Objective: To assess the immediate effects of deep brain stimulation of the subthalamic nucleus (STN-DBS) on nonmotor symptoms (NMS) in Parkinson's disease (PD).

Background: Immediate effects of STN-DBS on motor functions are well accepted, but similar data on NMS are mainly lacking.

Methods: 34 PD patients who received bilateral STN-DBS were examined in medication Off state for frequency and severity of 10 NMS (dysphagia, anxiety, depression, fatigue, excessive sweating, inner restlessness, pain, concentration/attention, dizziness, bladder urgency) using a visual analogue scale (VAS) with STN-DBS Off and On. Motor assessments were done using UPDRS part III.

Results: Independent of STN-DBS status, most frequent NMS was fatigue (85% of patients), followed by problems with concentration/attention (71%) and inner restlessness (53%). Frequencies of most NMS were similar in both STN-DBS statuses, while only inner restlessness was significantly decreased by STN-DBS. Severities of most NMS were significantly improved by STN-DBS on the cohort level, while only excessive sweating, pain and dizziness did not show significant severity changes. However, variable proportions of patients (15-71%, depending on the NMS) reported relevant improvements (>10% on VAS) by STN-DBS with fatigue showing the largest proportion of patients with symptom improvement (71%). There were no correlations of severity changes of NMS with motor improvement, demographic data and medication.

Conclusion: STN-DBS does not have major immediate effects on frequencies of NMS, but improves most NMS particularly psychiatric symptoms such as depression, anxiety and fatigue in a variable subset of patients. There is no indication that STN-DBS worsens NMS.