Cogwheel rigidity related to lithium maintenance.

Neurological examinations of 27 outpatients receiving lithium carbonate maintenance therapy for recurrent affective illness revealed that most of the patients receiving lithium for more than 8 months had cogwheel rigidity. The data suggest a positive correlation between the duration of lithium maintenance and the severity of cogwheeling. Intravenous administration of benztropine, an antiparkinsonian drug, did not abolish or significantly ameliorate this symptom.