Chorea
From Holoprosencephaly
What is Chorea?
Chorea is an abnormal voluntary movement disorder, one of a group of neurological disorders called dyskinesias, which are caused by overactivity of the neurotransmitter dopamine in the areas of the brain that control movement. Chorea is characterized by brief, irregular contractions that are not repetitive or rhythmic, but appear to flow from one muscle to the next. Chorea often occurs with athetosis, which adds twisting and writhing movements.
Choreoathetosis is a movement of intermediate speed, between the quick, flitting movements of chorea and the slower, writhing movements of athetosis. Ballism is a violent flinging of one or more limbs out from the body. Choreoathetosis is the most common form in children.
These disorders may affect the hands, feet, trunk, neck, and face. In the face, they often lead to nose wrinkling, continual flitting eye movements, and mouth or tongue movements. These disorders may be distinguished from tics, as tics tend to repeat the same set of movements. In addition, the child often describes a "build-up" in the need to make the tic, with a sense of release afterwards. There is no such sense of release following chorea; the movements are continually changing and flowing from one body part to another.
Examination
Mild chorea may be difficult to distinguish from normal restlessness. Therefore, it is important to assess whether the movements are controllable by the child and whether these movements are sustained or occur only in the doctor's office. It is important to note which parts of the body are involved. The speed and size of the movements determine whether this is most appropriately called chorea, athetosis, choreoathetosis, or ballism. For practical purposes, the distinction is often difficult to make; this distinction is not usually helpful in diagnosis and treatment.
The effect of purposeful movements, such as reaching, speaking, or walking, must be assessed. Dystonia may cause excessive and apparently random movements. These movements are usually worsened with intentional, attempted movements and improve when the child is at rest. There is no image of restlessness, although, in some cases of chorea, the symptoms may appear to be similar. Ataxia may lead to an abnormal gait, with extra movements needed to compensate; however, the movements disappear when the child is steadied or seated.
The timing of the chorea is important. There are paroxysmal types that only occur with sudden movement, exercise, or when the child is under stress. The age of onset is also important. In particular, mild chorea may be normal during the first few years of life, as long as it is not worsening over time. It is important to determine whether there are particular foods that trigger the symptoms, or whether there are clues to a metabolic disorder. These clues include intolerance of certain foods or episodes of unexplained vomiting and lethargy.
Mechanism
Chorea is thought to be caused by damage to the basal ganglia. Chorea can also be induced by drugs (levodopa, anti-convulsants, and anti-psychotics) metabolic and endocrine disorders, and vascular incidents.
Treatment
Chorea may be difficult to treat. If the child is taking any medications that can cause or worsen chorea, these should be tapered and discontinued, if possible. The mainstay of treatment in adults is the class of neuroleptics, including haloperidol and pimozide.
These drugs selectively enhance the function of the indirect pathway by blocking the inhibitory effect of dopamine on this pathway. However, the incidence of side effects in children from neuroleptics has been reported to be as high as 20%. Therefore, it is often safer to start with an alternative medication, such as a benzodiazepine, particularly clonazepam, diazepam, or clobazam. According to reports, certain anti-epileptic medications, such as valproate and piracetam, may improve the symptoms of chorea. In particular, valproate may be very helpful in children with Sydenham's chorea.
What is the prognosis?
The prognosis for individuals with chorea varies depending on the type of chorea and the associated disease.
To learn more about movement problems and treatment options in children with Holoprosencephaly, also see:
[Do all children with HPE have movement problems?]
[How will I know if my child has Dystonia?]
You may also find this external link beneficial:Brain Connection
It describes what areas of the brain control muscle tone and movement.
References
http://www.ninds.nih.gov/disorders/chorea/chorea.htm http://endoflifecare.tripod.com/juvenilehuntingtonsdisease/id61.html
