Pretreatment cerebral metabolic activity correlates with antidepressant efficacy of vagus nerve stimulation in treatment-resistant major depression: A potential marker for response?

Background: Pretreatment brain activity in major depressive disorder correlates with response to antidepressant therapies, including pharmacotherapies and transcranial magnetic stimulation. The purpose of this trial was to examine whether pretreatment regional metabolic activity in selected regions of interest (ROIs) predicts antidepressant response following 12 months of vagus nerve stimulation (VNS) in 15 patients with treatment-resistant major depression (TRMD). Methods: Fluorodeoxyglucose positron emission tomography (FOG PEI') was used to assess regional mean relative cerebral metabolic rate for glucose (CMRGIu) in four ROIs (anterior insular, orbitofrontal, anterior cingulate, and dorsolateral prefrontal cortices) at baseline (prior to VNS activation). Depression severity was assessed at baseline and after 12 months of VNS using the Hamilton Depression Rating Scale (HDRS), with response defined as >= 50% reduction in HDRS from baseline. Results: Baseline CMRGIu in the anterior insular cortex differentiated VNS responders (n = 11) from nonresponders (n = 4) and correlated with HDRS change (r =.64, p =01). In a regression analysis, lower anterior insular cortex CMRGIu (p =.004) and higher orbitofrontal cortex CMRGIu (p =.047) together predicted HDRS change (R-2=.58, p =.005). In a whole brain, voxel-wise analysis, baseline CMRGIu in the right anterior insular cortex correlated with HDRS change (r =.78, p =001). Limitations: Sample size was small, limiting statistical power; patients remained on their psychiatric medications; study was open-label and uncontrolled. Conclusions: This preliminary study suggests that pretreatment regional CMRGIu may be useful in predicting response to VNS in TRMD patients. (C) 2012 Elsevier B.V. All rights reserved.