Movement disorders or dyskinesias are a diverse group of entities associated with abnormal excessive, exaggerated, chaotic, or explosive movements of voluntary muscles. They are generally the result of abnormalities of the extrapyramidal system orthe basal ganglia. Movement disorders in children are typicallyhyperkinetic (increased movement) patterns. The abnormalmovements are activated by stress and fatigue and often disappear in sleep. They are typically diffuse and migratory (chorea)but may be isolated to specific muscle groups (segmental myoclonus, palatal myoclonus) and may not disappear in sleep.
Chorea is a hyperkinetic, rapid, unsustained, irregular, purposeless movement that seems to flow from one body part to another. Affected patients demonstrate difficulty keeping the tongue protruded or maintaining grip (milkmaid grip).Patients often attempt to incorporate the involuntary movements into more purposeful movements, making them appear fidgety. Choreiform movement abnormalities may be autoimmune/parainfectious, infectious, genetic, structural, metabolic or toxic in origin (Table 183-2). The movements may occur
Autoimmune/parainfectious (acute rheumatic fever,* systemic lupus erythematosus) Infectious (human immunodeficiency virus, neurosyphilis, scarlet fever, encephalitis) Genetic (Huntington disease, ataxia-telangiectasia) Structural (stroke, neoplasm) Metabolic/toxic (hepatic/renal failure, hyperthyroidism) Drug induced
Physiologic* Essential tremor* Hereditary, degenerative (Huntington disease, Wilson disease) Stroke Metabolic (hyperthyroidism, hepatic encephalopathy, electrolyte disturbances) Drugs/toxins* (caffeine, bronchodilators, amphetamines, tricyclic antidepressants) Psychogenic tremor alone or as part of a more extensive neurologic disorder (e.g., Sydenham chorea, Huntington chorea, systemic lupus erythematosus, or encephalitis).
Athetosis is a hyperkinetic, slow, coarse, writhing movement that is more pronounced in distal muscles. Athetosis is seen frequently in combination with chorea (choreoathetosis) and usually is present in conjunction with other neurologic signs. It may be seen in virtually all the disorders mentioned for chorea. Many children with mixed forms of cerebral palsy have spasticity and choreoathetosis.
Dystonia is characterized by abnormally sustained muscle contraction, causing twisting motion (torsion spasm) and repetitive movements or abnormal postures. Cerebral palsy is the most common cause of dystonia among children, usually associated with basal ganglia or thalamic lesions. Many genetic mutations have been implicated in primary dystonias. Antipsychotics and antiemetics can produce acute dystonic reactions, typically involving the face and neck with torticollis, retrocollis, tongue protrusions, and oculogyric crises (eye rotation). Tardive dyskinesia usually is associated with chronic antipsychotic drug use and presents with characteristic face involvement (tongue thrusting, chewing).
Tremor is a hyperkinetic, rhythmic, oscillatory movement caused by simultaneous contractions of antagonistic muscles. The amplitude and frequency are regular. Inchildren, tremor is usually due to a physiologic tremor,or essential tremor. Essential tremor is the most common movement disorder in adults, and half report onset inchildhood. Other causes of tremor include thyrotoxicosis,hypoglycemia, or drugs (caffeine, bronchodilators, amphetamines, tricyclic antidepressants).