Chronic electrical stimulation of the subthalamic nucleus (STN) has been shown to be safe and effective in the treatment of medically refractory idiopathic Parkinson's disease. The clinically most ...relevant location of stimulation within the physiologically defined STN has not been confirmed. We reviewed the locations of active electrical contacts in 33 patients who underwent simultaneous bilateral STN deep brain stimulator (DBS) implantation.
The location of the microelectrode-defined dorsal STN border was compared to the location of the center of the active contact(s) employed in achieving optimal clinical results 6 to 18 months postoperatively. Furthermore, the location of this optimal contact was determined with respect to each individual patient's midcommissural point. Bilateral monopolar stimulation was employed in 30 patients using quadripolar DBS electrodes.
After a minimum follow-up period of 6 months, the motor subscores (UPDRS Part III) in the postoperative on-stimulation/off-medication state were 64 ± 18% (mean ± SD) improved as compared to the preoperative off-medication state (
p < 0.01). Additionally, an improvement of 53 ± 38% was noted when comparing the postoperative on-stimulation/on-medication state to the preoperative on-medication state (
p < 0.01). On average, the center of the optimal contact was 13.3 mm lateral, 0.5 mm posterior, 0.1 mm inferior to the mid-commissural point and was 0.1 ± 2.1 mm dorsal to the physiologically defined dorsal STN border.
While the achieved clinical results are comparable to those published in the literature, it appears that monopolar electrical stimulation at the anterior dorsolateral border of the STN yields optimal clinical results. Further studies are crucial in determining the precise mechanism of various modes of DBS in an effort to maximize clinical outcome.
Transcranial electrical stimulation with myogenic motor evoked potential (MEP) recording was used for intraoperative neurophysiologic monitoring in 341 consecutive "high-risk" neurosurgical or ...orthopedic procedures. Overall, the success rate for establishing reliable MEP response was 94.8% for upper extremities and 66.6% for lower extremities. The rate was only 39.1% for lower extremities in patients with preoperative motor deficit and up to 81% in neurologically intact adults. Further analysis demonstrated that extremes of age or the presence of a lesion in the spinal cord and motor deficit contributed to failure in obtaining reliable MEPs.
