Effect of deep brain stimulation on impulse control behaviors of Parkinson's disease patients: A systematic review and meta-analysis

Parkinson's disease (PD) is a progressive degenerative disorder involving dopaminergic neurons in the substantia nigra. Besides impairment in motor activities, PD patients develop various neuropsychiatric, cognitive, and autonomic problems. Impulse control disorder (ICD) is one of the neuropsychiatric presentations of PD and is characterized by pathological repetition of daily "hedonic" activities including compulsive gambling, eating, shopping, and sexual behavior. The effect of DBS on ICD in PD is controversial; therefore, a comprehensive search was done using the words "Deep brain stimulation", "Impulse control disease, and "Parkinson's disease" in PubMed, Web of Science, and Scopus to answer whether DBS improves ICD in these patients or not. Totally 392 articles were included and after screening and deleting the duplicates, 3 articles were used for meta-analysis using QUIP-RS score. These three studies included 64, 38 and 16 patients. Quality assessment was determined using NIH tool for before and after the studies. The synthesized data suggested that the score of QUIP-RS decreased after surgery -compared to pre-operation status- in favor of symptoms improvement (CI -0.587 to -0.038). We conclude that DBS is a beneficial treatment in PD that reduces the ICD symptoms in midterm period, but more long-term studies are needed to confirm this effect. Lack of RCT, short follow up, and lack of any report on the subscales of QUIP were the major limitations in the included studies.