Exclusion criteria comprised patients with atypical Parkinsonian syndromes or any alternative cause of parkinsonism. sufficient German language skills were present. a stable postoperative condition was ensured (approximately 6 months postoperatively) and 4. bilateral DBS electrodes were implanted in the STN either under local or general anesthesia with microelectrode recordings for optimized targeting 3. Parkinson´s disease in Hoehn & Yahr 2–3 was present 2. Patients required a significant improvement of the motor-subscore of the Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS III) after intake of immediate-release soluble levodopa. Preoperatively, all PD patients were screened and selected in accordance to international guidelines of DBS surgery (CAPSIT protocol). the preoperative MoCA can predict changes in quality of life (QoL). the MoCA is a favourable perioperative, cognitive screening test to identify patient’s cognitive status, as frontal executive dysfunction is better addressed in shorter application time 2. To date, the MoCA has not been established as a standard tool in the preoperative DBS evaluation procedure. The test has been shown to be more sensitive with equivalent specificity compared to the MDRS in a general PD patient population. The MoCA has become a popular cognitive screening instrument in PD addressing particular frontal and executive functioning. Thus, STN-DBS tends to impair specific cognitive subdomains, which are not adequately measured by the total score of the MDRS. However, further specified neuropsychological tests showed an impairment of executive functions as decline of verbal fluency and worsened attentional inhibition of automated reactions in PD patients with STN-DBS. Multicenter, randomised, controlled trials revealed no change of global cognitive function in the DBS-group postoperatively compared to PD patients in the non-surgical group as revealed by an unchanged total score of the MDRS. The MDRS is recommended by the Movement disorder society (MDS) to detect mild cognitive impairment (MCI) in Parkinson’s disease. One of the most often used screening tests represents the Mattis Dementia Rating Scale (MDRS). Recurrent findings are unchanged total scores of screening tests assessing global cognitive function in PD patients with STN-DBS, but deterioration of specific cognitive subdomains. Studies on cognitive performances in STN-DBS operated PD patients revealed heterogeneous results. One important aspect in the decision process represents the patient´s cognitive profile and the risk to develop postoperative cognitive decline, since new postoperative onset of cognitive disturbances due to STN-DBS affects activities of daily living and psychiatric function. The current recommendations for appropriate, preoperative patient screening comprise the assessment of the overall health condition, age, comorbidities, neuropsychiatric profile, the severity and L-dopa responsiveness of the different motor symptoms and motor fluctuations. Careful patient selection is an essential determinant of consistent, favourable, postoperative outcomes after DBS surgery, since about one third of DBS failures could be attributed to inappropriate patient selection in past studies highlighting the need for careful preoperative evaluation. In Parkinson´s disease (PD), deep brain stimulation (DBS) of the subthalamic nucleus (STN) has emerged as an effective, established therapy in specific patients in advanced stages of the disease. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Pötter-Nerger received lecture fees from Abbott and Licher, and served as consultant for Medtronic, Boston scientific, Abbott and Abbvie. Gerloff reports honoraria from Bayer Healthcare, Boehringer Ingelheim, Acticor Biotech, Sanofi Aventis Amgene, and Prediction Bioscience. Koeppen reported no financial disclosures. Hamel received lecture fees and honoraria for serving on advisory boards and travel grants from Boston Scientific, Medtronic, and Abbott. Moll served as medico-scientific consultant to Abbott. Gulberti received travel reimbursements from Medtronic. Schaper reported no financial disclosures. Buhmann served on the scientific advisory boards for Bial and Zambon and received honoraria for lectures from Abbvie, Bial, GE Healthcare, Grünenthal, TAD and UCB. Zittel received research support from Merz Pharmeceuticals and honoraria from Brainlab AG. U.Hidding reported no financial disclosures. Vetorazzi reported no fincancial disclosures. Kirsten received travel and attendance grants from Abbott and Abbvie. Alsalem reported no financial disclosures. Gülke received travel and attendance grants from Abbvie, Abbott, Medtronic and Bial. Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: E.

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