Motor and non motor effects during intraoperative subthalamic stimulation for Parkinson’s disease

Spatial distribution of the clinical effects induced by deep brain stimulation during the intraoperative investigation of the subthalamic nucleus (STN) for Parkinson’s disease (PD) was analysed in 17 patients under local anesthesia. The stimulation parameters were 130 hertz, 100 µs, and voltage ranged from 0.05 to 5 volts. Optimal motor response was assessed as the total and lasting disappearance of wrist rigidity on the side opposite to stimulation.Among the adverse effects induced by stimulation, special attention was given to frequently observed autonomic effects (AE). Full motor response was achieved in 49.2% of the 301 points evaluated,with a mean voltage (MV) of 0.94 volts; paresthesiae occurred in 6.6% (MV: 2 volts), dystonia in 10.6% (MV: 3.4 volts), autonomic effects in 19.6% (MV: 3.1 volts) and oculomotor effects in 31.6% (MV: 3 volts). The motor target was located in the posterodorsal part of the nucleus and the optimal point for motor response was close to the superior limit of the nucleus. Whereas other adverse effects occurred relatively far from the motor target, AE occurred with statistic significance near this point. Their neural substrates, such as limbic system and their relationship with postoperative behavioral disorders, are discussed.