Faculty Bibliography

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

OBJECTIVE: To evaluate whether subthalamic nucleus (STN) stimulation has an effect on the orthostatic regulation of patients with Parkinson disease (PD), we studied cardiovascular regulation during on and off phases of STN stimulation. METHODS: We examined 14 patients with PD (mean age 58.1 +/- 5.8 years, 4 women, 10 men) with bilateral STN stimulators. Patients underwent 3 minutes of head-up tilt (HUT) testing during STN stimulation and after 90 minutes interruption of stimulation. We monitored arterial blood pressure (BP), RR intervals (RRI), respiration, and skin blood flow (SBF). Baroreflex sensitivity (BRS) was assessed as the square root of the ratio of low-frequency power of RRI to the low-frequency power of systolic BP for coherences above 0.5. RESULTS: During the on phase of the STN stimulation, HUT induced no BP decrease, a significant tachycardia, and a significant decrease of SBF. During the off phase of stimulation, HUT resulted in significant decreases in BPsys and RRI and only a slight SBF decrease. HUT induced no change of BRS during stimulation, but lowered BRS when the stimulator was off (p < 0.05). CONCLUSIONS: STN stimulation of patients with PD increases peripheral vasoconstriction and BRS and stabilizes BP, thereby improving postural hypotension in patients with PD. The results indicate that STN stimulation not only alleviates motor deficits but also influences autonomic regulation in patients with PD

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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

The cognitive effects of subthalamic nucleus (STN) stimulation in Parkinson's disease (PD) have been examined. However, there are no reported studies that evaluate, by incorporating a disease control group, whether neuropsychological performance in surgical patients changes beyond the variability of the assessment measures. To examine this issue, 17 PD patients were tested before and after bilateral STN stimulator implantation, both on and off stimulation. Eleven matched PD controls were administered the same repeatable neuropsychological test battery twice. Relative to changes seen in the controls, the surgery for electrode placement mildly adversely affected attention and language functions. STN stimulation, per se, had little effect on cognition. The STN DBS procedure as a whole resulted in a mild decline in delayed verbal recall and language functions. There were no surgery, stimulation, or procedure effects on depression scale scores. In contrast to these group findings, one DBS patient demonstrated significant cognitive decline following surgery

Awareness that SCI pain is common emerged during the past decade. However, there are a number of unresolved issues. There is a need for variety of experimental models to reflect diversity of SCI pains. Current classification is not as user-friendly as it should be. More attention should be given to a condition of the spinal cord below and above the SCI lesion. A consensus for what is an optimal SCI functional assessment for patients with sensory complaints and pain should be developed. Further extensive SCI pain research is needed prior to spinal cord regeneration trials in order to be able to cope with a potential for newly developed pains that may appear during incomplete spinal cord regenerative attempts