132 The Underlying Effect of Burst Stimulation on Chronic Pain Using Multimodal Neuroimaging - EEG, fMRI and PET

Abstract

Abstract INTRODUCTION Minimally invasive neuromodulation such as spinal cord stimulation (SCS) and occipital nerve stimulation (ONS) have shown to be successful for treatment of different types of pain such as chronic back or leg pain, complex regional pain syndrome (CRPS), and fibromyalgia. Recently, novel stimulation paradigm called burst stimulation was developed that suppresses pain to better extent than classical tonic stimulation. From clinical point of view, burst stimulation is very promising; however, little is known about its underlying mechanism. Hence, in this work we investigate mechanism of action for burst stimulation in different patient groups and controls using different neuroimaging multimodalities such as EEG, fMRI and PET. METHODS Control subjects and patients with chronic back or leg pain, CRPS, or fibromyalgia enrolled for study. Both controls and patients received SCS or ONS and sham, tonic, and burst stimulation in fMRI, PET, and EEG. RESULTS >EEG shows significant changes for burst stimulation compared to tonic and sham stimulation; evident by increased activity at dorsal anterior cingulate cortex (dACC), dorsolateral prefrontal cortex (dPFC), primary somatosensory cortex, and posterior cingulate cortex (PSC) in alpha frequency band. PET further confirmed by showing increased tracer capitation for burst in dACC, pregenual anterior cingulate cortex (pgACC), parahippocampus, and fusiform gyrus. Furthermore, fMRI showed burst changes in dACC, dPFC, pgACC, cerebellum, hypothalamus, and premotor cortex. A conjunction analysis between tonic and burst stimulation demonstrated theta activity is commonly modulated in somatosensory cortex and PSC. CONCLUSION Our data suggest that burst and tonic stimulation modulate ascending lateral and descending pain inhibitory pathways. Burst stimulation adds by modulating the medial pain pathway, possibly by direct modulation of spinothalamic pathway, as suggested by animal research. Burst normalizes an imbalance between ascending pain via medial system and descending pain inhibitory activity, which could be a plausible reason it's better than to tonic stimulation.