gms | German Medical Science

Objective: Intraoperative clinical testing is established in STN-DBS to determine final electrode location requiring awake surgery. The aim of this ongoing project is to evaluate whether stimulation-induced therapeutic and side effects of the definite electrode are predictable by intraoperative test-stimulation.

Method: 59 PD-patients receiving bilateral STN-DBS were clinically examined with stepwise increased monopolar stimulation during surgery and DBS programming at matched stimulation depths. Thresholds of therapeutic effects on rigidity, tremor, akinesia as well as threshold and categories of side effects as dysarthria, paraesthesia, oculomotor dysfunction, autonomic and capsular effects were obtained retrospectively from standardized examination protocols. Effects were also analyzed according to the finally chosen trajectory.

Results: Stimulation via permanent electrode caused no side effect at a significantly lower threshold than predicted during intraoperative testing (p<0,001), whereas sufficient therapeutic effects were achieved at significantly higher thresholds. The category of side effects differed frequently, capsular effects were most consistent. Postoperative DBS programming resulted in a satisfactory therapeutic window for monopolar stimulation in 87.96% of STN sides.

Conclusions: The central trajectory was chosen in only 48.3% which emphasizes the impact of MER and intraoperative clinical testing on final electrode location. But stimulation-induced side effects are not predictable by intraoperative testing concerning their thresholds and even their categories. Furthermore intraoperative testing may lead to overestimation of the therapeutic window. In this way our data may stimulate the controversy about awake DBS-surgery.