Summary: Purpose:To determine the effect of changes in device settings and duty cycle (on and off times) on the efficacy of vagus nerve stimulation (VNS) for refractory epilepsy. In the long-term XE5 study of VNS for intractable epilepsy, the median reduction in seizure frequency improved significantly after 1 year of follow-up. A central question is whether device changes improve efficacy. We analyzed the effects of device parameter changes on seizure frequency in 154 subjects who completed the study and who had complete data for analysis.Methods: Retrospective analysis of device changes during the XE5 long-term study of VNS. During the XE5 long-term follow-up study, the subject's device settings were modified within a Food and Drug Administration (FDA)-approved range of output current, pulse duration, frequency, on time, and off time. Significant changes in device settings occurred after 3 months. We investigated the relationship between percentage reduction in seizures and changes in device parameters between the 3-and 12-month visits. Within-group comparisons were performed for those who continued on standard on/off cycle of 30 s on and 5 min off, and those with the most common off times of 3, 1.8, and <1.1 min.Results: Output current, pulse duration, frequency, and off time changed significantly between the 3-and 12-month longterm follow-ups. For the group as a whole, changes in device settings were not correlated with an improvement in efficacy. However, a significant improvement in efficacy occurred in a subgroup whose off time was reduced to Յ1.1 min. In this group, the median reduction in seizures improved from 21% before the change in off time, to 39% after the change in off time (Wilcoxon Signed-Rank, p ס 0.011). The responder rate (>50% reduction in seizures) also significantly improved from 19 to 35% (McNemar's test, p ס 0.046). Conclusions:The data from this retrospective analysis indicate that device changes were not the primary determinant of increased efficacy at 12 months of long-term follow-up. In general, patients who remained on the original settings of 30 s on and 5 min off continued to respond or improve in their response over the 1-year period. However, some patients may benefit from reductions in off time (increases in duty cycle). In a subgroup initially resistant to VNS, a change in off time to Յ1.1 min off did result in significant improvements in efficacy. Key Words: Vagus nerve stimulation-Device changesDuty cycle.Vagus nerve stimulation (VNS) has emerged as an effective adjunctive treatment for medically refractory epilepsy (1-7). In the long-term XE5 study, efficacy improved during 1 year of exposure to VNS, indicating a cumulative effect of VNS on seizure frequency (7). At 1 year, the median reduction in seizures improved from 34 to 45%, and 20% had a >75% reduction in seizures (7). However, the impact of device settings on long-term efficacy is poorly understood. Two pivotal trials, E03 and E05, found that device settings of 30 s on/5 min off are safe and effective (4,5). A ...
Most plan report cards that compare the performance of health plans have framed the decision about plan choice as an opportunity to get better-quality care. This study uses a controlled experimental design to examine the effect of reframing the health plan choice decision to one that emphasizes protecting oneself from possible risk. The findings show that framing the health plan decision using a risk message has a consistent and significant positive impact on how consumers comprehend, value, and weight comparative performance information.
Introduction: Nitrous oxide is a commonly abused inhalant drug. It is known to precipitate vitamin B12 deficiency when used chronically and acutely, especially in people having marginal vitamin B12 reserve.Case report: We are presenting a case of nitrous oxide "whippit" abuse in a thirty-three-year-old male with bizarre behavior and delusions. The patient had low normal levels of vitamin B12 (202 pg/ml), but he had markedly high methylmalonyl CoA (1078 nmol/L) and homocysteine (48.4 mcmol/L). Treatment with intramuscular cobalamin led to a resolution of his psychosis.Discussion: This case report highlights the need to consider vitamin B12 deficiency in patients who arrive at a hospital with psychiatric manifestations and who report having a history of nitrous oxide exposure or abuse in the recent or remote past. A review of the literature on the neuropsychological manifestations of vitamin B12 deficiency is provided.
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