Subthalamic nucleus stimulation does not cause deterioration of preexisting hallucinations in Parkinson's disease patients

Background: Among the neuropsychiatric symptoms in Parkinson's disease (PD) patients, hallucination can result from the disease itself or medical treatment. Hallucination associated with subthalamic nucleus stimulation (STN-DBS) has been reported; however, it is still unclear whether PD patients with a history of hallucination are appropriate candidates for STN-DBS or not. Aims: We investigated the effect of STN-DBS on preexisting hallucination associated with advanced PD. Methods: Eighteen STN-DBS patients were investigated retrospectively. The severity of hallucination was assessed by the thought disorder score on the Unified Parkinson's Disease Rating Scale (UPDRS, part 1-item 2) in the patients' interviews; the score 6 months after the initiation of STN-DBS was compared with the highest score throughout the preoperative history and the score 2 weeks before surgery. Results: Hoehn-Yahr stage and motor score (UPDRS part 3) were significantly improved following STN-DBS. Six months after the initiation of STN-DBS, the severity of hallucination, assessed by thought disorder score, did not increase, but rather decreased compared with the preoperative level (p < 0.05 by McNemar's test). The daily levodopa equivalent dose was increased in 2 patients without the development of hallucination. On the other hand, anti-parkinsonian drugs were totally withdrawn in 1 patient, but without improvement of hallucination. Conclusions: Our findings indicate that STN-DBS surgery does not always lead to deterioration of preexisting hallucination in PD. In advanced PD, hallucination involves a multifactorial pathogenesis and a history of hallucination is not a contraindication to STN-DBS surgery.