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Movement disorders (dyskinesias) are disorders associated with abnormal excessive, exaggerated, chaotic, or explosive movements of voluntary muscles. The most common movement disorders in children are hyperkinetic, including tics, chorea, athetosis, dystonia, tremor, and myoclonus. Hypokinetic disorders, which includes parkinsonism, is rare in children.
Cerebral palsy (CP) is a group of permanent movement disorders which are a result of non-progressive lesions or anomalies in the brain. Known risk factors include prematurity, low birth weight, congenital infection, perinatal asphyxia, but in 50% of cases there are no identifiable risk factors. Cerebral palsy can also be acquired, occurring at later ages due to meningitis or head injury. It’s the most common motor disability in children.
The clinical features of cerebral palsy changes over time as the brain develops. Most present with abnormalities during the first 2 years, such as delayed motor milestones, hypotonia, or asymmetry in the two halves of the body. Patients with CP often also have problems with vision, hearing, epilepsy, or cognitive development.
There are multiple types of cerebral palsy, classified according to the type of movement disorder it causes:
- Spastic cerebral palsy – 70% of cases, characterised by spasticity, usually unilateral, due to upper motor neuron lesion
- Dyskinetic cerebral palsy – 10% of cases, characterised by chorea/athetosis/dystonia
- Ataxic cerebral palsy – <5% of cases, due to cerebellar injury
Tics and Tourette syndrome
Tics are rapid, purposeless, involuntary, stereotypes movements which typically involve the face (grimacing), eyes (blinking), or shoulder (shrugging). They may also be vocal, causing grunting or utterance of words, usually obscene words. Tics are the most common hyperkinetic disorder in children.
Tics are often transient, lasting less than 1 year. If tics last longer than 1 year and there are both motor and vocal tics, a diagnosis of Tourette syndrome is made. Tourette syndrome improves during adolescence, and 50% of cases resolve by adulthood.
Chorea and athetosis
Chorea is a hyperkinetic, rapid, unsustained, irregular, purposeless movement. Athetosis is a sort of “slow chorea”. Athetosis can occur in all disorders which cause chorea, often called choreoathetosis.
|Physiologic chorea||Most normal infants make chorea-like movements which resolve by 1 year of age|
|Sydenham chorea||1 – 8 months after acute rheumatic fever|
|Dyskinetic cerebral palsy||Onset < 2 years, problems with vision, hearing, epilepsy, or cognitive development|
Dystonia is characterised by abnormal sustained muscle contractions which cause twisting motions of the neck or tongue. In children this is most commonly due to dyskinetic cerebral palsy or use of antipsychotics or antiemetics.