[Cerebellar atrophy and phenytoin poisoning. An MR study]

Phenytoin has been considered a possible cause of cerebellar degeneration, especially after clinical intoxication. Magnetic resonance provides the diagnosis of anatomical structures in the posterior fossa without the limitation of beam hardening artefacts. The aim of this study was to evaluate the relationship of phenytoin medication and cerebellar atrophy in 11 patients with increased serum levels (21.4 micrograms/ml-95.6 micrograms/ml). Five patients had normal cerebellar structures, although three of them had a history of clinical intoxication and all had at least one episode of increased serum level of DPH. The remaining six patients had moderate severe cerebellar atrophy (n = 4) and atrophy of the vermis cerebelli (n = 5). Two of them had never experienced clinical intoxication. There was no correlation between the degree of atrophy and severity of clinical symptoms and evaluation of serum DPH levels (up to four times normal values). There was also no correlation between cerebellar atrophy, duration of epilepsy and frequency of seizures. We conclude that phenytoin overdosage does not necessarily result in cerebellar atrophy and it is unlikely that phenytoin medication was the only cause of cerebellar atrophy in the remaining patients.