The malignant course of "benign hallucinations" in Parkinson disease.

OBJECTIVE To monitor progression of "benign hallucinations" in Parkinson disease (PD). METHODS We searched our data repository for subjects with PD with 3 sets of neuropsychological testing during 3 years and Unified Parkinson's Disease Rating Scale thought disorder scores taken at 4- to 12-month intervals during this period. We found 48 patients with benign hallucinations, defined as a thought disorder score of 2 (benign hallucinations, insight retained), receiving no treatment for hallucinations. We followed up thought disorder scores under best medical management for at least 3 years or until a thought disorder score of 3 (loss of insight) or 4 (delusions) occurred. In subjects whose thought disorder scores remained at 2, we assessed neuroleptic use and decreases in PD medications to abate hallucinations. RESULTS Most subjects (81%) progressed to thought disorder scores of 3 or 4. In 7 (78%) of 9 subjects who retained a thought disorder score of 2, PD medications were reduced to treat hallucinations, and 3 subjects (33%) also received neuroleptics. If the composite end point (any of the criteria) was used, 96% of subjects progressed, with only 2 subjects continuing with stable, untreated benign hallucinations. CONCLUSIONS Because hallucinations progress, the concept of benign hallucinations is prognostically misleading. Though hallucinations with retained insight may be "benign" for the moment, they portend serious consequences. The term benign hallucinations of PD should be considered generally unsound and dropped from operative vocabulary.