Central Effects of Occipital Nerve Electrical Stimulation Studied by Functional Magnetic Resonance Imaging

Objective: To study the central effects of occipital nerve stimulation (ONS) using functional magnetic resonance imaging (fMRI). Materials and Methods: After phantom measurements, blocked design fMRI scanning was performed during intermittent ONS in a healthy volunteer with implanted electrodes connected to an external generator. To assess the effect of frequency and stimulation mode, seven different frequencies in either tonic or burst mode were generated by a neurostimulator. Results: A qualitative analysis of the main effect of ONS demonstrated significantly decreased activity within the bilateral primary visual, auditory, and somatosensory cortices and in the amygdala. Significant increased activity was observed bilaterally in the thalamus, frontal, and parietal areas and the cerebellum. Subsequently, quantitative analysis revealed that, unlike tonic mode stimulation, burst mode stimulation appeared to be frequency-dependent. Conclusions: This study demonstrates the feasibility and safety of fMRI studies with simultaneous ONS in a subject with externalized electrodes. The activation and deactivation pattern induced by ONS depends on stimulation mode and frequency.