When dystonia is present at rest, it is important to examine children
when they are as relaxed as possible. Any stress or discomfort may
worsen the symptoms.
Muscle tone is not necessarily increased in children with dystonia;
however, tone may be increased and the examiner may have difficulty
in differentiating dystonia from spasticity or parkinsonian rigidity.
This determination becomes particularly difficult when dystonia and
spasticity are simultaneously present. This occurs frequently in children
with cerebral palsy. It is equally important to examine for other
movement disorders, such as ataxia or myoclonus, as this may provide
clues to a particular diagnosis.
The timing of dystonia throughout the day is important. Dopa-responsive
dystonia may improve upon awakening in the morning or after a nap;
then the symptoms may become progressively worse throughout the day.
Other forms of dystonia may be worse upon morning awakening. Dystonia
is usually not present during sleep. Continued stiffness of the limbs
during sleep suggests possible spasticity or fixed joint contractures.
There are several genetic causes of dystonia that may have autosomal
dominant inheritance. Therefore, a thorough family history of dystonia or
other neurological diseases is very important. The history of the onset
of dystonia is useful, but occasionally confusing as dystonia may start
many years after the causative event. As always, a toxin exposure or
chronic use of certain medications (particularly neuroleptics and other
psychiatric medications) must be investigated. Such medicines may cause
dystonia even after they have been stopped.
The mechanism of dystonia is one of the most poorly understood issues
in movement disorders. Studies in humans and animals have not been
able to find a good explanation that can relate particular injuries to the
emergence of dystonic symptoms. Dystonia is frequently associated with
injury to the basal ganglia, in particular the sensory-motor regions of the
putamen. In children, dystonia may also occur with decreased dopamine
as occurs in dopa-responsive dystonia (DRD) or in response to dopamine
|Understanding the role of dopamine remains elusive.|
In adults with dystonia, measurement of the cellular activity in
the basal ganglia shows that these cells often respond to
movements of multiple limbs. This suggests that there is confusion
or "cross-talk" between different body parts. It is possible that
this confusion relates to the involuntary activation of normally
suppressed muscles. Human and animal research has shown that
for adult-type focal dystonia, there is also confusion of the cell
responses in cerebral cortex. Therefore, it is possible that
abnormalities in the cortex may be one of causes of dystonia.
Understanding the role of dopamine remains elusive. An abnormally low
level of dopamine causes many childhood dystonias; in parkinsonism, it
is possible to cause dystonic symptoms by administering large amounts
of dopamine. On the other hand, acute dystonic reactions in children
and adults are caused by medications that selectively block the dopamine
receptors in the indirect pathway. These reactions are treated with
anticholinergic medications that may increase the effectiveness of dopamine
in both the direct and indirect pathways.
When muscle activity is recorded using electromyography (EMG) electrodes,
many children and adults with dystonia have a rapid, machine-gun-like,
staccato firing of muscle fibers. These firings are involuntary and completely
unlike the normal patterns of muscle electrical activity. In some cases, similar
rapid repetitive firing has been found in the basal ganglia. On the other
hand, this type of activity is not always found, and, in some cases of dystonia,
the involuntary muscle activity has a pattern that is essentially identical
to normal muscle activation.
Multiple genes for dystonia have been found, causing autosomal dominant
inheritance. These include...
- DYT1 (9q34, encodes torsinA)
DYT5 (14q22.1-2, encodes GTP cyclohydrolase I, leading to
Dopa-responsive dystonia or Segawa's disease)
Cerebral palsy (often with delayed onset), kernicterus, hypoxic injury, head
trauma, encephalitis, tumors, stroke in the basal ganglia (a rare result of
varicella or vascular abnormalities including Moya-Moya disease), congenital
Fahr's disease, neurodegeneration with brain iron accumulation type I (NBIA-I,
formerly known as Hallervorden-Spatz disease, 20p12.3-p13), Huntington's
disease (Westphal variant, IT15-4p16.3), spinocerebellar ataxias (SCAs),
neuronal ceroid lipofuscinoses, Rett syndrome, Tay-Sachs disease, Sandhoff's
disease, Niemann-Pick type C, metachromatic leukodystrophy, striatal necrosis,
Leigh's disease, neuroacanthocytosis, vitamin E deficiency, HARP syndrome
(hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa, and
pallidal degeneration), Pelizaeus-Merzbacher disease, ataxia-telangiectasia
Glutaric aciduria, acyl-CoA dehydrogenase deficiency, aromatic L-amino acid
decarboxylase deficiency, dopa-responsive dystonia or DRD (biopterin
metabolic defect DYT5, or tyrosine hydroxylase deficiency), dopamine agonist
-responsive dystonia (or ALAD: aromatic L-amino acid decarboxylase deficiency),
mitochondrial disorders, Wilson's disease, homocystinuria, GM1 gangliosidosis,
metachromatic leukodystrophy, Lesch-Nyhan disease, Niemann-Pick type C,
methylmalonic aciduria, tyrosinemia
Drug- or Toxin-induced:
(Drug- or toxin-induced dystonia may occur while taking the drug, or months
after stopping the drug.) Neuroleptic and anti-emetic medications (e.g., haloperidol,
thorazine, olanzapine, risperidone, quetiapine, compazine, etc.), calcium
channel blockers, stimulants (e.g., amphetamine, cocaine, ergot alkaloids, etc.),
anticonvulsants (e.g., carbamazepine, phenytoin, etc.), thallium, manganese,
carbon monoxide, ethylene glycol, cyanide, methanol, wasp sting
Paroxysmal kinesogenic choreoathetosis (PKC), paroxysmal non-kinesogenic
choreoathetosis (PNKC), familial periodic paralysis, exercise-induced dystonia,
complex migraine, alternating hemiplegia, paroxysmal torticollis of infancy
Disorders That Mimic Dystonia:
Tonic seizures (including paroxysmal nocturnal dystonia caused by nocturnal
frontal lobe seizures), syringomyelia, Arnold-Chiari malformation type II, atlanto
-axial subluxation, syringomyelia, posterior fossa mass, cervical spine
malformation (including Klippel-Feil syndrome), ocular skew deviation with
vertical diplopia causing neck twisting, juvenile rheumatoid arthritis, Sandifer's
syndrome (gastrointestinal disorder associated with hiatus hernia in infants),
spasmus nutans, tics, self-stimulation, spasticity, myotonia, rigidity, stiff-person
syndrome, Isaac's syndrome, startle disease (hyperexplexia), neuroleptic
malignant syndrome, psychogenic.
