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Phenytoin-induced dystonia and choreoathetosis in two retarded epileptic children
Insights
Phenytoin can cause movement disorders like dystonia and choreoathetosis in children, even at therapeutic levels. These adverse effects may be linked to phenytoin
Area of Science:
- Neurology
- Pediatrics
- Clinical Pharmacology
Background:
- Two 8-year-old children with static encephalopathy, mental retardation, ataxia, spasticity, and seizures developed movement disorders.
- The children had a history of seizures following diphtheria-pertussis-tetanus immunization in infancy.
Observation:
- Intermittent and sustained dystonia and choreoathetosis emerged while patients were on phenytoin therapy.
- Phenytoin serum concentrations were within the therapeutic range during the onset of movement disorders.
- Electroencephalogram abnormalities remained unchanged during the observed movement disorders.
Findings:
- Movement disorders, including dystonia and choreoathetosis, were found to be secondary to phenytoin treatment.
- These adverse effects occurred at therapeutic serum concentrations of phenytoin.
- Metabolic abnormalities associated with similar movement disorders were ruled out.
Implications:
- Phenytoin may induce movement disorders by altering neurotransmitters like serotonin and through its anticholinergic properties.
- The severity of movement disorders might be influenced by pre-existing striatal damage.
- This highlights the importance of monitoring for movement disorders in pediatric patients receiving phenytoin.
Abstract:
Similar movement disorders developed in two 8-year-old retarded children while they were receiving phenytoin. Seizures subsequent to a diphtheria-pertussis-tetanus immunization had developed in each child at 1 to 2 months of age. A static encephalopathy ensued, characterized by mental retardation, ataxia, spasticity, and a mixed seizure disorder. Intermittent dystonia and choreoathetosis developed insidiously while serum phenytoin concentrations were in the therapeutic range. Sustained dystonia and choreoatheosis developed 2 hours after an oral provocation with phenytoin. The baseline abnormalities on the electroencephalogram remained unchanged during the choreoathetosis. Recognizable metabolic abnormalities known to be associated with similar movement disorders were excluded. It was concluded from these studies that the movement disorder is secondary to phenytoin and can occur at therapeutic serum concentrations. Phenytoin is a central anticholinergic agent and a central stimulant of serotonin, and may induce movement disorders as a result of altering these neurotransmitters in the brain. The variable expression of these movement disorders may relate to the nature of the preexisting striatal insult.