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Vagus nerve stimulation (VNS) was shown to reduce seizure frequency in refractory epilepsy patients in two pilot studies. Based on these results, a multicenter, prospectively randomized, parallel, double-blind study of patients with refractory partial seizures was initiated. After a 12-week baseline period, identical vagus nerve stimulators were implanted and patients randomized to either a high or low 14-week VNS treatment paradigm. The primary objective was to demonstrate that high VNS (therapeutic parameters) was more effective in reducing partial seizure frequency than was low VNS (less or noneffective parameters). Patients continued receiving antiepileptic drugs (AEDs) with plasma concentrations held constant throughout the study. We report results of the first 67 patients to exit the 14-week acute phase. After 14 weeks of VNS, 31 patients receiving high VNS experienced a mean seizure frequency percentage reduction of 30.9%, which was statistically significant as compared with the mean seizure frequency percentage reduction of 11.3% in 36 patients receiving low VNS (p = 0.029, t test; p = 0.036, Wilcoxon rank-sum test). In addition to the significant intragroup p-values, mean seizure frequency percentage change reached statistical significance for high VNS (p < 0.001) but not low VNS (p = 0.072) as compared with baseline. Twelve of 31 (38.7%) patients receiving high VNS achieved at least 50% reduction in seizure frequency whereas 7 of 36 (19.4%) patients receiving low VNS experienced at least 50% reduction after 14 weeks. The implant procedure and VNS therapy were well tolerated. Our study confirmed the effectiveness of VNS as treatment for epilepsy patients with refractory partial seizures.

Vagus nerve stimulation (VNS) has demonstrated a significant anticonvulsant effect in preclinical studies, in pilot studies in humans, and in the acute phase of a multicenter, double-blinded, randomized study. After completion of a 14-week, blinded, randomized study, with 31 receiving high (therapeutic) VNS and 36 receiving low (less or noneffective) VNS, 67 patients elected to continue in an open extension phase. During the extension phase, all 67 patients received high VNS. Seizure frequency during the 3-month treatment blocks was compared with a 12-week baseline. For both groups, all periods of high VNS demonstrated a significant decrease in seizure frequency (p < 0.01 level) as compared with baseline. For the 16-18-month period of VNS, data were available for 26 of the 31 patients randomized to high VNS. This group achieved a 52.0% mean seizure frequency percentage reduction as compared with baseline. For those converted from low to high VNS, data were available for 24 of the 36 patients at the 16-18-month time period. This group reported a mean seizure frequency percentage reduction of 38.1% as compared with baseline. No significant change in the safety/side effect profile was reported during long-term follow-up. The previously reported side effects of hoarseness/voice change, coughing, and paresthesia (sensation in neck and jaw) continued to occur during VNS. These side effects were well tolerated. During the follow-up period, 1 patient died of thrombotic thrombocytopenic purpura (TTP) and 5 patients discontinued treatment because of unsatisfactory efficacy.

Stimulation of the vagus nerve for the treatment of refractory seizures of partial onset has been studied in two pilot studies and one randomized, blinded, parallel study. Results from the controlled study have been promising, but more information is required regarding the long-term safety and efficacy of vagus nerve stimulation. A cohort of the first 37 patients to finish the controlled study was examined on a long-term basis. The response of patients at 1 year and 18 months of stimulation revealed that efficacy does not decrease over time. The system is well-tolerated, and no major adverse events occurred with long-term exposure to the stimulation. Normal device end of service occurred in a majority of the patients, with most choosing to have their generators replaced. This analysis demonstrates that stimulation of the vagus nerve for the treatment of refractory epilepsy manifested by seizures of partial onset continues to be safe and effective over extended periods of time.

Over 100 patients have been treated for partial epilepsy using a NeuroCybernetic Prosthesis System (NCP). The NCP System is comprised of an implantable pulse generator, an implantable bipolar stimulating lead, and an external communication system. The lead delivers electrical impulses from the NCP Generator to the vagus nerve, and includes a connector end that plugs into the generator, a silicone insulated lead body, and the helical electrode array that attaches to the nerve. The surgical implantation technique has a significant impact on lead reliability and performance. The lead electrode has performed well to date. Modifications to further improve reliability have been implemented. Clinical experience, case history examples, and voltage measurements are examined. The lead electrode is an important component of the overall system and plays a significant part in the success of vagus nerve stimulation therapy.