The investigation of dystonia depends on the specific type of dystonia. Most
hemidystonia is caused by a localized injury to the brain, often at or before
birth. Therefore, with dystonia that involves one side of the body, a magnetic
resonance image (MRI) of the head usually shows the problem area(s).
|The investigation of dystonia depends on the specific type of dystonia.|
In some cases, an old injury is seen as a region of damaged brain
tissue. In other cases, it appears that one side of the brain is smaller
than the other, presumably due to prior injury and loss of cells.
In many cases, dystonia is without obvious cause and the symptoms
begin before the age of 24 years, and then become progressively
worse. In these cases, there is a genetic mutation in the DYT1 gene.
If no other cause is evident, then the child should be tested for the
presence of this gene, particularly if symptoms began in the foot and
progressed to other areas of the body.
Other genetic tests may be ordered. The tests that are selected are based
on the particular symptoms and whether or not other family members are
affected. It is important to exclude metabolic causes for dystonia, as many
of these diseases are treatable. Dopa-responsive dystonia (DRD) is a rare
disorder of the enzyme pathway responsible for synthesizing dopamine.
DRD is tested by measuring chemicals...
Many neurologists forego testing for DRD and make a diagnosis based on
the rapid resolution of symptoms with very low doses of dopamine. Other
metabolic disorders, such as Wilson's disease, amino acid or organic acid
disorders, and lysosomal storage diseases may be tested for in certain
children. (See section on Etiologies
.) An MRI is often helpful in metabolic
diseases. This imaging technique may show whether or not there is
destruction of part of the brain, a stroke, or a tumor.
Dopa-responsive dystonia (DRD) may cause a variety of motor symptoms
that mimic other disorders. It is now recommended that any child with
unexplained dystonia should receive a trial of L-dopa therapy. If the child
does have DRD, the response is often dramatic and further testing may
be arranged. L-dopa may also be helpful in some children with dystonia
due to cerebral palsy, or perhaps in other metabolic disorders or structural
The most commonly used medication for children with dystonia is trihexyphenidyl
(Artane®). Treatment with trihexyphenidyl often requires very high doses
of 50 mg to -100 mg per day, or even more in some children. If the dose is
raised very slowly, then children seem to tolerate the medicine with relatively
few side effects.
Other medicines that may have some benefit include diazepam (Valium®),
clonazepam (Klonopin®), valproate (Depakote®), baclofen, carbamazepine
(Tegretol®), reserpine, or tetrabenazine (Nitoman®). Choice of the best
regimen is usually by trial and error. It is difficult to predict which medicine
will be most effective for a particular child.
If the dystonia is particularly severe in only a few muscles (as with the focal
dystonias), it may be possible to perform injections of botulinum toxin into
those specific muscles. This toxin weakens the connection between the nerve
and the muscle, thereby weakening the muscle. There is benefit in certain
types of dystonia, with only minimal weakening of the muscle. The goal of
injections of botulinum toxin is to reduce the symptoms of dystonia, without
causing significant muscle weakness.
Toxin injections usually need to be repeated every 3 to 6 months. In younger
children, the procedure may require sedation or anesthesia. There is a long
history of the use of neurosurgical procedures to improve dystonia.
There are reports of considerable success using deep brain stimulation (DBS).
The most successful use of DBS has occurred in children who have a mutation in
the DYT1 gene. Implantation of the stimulator electrode into the globus pallidus
led to gradual resolution of symptoms over 2 to 12 months. In DBS, a
pacemaker is implanted under the skin of the chest or abdomen and a wire
runs from this pacemaker to a small hole in the skull, where it enters the brain.
Pulses from the pacemaker are used to block abnormal activities in the basal
ganglia. Results have been very successful at achieving significant improvement
in children with severe generalized dystonia.
Other neurosurgical procedures for dystonia include cutting muscles or lengthening
tendons to help reduce the effect of the dystonic muscles. There have been
reports that cutting the sensory nerves from muscles where they enter the
spine is helpful; however, this procedure is more likely to improve spasticity,
rather than dystonia.
Kids Move is WE MOVE's Web site devoted to pediatric movement disorders. Healthcare
professionals and parents may access up-to-date information about the recognition,
assessment, treatment, and avenues of support that are available for individuals concerned
with childhood movement disorders.