Subthalamic deep brain stimulation: clinical and neuropsychological outcomes in mild cognitive impaired parkinsonian patients

This observational study reports the long-term follow-up of 184 Parkinson's disease (PD) patients treated with subthalamic deep brain stimulation (STN-DBS), retrospectively analyzing the outcomes of subjects with pre-surgical mild cognitive impairment (MCI) compared to those of patients with normal cognition. Patients were divided into PD-MCI or normal cognition groups at baseline, and then compared after 1, 3, 5 and > 5 years of follow-up. Subjects assessed by outpatient clinical follow-up evaluation, not performing a complete clinical and neuropsychological follow-up assessment, were separately considered and rated according to their functional autonomy in daily living activities. The MCI prevalence at baseline was 23 %, increasing to 34 % at 1 year and over 40 % after 3 years. Dementia progressively affected more than 30 % of subjects after a median time of 6 years in the PD-MCI group and 11 years in the normal cognition group (p: 0.028). The mortality risk was slightly higher in PD-MCI patients. Outpatient clinical evaluations showed a progressive increase of subjects completely dependent in the activities of daily living, which ranged from the 11 % at 3 years to 23 % at 5 years and 31 % at > 5 years. MCI can be frequently observed in PD patients, possibly influencing the outcome of surgical therapy. Our findings confirm the sustained long-lasting efficacy of STN-DBS on motor functions in both PD-MCI and normal cognition subjects. PD-MCI patients showed a more precocious cognitive impairment, as expected by natural history studies, but no case of dementia was observed early after surgery.