Motor outcome and electrode location in deep brain stimulation in Parkinson's disease

OBJECTIVES: To evaluate the efficacy and adverse effects of subthalamic deep brain stimulation (STN‐DBS) in patients with advanced Parkinson's disease (PD) and the possible correlation between electrode location and clinical outcome. METHODS: We retrospectively reviewed 87 PD‐related STN‐DBS operations at Helsinki University Hospital (HUH) from 2007 to 2014. The changes of Unified Parkinson's Disease Rating Scale (UPDRS) part III score, Hoehn & Yahr stage, antiparkinson medication, and adverse effects were studied. We estimated the active electrode location in three different coordinate systems: direct visual analysis of MRI correlated to brain atlas, location in relation to the nucleus borders and location in relation to the midcommisural point. RESULTS: At 6 months after operation, both levodopa equivalent doses (LEDs; 35%, Wilcoxon signed‐rank test = 0.000) and UPDRS part III scores significantly decreased (38%, Wilcoxon signed‐rank test = 0.000). Four patients (5%) suffered from moderate DBS‐related dysarthria. The generator and electrodes had to be removed in one patient due to infection (1%). Electrode coordinates in the three coordinate systems correlated well with each other. On the left side, more ventral location of the active contact was associated with greater LED decrease. CONCLUSIONS: STN‐DBS improves motor function and enables the reduction in antiparkinson medication with an acceptable adverse effect profile. More ventral location of the active contact may allow stronger LED reduction. Further research on the correlation between contact location, clinical outcome, and LED reduction is warranted.