SPINAL CORD STIMULATION MODULATES FRONTAL DELTA AND GAMMA IN PATIENTS OF MINIMALLY CONSCIOUSNESS STATE

Spinal cord stimulation (SCS) has been suggested as a therapeutic technique for treating patients with disorder of consciousness (DOC). Although studies have reported its benefits for patients, the underlying pathophysiological mechanisms remain unclear. The aim of this study was to measure the effects of SCS on the EEG of patients in a minimally conscious state (MCS), which would allow us to explore the possible workings underpinning of the approach. Resting state EEG was recorded before and immediately after SCS, using various frequencies (5 Hz, 20 Hz, 50 Hz, 70 Hz and 100 Hz), for 11 patients in MCS. Relative power, coherence, S-estimator and bicoherence were calculated to assess the EEG changes. Five frequency bands (delta, theta, alpha, beta and gamma) and three regions (frontal, central and posterior) were divided in the calculation. The main findings of this study were that: (1) significantly altered relative power and synchronisation was found in delta and gamma bands after one SCS stimulation using 5 Hz, 70 Hz or 100 Hz; (2) bicoherence showed that coupling within delta was significantly decreased after stimulation using 70 Hz, while reduction of coupling between delta and gamma was found when using 5 Hz and 100 Hz. However, SCS of 20 Hz, 50 Hz and sham stimulation did not induce changes in any frequency band at any region. This study showed EEG evidence that SCS can modulate the brain function of MCS patients, speculatively by activating the formation-thalamus-cortex network. (C) 2017 IBRO. Published by Elsevier Ltd. All rights reserved.