The effect of methylphenidate on tardive dyskinesia

• 1.

  1. The effect of methylphenidate on motor activity was studied on chronic schizophrenics with a history of two or more years of neuroleptic treatment.

• 2.

  2. Clinical examination and polygraphic recording - (EEG, EOG and multichannel EMG) were carried out on 41 patients. Of these, 15 had tardive dyskinesia, 11 had minor dyskinetic phenomena and 15 had no clinical signs of hyperkinetic motor disorder.

• 3.

  3. A distinct qualitative pattern of motor activity was observed in TD patients as pseudorhythmic bursts of muscle action potentials which appeared in varying muscle groups at the rate of 0.6 - 1.2/second. These bursts of muscle activity were not found in the non-TD group of patients.

• 4.

  4. Ritalin administration had a marked effect on TD patients as observed by the increased amplitude, duration and distribution of pseudorhythmic bursts. Eight out of 11 patients, with minor dyskinetic manifestations responded to methylphenidate with the same pattern as TD.

• 5.

  5. Methylphenidate was found to evoke and enhance abnormal muscle activity in patients whose extrapyramidal motor system is already affected by neuroleptics. These findings suggest that methylphenidate administration, in combination with polygraphic recordings, may be a useful tool in the early diagnosis of TD.