Vagus nerve stimulation for the treatment of epilepsy has been studied in medically refractory patients with partial seizures in a randomized, blinded, parallel study. After a 3-month baseline period, the patients were implanted with the Neurocybernetic Prosthesis (NCP) system consisting of the NCP Generator and the Bipolar Vagal Stimulation Lead. Two stimulation paradigms were used, HIGH, which delivers what is considered to be optimal stimulation parameters and LOW, which is considered to be less or noneffective. The system and vagus nerve stimulation were well tolerated and few adverse events have been attributed to either. One patient experienced a period of direct current to the nerve due to a generator malfunction. This resulted in paralysis of the left vocal cord. Efficacy analysis on the first 37 patients to complete the controlled portion of the study has shown that the patients in the HIGH group experienced a mean reduction in seizure frequency of 33.3% and patients in the LOW group experienced a mean reduction in seizure frequency of 8.4%. The difference between the groups is statistically significant with a P value of 0.025. Analysis of seizure duration and intensity does not show any significant change. Ratings of the patient's overall condition fay the patient, investigator, and companion as a measurement of “quality of life” also show improvement in the HIGH group. The results of this interim study demonstrate that vagus nerve stimulation is a safe and effective method of treating partial epileptic seizures.

Electrical stimulation of the vagus nerve (VNS) is a new method for the treatment of patients with medically intractable epilepsy. Sixteen patients, ten of whom participated in a larger multicenter double-blind trial on the efficacy of VNS in epilepsy, and six who participated in pilot studies, consented to participate in the present study. Ten patients received HIGH stimulation and six patients LOW stimulation for the 3-month trial. Cerebrospinal fluid (CSF) samples (16 ml) were collected both before and after 3 months of VNS. Amino acid and neurotransmitter metabolites were analyzed. Four patients responded to VS with more than a 25% seizure reduction after 3 months. Mean and median concentrations of phosphoethanolamine (PEA) increased in responders and decreased in nonresponders. Free GABA increased in both groups but more so in the nonresponders. After 9 months of VS (6-9 months on HIGH stimulation) 4 of 15 patients had more than 40% seizure reduction. There were significant correlations between seizure reduction and increases in asparagine, phenylalanine, PEA, alanine and tryptophan concentrations. Comparison between patients with HIGH or LOW stimulation showed a significant increase in ethanolamine (EA) in the HIGH group and a decrease in glutamine in the LOW group. All patients regardless of response or stimulation intensity showed significantly increased total and free GABA levels. A decrease in CSF aspartate was marginally significant. Other trends were decreases in glutamate and increases in 5-hydroxyindoleacetic acid. Chronic VNS appears to have an effect on various amino acids pools in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

The recurrent laryngeal nerve (RLN) stimulator has been implanted on a limited basis since 1988 for control of spasmodic dysphonia. A similar vagus nerve stimulator has been implanted in a larger series of patients to control epilepsy. The safety and tolerability of these two stimulators were evaluated. In 113 patients implanted with the vagus nerve stimulator, the complication rate was 0.9%. All patients were monitored for vital signs, electrocardiographic changes, and adverse effects. The absence of changes in vital signs and electrocardiograms during vagal stimulation establishes the safety of this treatment. Since placement of the electrode around the vagus nerve is an easier surgical technique than placement deep to the RLN, it seems reasonable to change the technique to implant the stimulator on the vagus in patients with spasmodic dysphonia.

We treated 14 patients with medically refractory partial seizures by stimulation of the vagus nerve in two single-blind pilot studies. Patients received stimulation through an implantable, programmable Neurocybernetic Prosthesis, consisting of a pulse generator and a lead-electrode assembly. The mean reduction in seizure frequency after 14 to 35 months of vagal stimulation was 46.6%. Of the 14 patients, five (35.7%) had a 50% or greater reduction in seizure frequency. Two patients, one of whom had had 10 to 100 seizures per day before stimulation, have been seizure-free for over 1 year. Adverse events were primarily limited to initial hoarseness and a tingling sensation at the electrode site in the neck when the device was activated. Most patients tolerated the device and stimulation well. There were no permanent adverse events. Some cases of medically refractory partial seizures are improved by vagal stimulation.

