The effects of apomorphine on visual perception in patients with Parkinson disease and visual hallucinations: a pilot study.

Visual hallucinations (VHs) often occur in patients with advanced Parkinson disease (PD). Overstimulation of dopamine receptors has been considered as one of the causes for VHs in PD. However, several clinical studies suggested that apomorphine infusion did not worsen existing VHs in PD, but could even improve VHs in some PD patients. This pilot study included 4 PD patients with VHs, who were examined before, during, and after an intravenous infusion with apomorphine. The examinations included tests for lower- and higher-order visual functions, attention, and motor functions. Apomorphine had a significantly positive effect on contrast sensitivity and showed a significantly negative effect on attention. These results may explain why apomorphine is able to improve VHs in PD in some patients with mainly visual perceptive problems, but may also worsen VHs in other patients because of impaired attention.