Magnetoencephalography to Image the Acute Modulation of Brain Activity by Spinal Cord Stimulation Treatment in Chronic Pain Patients

Abstract

Background: Spinal cord stimulation (SCS) is a last resort therapy for chronic pain syndromes, of which the exact mechanisms of action remain unknown. Although often effective, not all patients have sufficient pain reduction after implantation. Objective: Analyse the acute effects of tonic and burst SCS on spectral features in the whole brain and in specific brain regions using magnetoencephalography (MEG). Methods: Resting state MEG recordings of seventeen patients with SCS set to a cyclic stimulation program were analysed. Spectral analysis was done by computing power spectrum densities and calculating the ratio between different frequency bands. Time frequency decompositions were then computed to image the spectral changes over time. Results: I showed a shift of power to the 7-10 Hz range during tonic and burst stimulation ON, and that burst stimulation modulated the regions involved in the medial pathway more than tonic stimulation did. I also hypothesised that burst stimulation has a lingering effect on the neuronal activity after it is switched OFF. Lastly, I showed that alpha power decreased at the moment the stimulation switched ON or OFF. Conclusion: Although most findings were not statistically significant, the results were similar to the results of studies with patients who had longer exposure to SCS. There is still room for improvement in SCS treatment, and MEG analysis of acute modulation can help to gain more insight in its working mechanisms.