Background: Chronic vagus nerve stimulation (VNS) continues to be evaluated as an adjunctive treatment for medically intractable seizures. A previous randomized controlled trial of 114 patients demonstrated a significant decrease in seizure frequency during 3 months of VNS at effective stimulation levels. Objective: To evaluate the efficacy of 1 year of VNS therapy for the treatment of medically refractory partial seizures and the relationship between initial and longterm response. Patients and Methods: All patients exiting the randomized controlled study of VNS for treatment of medically refractory partial seizures were offered indefinite treatment extension as part of an open-label trial. One hundred (88%) of 114 patients completed 12 months of VNS treatment at effective stimulation levels. Fourteen patients discontinued VNS treatment prior to 1 year, principally because of the treatment's lack of efficacy. These 14 patients were retained in the present analysis using an intent-to-treat approach. Antiepileptic drug use was monitored throughout the trial. Seizure frequency was analyzed in 4 sequential 3-month treatment periods. Results: Compared with pretreatment baseline, there was a significant decrease in seizure frequency during each of the 3-month treatment periods. Seizure frequency was reduced by a median of 20% during the first 3 months of VNS treatment and by 32% during stimulation months 10 through 12. Response during the first 3 months of VNS treatment was a statistically significant predictor of response at months 10 through 12. The observed reduction in seizure frequency was not explained by overall changes in antiepileptic drug use. Conclusions: The results indicate that VNS remains an effective adjunctive therapy for medically refractory partial seizures over a period of at least 1 year. Response during the first 3 months of treatment is predictive of longterm response.

Fluoxetine, a selective serotonin-uptake inhibitor, has been shown to be effective in the treatment of depression. A series of studies found fluoxetine to be more effective than placebo and to be associated with equivalent efficacy to standard reference tricyclic antidepressants (Stark & Hardison, 1985; Feighner & Cohn, 1985).The selection of a dosage regime for fluoxetine in these studies was based on the information gathered from open dose-ranging investigations. In these studies, treatment starts with one dose level, which is then increased as indicated in the protocol or until increased doses are not tolerated due to side-effects. One of the weaknesses in this method of choosing the likely standard dose of a new antidepressant lies in the inherent bias towards the selection of the higher dose levels. This is particularly true for drugs which are well tolerated.

This was a 6-week, double-blind comparison of fluoxetine, imipramine, and placebo in 89 patients with bipolar depression. Using the criteria of greater than or equal to 50% improvement in the HAMD-total score after at least 3 weeks on study drug, endpoint analysis showed 86% of the fluoxetine-treated patients improved compared with 57% of the imipramine-treated and 38% of the placebo-treated patients. Significantly fewer fluoxetine-treated patients discontinued due to adverse events than did imipramine-treated patients (7% vs. 30%, respectively).

The effects of high-dose fluoxetine (median 80 mg/day), standard-dose imipramine (median 200 mg/day), and placebo were studied in 706 outpatients meeting DSM-III criteria for major depressive disorder. Baseline psychomotor activity of each patient was prospectively categorized as agitated, retarded, or neither. Rates of occurrence of total and significant (leading to discontinuation) activating adverse events (insomnia, agitation, anxiety, nervousness) and sedating events (somnolence, asthenia) were compared between treatments on an overall basis and within categories of baseline psychomotor activity. Additionally, these rates were compared across baseline psychomotor activity for each treatment. Efficacy was evaluated on an overall basis and with respect to baseline psychomotor activity. There was more total activation with fluoxetine than placebo (p = 0.008), but total activation with fluoxetine (28%) showed only a trend (p = 0.092) for being greater than with imipramine (21%). Discontinuations for activation with fluoxetine (5%) did not differ from imipramine (5%). Sedation and discontinuations for sedation with both fluoxetine and imipramine significantly exceeded placebo. The only drug-drug difference in discontinuations was for sedation where imipramine (11%) exceeded fluoxetine (5%; p = 0.008). Only for the occurrence of sedation with imipramine (47% among patients retarded at baseline) was there a significant association with baseline psychomotor activity (p = 0.021). Both fluoxetine and imipramine were superior to placebo and equal in efficacy in decreasing total Hamilton Rating Scale for Depression (HAM-D), the sleep disturbance HAM-D factor, and the anxiety/somatization HAM-D factor scores. These improvements were independent of baseline psychomotor activity.