Instrumental assessment of lingual motor instability in tardive dyskinesia.

Instrumental measurement of fine tongue instability was carried out in 28 psychiatric patients (13 with and 15 without tardive dyskinesia [TD]) and 11 normal controls. All of the 13 TD patients and 4 of the 15 non-TD patients had instability of tongue greater than 2 standard deviations of the normal control mean. The tongue instability correlated with lingual (but not total body) dyskinesia rating and with age in the psychiatric patients. Our findings suggest that spectral analysis of fine tongue position is sensitive to overt as well as subclinical dyskinesia associated with neuroleptic usage.