Abstract
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Objectives The aim of this study was to evaluate effects on regional cerebral blood flow of trigeminal nerve stimulation (TNS), an investigational neuromodulation intervention, in treatment-resistant epilepsy and depression patients.
Methods A total of 24 [O15]water-PET scans from 4 depressed adults (mean±SD, age: 46.9±5.8, yrs of education: 17.3±1.5, 2M:2F, all right-handed, severity of the 17-item Hamilton Depression Rating Scale 19.5±4.4) were examined. Half of the scans for each subset were acquired while receiving 60 seconds of TNS at maximally tolerated current intensity, and half were acquired while the same apparatus was in place but current was set to zero. During each scan, the onset of TNS occurred at the time the [O15]water bolus was pushed. PET data were analyzed by standardized volume of interest (sVOI) and statistical parametric mapping (spm) methods.
Results The bilateral temporo-occipital cortex (TOC) (in the vicinity of Brodman’s areas 37 and 39) was the brain region demonstrating the most significant decrease in blood flow during TNS (right TOC p<0.0005 after cluster-size based correction, left TOC p=0.002 after correction; peak voxel on both sides p<0.0005). Less extensive deactivations were also seen in the right superior parietal cortex and right sensorimotor cortex (peak-voxel p<0.0005 for both); spm analyses for both regions were corroborated by sVOI analyses. The most significant activations by both spm and sVOI analyses occurred in the medial frontal cortical area, somewhat greater on the right side, particularly in the right medial frontal gyrus (peak-voxel p<0.0005, cluster-corrected p=0.05) and anterior cingulate bilaterally (peak-voxels p<0.0005).
Conclusions TNS was associated with deactivation in TOC, superior parietal, and sensorimotor cortex, and activation in medial frontal cortical areas. Though effects were bilateral, all of the major changes occurring in regional cerebral blood flow during TNS were more striking in the right hemisphere