Parkinsonian symptoms in tardive dyskinesia. A prevalence study.

Of 49 unselected patients with tardive dyskinesia (TD) 28 (57%) exhibited various parkinsonian signs. Isolated tremor was encountered in 11 patients, tremor with hypokinesia and rigidity in 13 patients, and hypokinesia and rigidity alone in 4. Tremor was detected among patients with scorable peripheral signs of TD. Hypokineto-rigidity, with or without tremor, was attributed to high doses of neuroleptics--notably fluphenazine. This study confirmed reports that isolated parkinsonian signs occurring concurrently with TD must be considered a regular phenomenon even when questionable cases (e.g. tremor in lithium-treated patients, action-tremor in the elderly) are disregarded. However, given the 'fragmentation' of the parkinsonian syndrome, often atypical tremor and signs of anosognosia in TD patients, the final diagnosis may necessitate pharmacological testing (discontinuation of neuroleptic medication, administration of anticholinergics).