A 1-Year Pilot Study of Vagus Nerve Stimulation in Treatment-Resistant Rapid-Cycling Bipolar Disorder

Objective: Vagus nerve stimulation (VNS) appears to be an effective treatment option for patients with treatment-resistant unipolar and bipolar depression. The aim of the present study was to investigate the efficacy of VNS in a group of patients with treatment-resistant rapid-cycling bipolar disorder (RCBD) who were excluded from previous trials.

Method: Nine outpatients with a DSM-IV-TR diagnosis of treatment-resistant RCBD were treated for 40 weeks with open-label VNS. The first patient was enrolled in June 2001, and the last patient completed the study in July 2005. Patients recorded their depression and mania mood symptoms on a daily basis throughout the study using the National Institute of Mental Health prospective life charting methodology and daily mood ratings. Patients were assessed every 2 weeks during the 2-month baseline period before device activation, every 2 weeks for the remaining 40 weeks of the study, and at the end of the study with the 24-item Hamilton Rating Scale for Depression (HAM-D-24), the 10-item Montgomery-Asberg Depression Rating Scale (MADRS), the Young Mania Rating Scale (YMRS), the Clinical Global Impressions (CGI) scale, the Global Assessment of Functioning (GAF) scale, and the 30-item Inventory of Depressive Symptomatology Self-Report (IDS-SR-30). Any adverse events or device complications were also recorded at each visit. The prospective life charts were analyzed by calculating the area under the curve. Statistical analysis was performed with a mixed-model repeated-measures regression analysis for repeated measures of the various rating scales. Significant p values were <= .05.

Results: Over the 12-month study period, VNS was associated with a 38.1% mean improvement in overall illness as compared to baseline (p = .012), as well as significant reductions in symptoms as measured by the HAM-D-24 (p = .043), MADRS (p = .003), CGI (p = .013), and GAF (p < .001) rating scales. Common adverse events were voice alteration during stimulation and hoarseness.

Conclusion: These data suggest that VNS may be an efficacious and well-tolerated treatment option for patients with treatment-resistant RCBD. Currently, no comparison is available in the literature. Larger randomized trials are needed to verify these findings.