The clinical impact of precise electrode positioning in STN DBS on three-year outcomes

Few studies have analyzed the clinical impact of subthalamic nucleus (STN) deep brain stimulation (DBS) as a function of the positioning of the inserted electrode. We investigated retrospectively the three-year outcomes in Parkinson's disease (PD) patients following bilateral STN DBS in terms of the electrode positions. Forty-one advanced PD patients were followed up for over three years following bilateral STN DBS. Patients were evaluated with the Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn and Yahr staging, Schwab and England Activities of Daily Living (ADL), and the Short Form-36 Health Survey (SF-36) before surgery and one, two, and three years after surgery. The patients were divided into two groups according to the electrode position based on the fused preoperative MRI and postoperative CT images: group I included patients who had both electrodes in the STN (n=30) while group II included patients who had one of the electrodes in the STN (n=11). The UPDRS, the Hoehn & Yahr staging, the Schwab and England ADL, and the SF-36 scores showed significant improvements with decreased l-dopa equivalent daily doses (LEDDs) in both groups as well as in the group as a whole for up to three years following bilateral STN DBS. However, the off-medication UPDRS total and motor (part III) scores significantly deteriorated with increased LEDDs for patients in group II three years after STN DBS compared to that of the group I patients. We conclude that more accurate electrode positioning in the STN leads to better long-term outcomes in advanced PD patients following DBS.