Object. The authors conducted a study to evaluate repetitive transcranial electrical stimulation (TES) to assess spinal cord motor tract function in individuals undergoing spine surgery, with emphasis on safety and efficacy. Methods. Somatosensory evoked potentials (SSEPs) were elicited using standard technique. Muscle electromyographic values were measured in response to a three- or four-pulse train of stimulation delivered to the motor cortex via subdermal electrodes. They also evaluated whether changes in the minimum stimulus intensity (that is, threshold level) needed to elicit a response from a given muscle predict motor status immediately postoperatively, as well as whether changes in SSEP response amplitude and latency predict sensory status immediately postoperatively. Anesthesia was routinely induced with intravenous propofol and remifentanil, supplemented with inhaled nitrous oxide. Use of neuromuscular block was avoided after intubation. Satisfactory monitoring of muscle response to threshold-level repetitive TES was achieved in all but nine of the 194 patients studied. In contrast, cortical SSEP responses could not be elicited in 42 of 194 individuals. In cases in which responses were present, TES-based evoked responses proved to be extremely accurate for predicting postoperative motor status. Somatosensory evoked potential monitoring was nearly as accurate for predicting postoperative sensory status. There were frequent instances of postoperative motor or sensory deficit that were not predicted by SSEP- and TES-based monitoring, respectively. There were no adverse events attributable to TES-based monitoring, although since this study ended we have had a single adverse event attributable to threshold-level repetitive TES. Conclusions. Intraoperative threshold-level repetitive TES—based monitoring of central motor conduction has proven to be a simple, safe, and highly accurate technique for the prevention or minimization of inadvertent motor deficit during surgery involving the spine or spinal cord.

Electrical stimulation of the vagus nerve has shown efficacy in controlling seizures in experimental models, and early clinical trials have suggested possible benefit in humans. Eleven patients with complex partial seizures were subjected to implantation of vagus nerve stimulators. Electrode contacts embedded in silicone rubber spirals were placed on the left vagus nerve in the low cervical area. A transcutaneously programmable stimulator module was placed in an infraclavicular subcutaneous pocket and connected to the electrode. One patient required replacement of the system due to electrode fracture. Another patient developed delayed ipsilateral vocal-cord paralysis; the technique was then modified to allow more tolerance for postoperative nerve edema. A third patient showed asymptomatic vocal-cord paresis on immediate postoperative laryngoscopy. Vagus nerve stimulation produces transient vocal-cord dysfunction while the current is on. Nine patients were randomly assigned to receive either high- or low-current stimulation, and seizure frequency was recorded. The high-current stimulation group showed a median reduction in seizure frequency of 27.7% compared to the preimplantation baseline, while the low-current stimulation group showed a median increase of 6.3%. This difference approached statistical significance. The entire population then received maximally tolerable stimulation. The high-current stimulation group showed a further 14.3% reduction, while the low-current stimulation group showed a 25.4% reduction compared to the blinded period. The efficacy of vagus nerve stimulation seemed to depend on stimulus parameters, and a cumulative effect was evident. These results are encouraging, and further study of this modality as an adjunct treatment for epilepsy is warranted.

Resistance to chemotherapy in brain tumors is complex and may involve multiple mechanisms. For commonly used drugs, such as nitrosoureas and platinum compounds, major mechanisms may involve increaded DNA repair or removal of the drug-DNA adducts. For water soluble nitrosoureas and also for platinum compounds, other mechanisms, such as alteration in drug transport, may be important. Another major mechanism may involve glutathione and glutathione-S-transferase pathways. For vinca alkaloids and epipodophyllotoxins p-glycoprotein mediated MDR appears to be the major feature in drug resistance. In addition, alteration of tubulin and topoisomerase II have been described in resistance to vinca alkaloids and epipodophyllotoxins respectively. Recently, increased multidrug resistance associated protein gene expression has been found in glioma cells and brain tumor samples; its clinical significance requires further investigation.

This therapy is, rarely, associated with complications, mostly related to infections, seizures or stimulationinduced side effects. We report a case of a 71-year-old man with a 10-year history of PD who underwent bilateral placement of subthalamic nucleus DBS. As a complication, the patient showed subjective postoperative cognitive decline, and subsequent MRI showed peri-lead oedema, which progressed to large cystic cavitation around the leads without indication of infection. The patient received steroid therapy and the cavitations regressed without surgical intervention. BACKGROUND

AIDS-related primary central nervous system lymphoma (AIDS PCNSL) is a rapidly fatal disease. Conventional therapeutic modalities offer little and new approaches are needed. Previous work has shown that zidovudine (AZT) in combination with other agents is active in retroviral lymphomas. Epstein-Barr virus (EBV) is detected in tumor tissue and cerebrospinal fluid of AIDS PCNSL patients. In a preliminary in vitro study we found that an Epstein-Barr virus-positive B cell line underwent apoptosis on coculture with AZT. This effect was accentuated by the addition of ganciclovir (GCV). We treated five patients with AIDS PCNSL with a regimen consisting of parenteral zidovudine (1.6 g twice daily), ganciclovir (5 mg/kg twice daily), and interleukin 2 (2 million units twice daily). Four of five had an excellent response. Two patients are alive and free of disease 22 and 13 months later; another responded on two separate occasions, 5 months apart, and the last patient responded with a 70-80% regression of tumor but could not be maintained on therapy owing to myelosuppression. We conclude that parenteral zidovudine, ganciclovir, and interleukin 2 is an active combination for AIDS-related central nervous system lymphoma.