Distinguishing acute and tardive akathisia by monitoring microvibration: a pilot study

One acute and one tardive akathisia patients, respectively, and 10 neuroleptic-treated schizophrenic patients were injected with biperiden 5 mg or saline and the response to anticholinergics was monitored by microvibration (MV) as an indicator of muscle tonus. These data were subjected to the Fast Fourier Transform and an averaged power spectrum was computed. The biperiden injection markedly reduced the power spectral values of MV in acute akathisia. In contrast with acute akathisia, the biperiden injection significantly increased the power spectral values of MV in tardive akathisia. The subjective feelings of akathisia patients were parallel to the power spectral values of MV. Control patients were not affected by such treatment. The present findings show that the subjective symptoms of akathisia can be well defined by the objective, differential response to anticholinergics in a manner similar to the visible extrapyramidal symptoms (dystonia, dyskinesia) induced by neuroleptics.