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[Residual cerebellar ataxia following acute phenytoin intoxication]
1Service de Neurologie, King Fahd National Guard Hospital, Riyad, Arabie Saoudite.
Abstract:
A 30-year-old man was given high doses of phenytoin together with 4 antituberculous drugs for a seizure associated with a probable brain tuberculoma. He developed hepatic toxicity and his serum phenytoin reached the high level of 298 mumol/l (therapeutic range 40-79 mumol/l). All drugs were stopped and the biological parameters returned progressively to normal over the next 15 days. However, he remained with a cerebellar axial syndrome and was still severely ataxic 2 months later. Brain CT and MRI showed mild cerebellar atrophy. This case and the few other published ones, together with some recent experimental data, show that high doses of phenytoin can be toxic to the cerebellar cortical cells. The rarity of similar cases, while millions of epileptics are under phenytoin treatment, would however suggest that individual susceptibility may play a role in this toxicity.
Insights
High doses of phenytoin can cause cerebellar toxicity, leading to severe ataxia. Individual susceptibility may influence this rare side effect in patients undergoing treatment.
Area of Science:
- Neuropharmacology
- Toxicology
Background:
- Phenytoin is a widely used antiepileptic drug.
- Brain tuberculoma is a rare form of tuberculosis affecting the central nervous system.
Observation:
- A patient receiving high-dose phenytoin with antitubercular drugs developed hepatic toxicity and elevated serum phenytoin levels.
- Following drug cessation, liver function normalized, but the patient experienced persistent cerebellar axial syndrome and severe ataxia.
Findings:
- High-dose phenytoin administration was associated with cerebellar cortical cell toxicity.
- Brain imaging revealed mild cerebellar atrophy in the affected patient.
- This toxicity appears rare, suggesting a potential role for individual susceptibility.
Implications:
- Clinicians should be aware of the potential for phenytoin-induced cerebellar toxicity, especially at high doses or in combination with other drugs.
- Further research into the mechanisms of phenytoin neurotoxicity and individual susceptibility factors is warranted.
- This case highlights the importance of monitoring neurological function in patients on long-term, high-dose phenytoin therapy.