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The Rabbit SyndromeTo The Editor:Two cases of "Rabbit Syndrome" are presented by videotape that demonstrate the typical features of this uncommon condition, which was first described by Villeneuve in 1972 (1). These cases and an additional one (not presented here because consent for publication was not obtained) were identified during the course of a prevalence survey of abnormal movement disorders in 149 schizophrenic inpatients chronically treated with antipsychotics. The results of this survey confirmed a previous prevalence estimate of the syndrome of -2% in patients chronically treated with neuroleptics (2).A major point of interest in the cases is the existence of tremors affecting the periorbicularis oris muscle of the lips with a frequency of 4-6 Hz with coexisting tremors of similar frequency in other body areas, including tongue, chin, and extremities. These tremors were present at rest and disappeared with action. Together with the akinesia and rigidity, they suggest that the "Rabbit Syndrome" is one manifestation of drug-induced parkinsonism. In both cases, the parkinsonian tremor and the associated akinesia and rigidity were the only types of abnormal involuntary movements presented by patients. This is in contrast with the third case (whose videotape is not available), who presented with additional choreoathetoid movements in the hands, which is more typical of tardive dyskinesia.Legends to the Videotape SEGMENT 1. A 59-year-old woman with a 36-year history of schizophrenia and cumulative neuroleptic exposure in excess of 25 years, is currently being treated with haloperidol 1.5 mg/day orally and no anticholinergic agents. There is loss of armswing, and her face is almost expressionless. She presents with resting tremors of the lips, tongue, and upper extremities. In addition, there is marked rigidity.SEGMENT 2. A 55-year-old man with a 33-year history of schizophrenia and cumulative neuroleptic exposure of about 25 years, is currently being treated with haloperidol 2 mglday orally and no anticholinergics. The patient presents with pronounced akinesia, loss of armswing, and rigidity. Tremors of the lips coexist with tremors of the tongue, jaw, and hands.We conclude that the "Rabbit Syndrome" represents drug-induced parkinsonian tremors of the lips and chin.