AMONG PHENYL derivatives with anticonvulsant properties, diphenylhydantoin (phenytoin) was the one which produced the greatest rise in the convulsant threshold for electrical stimuli and, at the same time, had the least hypnotic effect in cats1; prolonged peroral administration was well tolerated.2 On a regimen of 200 to 600 mg daily, 15% of patients developed vertigo, ataxia, tremor, diplopia, and nausea. The symptoms and signs of intoxication disappeared when the dosage was reduced.3
More than 20 years later, Utterback et al4 reported severe cerebellar degeneration in a patient with grand mal, who had been receiving large doses of diphenylhydantoin. Similar changes were found in cats. Since then, others have reported cerebellar degeneration,5-11 and the serum concentration was thought to be related to the pathology.9,11
Among reliable signs of cerebellar degeneration, loss of Purkinje's cells has been reported but not glial proliferation. Other degenerative changes