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Dystonias are a group of neurological 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, or the entire body. These movements can be
as localized as the eyelids or the vocal cords.
Dystonias affect more than 300,000 people in North America, making them the
third most common movement disorder after Parkinson’s disease and tremor. They
affect people from all races and ethnicities. Dystonias are not fatal, but they
are chronic disorders that are often difficult to predict.
Early symptoms of dystonias may include:
- A deterioration in handwriting after writing several lines
- Foot cramps
- A tendency of one foot to pull up or drag after running or walking some
distance
- Involuntary neck turns, especially when tired
- Voice or speech difficulties
In some individuals, symptoms of a dystonia appear in childhood between the
ages of five and 16, usually in the foot or in the hand. 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 restricted to a
particular part of the body.
Dystonias often progress through various stages. Initially, dystonic
movements appear occasionally and 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, which are due to injury or stroke, people often have
abnormal movements of just one side of the body. The movements may begin at the time of
a brain injury or sometime afterward. Symptoms generally do not usually spread
to other parts of the body.
Dystonias can be classified 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.
Within these classifications, there are patterns of dystonia that are defined
as specific syndromes:
Torsion dystonia is a rare, generalized dystonia that may be inherited.
It
usually begins in childhood and becomes progressively worse. It can leave
individuals seriously disabled and confined to a wheelchair.
Cervical dystonia, formerly referred to as spasmodic torticollis, is the
most common of the focal dystonias. In cervical dystonia, 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.
Cervical dystonia 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 cervical dystonia experience a
spontaneous remission, but the remission may not last.
Blepharospasm is the second most common focal dystonia, causing
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 the 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.
Meige's syndrome is a combination of blepharospasm and oromandibular
dystonia, and sometimes spasmodic dysphonia.
Writer's cramp or "task specific focal dystonia" is a dystonia
that affects the muscles of the hand and sometimes the forearm. It 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) is a condition that can be successfully treated with
medications. Typically, DRD begins in childhood or adolescence with progressive
difficulty in walking and, in some cases, spasticity. For patients with a
variant of DRD known as Segawa's dystonia, the symptoms fluctuate during
the day from relative mobility in the morning to increasingly worse disability
in the afternoon and evening, and after exercise.
Causes
Researchers now believe that dystonias may 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. They suspect a flaw in the body's ability to
process a group of chemicals called neurotransmitters, which help cells in the
brain communicate with each other.
It is believed that nearly half of the cases of dystonias can be connected to
a disease or previous injury. These dystonias are called acquired, or secondary,
dystonias. Stroke, trauma, heavy metal or carbon monoxide poisoning, reactions
to certain drugs, or birth injury (especially due to lack of oxygen) have all
been linked to certain forms of dystonia.
Dystonias that do not have a connection to disease or injury are called
primary or idiopathic dystonias. Of the primary dystonias, many cases appear to
be inherited in a dominant manner, meaning only one carrier parent need
contribute the dystonia gene for the disease to occur. Each child would then
have a 50/50 chance of being a carrier. However, a carrier may or may not
develop a dystonia.
Diagnosis and treatment
There is currently no test that confirms the diagnosis of dystonia. As such, the
physician must rely solely on information provided by the patient, as well as a
physical and neurological examination.
No one treatment has been found to be universally effective in treating
dystonias. Instead, physicians use a variety of therapies aimed at reducing or
eliminating muscle spasms and pain.
Medication
Medications taken by mouth for the treatment of dystonia include trihexyphenadyl (and other related medications that reduce muscle spasms) and
baclofen, a muscle relaxer. However, these medications often must be taken at
high doses that many, particularly older individuals, cannot tolerate. In some
cases, baclofen administered directly to the cerebrospinal fluid (a watery
substance that bathes the spinal cord and brain) may be helpful. This is done by
a small, computerized pump that is implanted in the body.
When the dystonia is fairly well restricted to a part of the body,
intramuscular injections of botulinum toxin can be very effective. Botulinum
toxin works by weakening the muscles just enough so as to relieve the symptoms
of dystonia but without causing excessive weakness. This is the same toxin that
causes botulinum food poisoning. However, the doses administered are a small
fraction of what would be necessary to put a person at risk. Botulinum toxin
therapy has significant advantages over medications taken by mouth or in the
spinal fluid because it is associated with far few side effects.
Surgery
Surgeries have been performed for the treatment of dystonia for many years.
In the past, the surgery involved destroying a small part of the brain. A new
surgery, however, permanently implants electrodes into the part of the brain
called the globus pallidus on both sides. These permanent electrodes deliver
small pulses of electricity to the brain. This is known as deep brain
stimulation. Deep brain stimulation is much safer because no part of the brain
is permanently destroyed. Further, deep brain stimulation is much more
effective. For patients with the genetic form of generalized dystonia, the
results of deep brain stimulation have been remarkable. Some patients who were
essentially confined to wheelchairs are now able to walk independently. It is
believed that patients with other forms of dystonia may benefit from deep brain
stimulation as well.
Other treatments
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.
Like many other conditions, education about dystonias and local support
groups can be the greatest tools for managing the disorder and preventing
complications. The following organizations can provide additional information
about dystonias:
Dystonia Medical Research Foundation
One East Wacker Drive, Suite 2430
Chicago, Illinois 60601-1905
(312) 755-0198
www.dystonia-foundation.org
NIH Neurological Institute
P.O. Box 5801
Bethesda, Maryland 20892
(800) 352-9424 or (301) 496-5751
TTY: 301) 468-5981
www.ninds.nih.gov
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