
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. Sometimes
these medications can be sedating, especially at higher doses, and this can
limit their usefulness.
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. Once again, side effects can restrict the use of these
medications.
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 up to 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.
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 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. The National Eye Institute (NEI) supports work on the study
of blepharospasm and related problems (see above) and the National Institute
of Child Health and Human Development (NICHD) supports work on dystonia,
including the rehabilitation aspects of the disorder.
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.
Where can I get more information?
Several privately supported voluntary health agencies
supply information about the dystonias and their own activities and
services:
American Speech Language Hearing Association (ASHA)
10801 Rockville Pike
Rockville, MD 20852-3279
actioncenter@asha.org
http://www.asha.org
Tel: 301-897-5700 800-638-8255
Fax: 301-571-0457
Benign Essential Blepharospasm Research Foundation,
Inc.
637 North 7th Street Suite 102
P.O. Box 12468
Beaumont, TX 77726-2468
bebrf@sbcglobal.net
http://www.blepharospasm.org
Tel: 409-832-0788
Fax: 409-832-0890
Dystonia Medical Research Foundation
1 East Wacker Drive
Suite 2430
Chicago, IL 60601-1905
dystonia@dystonia-foundation.org
http://www.dystonia-foundation.org
Tel: 312-755-0198
Fax: 312-803-0138
National Spasmodic Torticollis Association
9920 Talbert Avenue
Suite 233
Fountain Valley, CA 92708
NSTAmail@aol.com
http://www.torticollis.org
Tel: 714-378-7837 800-HURTFUL (487-8385)
Fax: 714-378-7830
Worldwide Education & Awareness for Movement
Disorders (WE MOVE)
204 West 84th Street
New York, NY 10024
wemove@wemove.org
http://www.wemove.org
Tel: 800-437-MOV2 (6682) 212-875-8312
Fax: 212-875-8389
For information on other neurological disorders or
research programs funded by the National Institute of Neurological Disorders
and Stroke, contact the Institute's Brain Resources and Information Network
(BRAIN) at:
BRAIN
P.O. Box 5801
Bethesda, MD 20824
(800) 352-9424
www.ninds.nih.gov
Source: National Institutes of Health; National Institute of
Neurological Disorders and Stroke - NIH Publication No. 04-717
