Parkinson's disease-related visual hallucinations unresponsive to atypical antipsychotics treated with cholinesterase inhibitors: a case series.

I report here clinical effects of cholinesterase inhibitors (rivastigmine and donepezil) on visual hallucinations emerging in the course of Parkinson's disease (PD) and clinically unresponsive to antipsychotics. Five patients with PD (with or without dementia) complicated by visual hallucinations and unresponsive to atypical antipsychotics were offered a 12-week, open-label trial of a cholinesterase inhibitor. All 5 subjects completed the trial with no major adverse effects and, of note, no discontinuations due to adverse events. Visual hallucinations resolved in 4 subjects and were markedly diminished in one person. Neither changes in UPDRS scores nor exaggeration of subjective complaints about extrapyramidal symptoms were noted during treatment. Cholinesterase inhibitors might represent a useful alternative to antipsychotics for patients with PD accompanied by visual hallucinations even in the absence of dementia. One must, however, not forget that their use with this indication remains experimental and safety measures as well as accurate clinical surveillance are of crucial importance.