Feasibility of vagus nerve stimulation-synchronized blood oxygenation level-dependent functional MRI

RATIONALE AND OBJECTIVES. Left cervical vagus nerve stimulation (VNS) by use of an implanted neurocybernetic prosthesis (NCP) system is effective in treating epilepsy, with open data suggesting effectiveness in depression, yet the mechanisms of action are unknown. Our objective was to develop a methodology for performing VNS-synchronized functional magnetic resonance imaging (VNS-fMRI) and then to demonstrate its feasibility for studying VNS effects. METHODS. In nine patients implanted for treatment of intractable depression, a Macintosh computer was used to detect the signal from the implanted VNS stimulator and then to synchronize fMRI image acquisition with its regular firing. RESULTS. With our VNS-fMRI methodology, the blood oxygenation level-dependent response to VNS was shown in brain regions regulated by the vagus nerve: orbitofrontal and parieto-occipital cortex bilaterally, left temporal cortex, the hypothalamus, and the left amygdala. CONCLUSIONS. Vagus nerve stimulation pulses from an NCP system can be detected externally to determine its firing pattern, thus allowing VNS-fMRI studies of VNS-induced brain activity.