Abstract: | Transient hyperkinesia was observed in a 16-year-old epileptic and mentally retarded patient after a single intravenous perfusion of diphenylhydantoin (DPH). No clinical signs of DPH intoxication were associated with the movement disorder. Repeated plasma anticonvulsant level determinations never showed toxic concentrations of DPH. Since a few spontaneous episodes of hyperkinesia had been observed before, the DPH intravenous perfusion could have unmasked a preexisting latent movement disorder in our patient. However, neuroradiological investigations failed to demonstrate the existence of any anatomical damage of the basal ganglia, and HVA as well as 5-HIAA levels measured in the CSF with the probenecid technique were within the normal range 2 months after cessation of hyperkinesia. HVA and 5-HIAA levels have also been measured in the CSF during the period with hyperkinesia; the results are discussed with reference to previously published data concerning cerebral monoamine metabolism in drug-treated epileptic patients. |