GLOBAL SYNCHRONIZATION INDEX AS A NEW INDICATOR FOR TRACKING COGNITIVE FUNCTION CHANGES BY TRANSCRANIAL DIRECT CURRENT STIMULATION IN A TRAUMATIC BRAIN INJURED PATIENT: A CASE REPORT

Abstract

Traumatic brain injury (TBI) is a leading cause of long-term neurological disability such as cognitive impairments and executive dysfunction. Noninvasive transcranial direct current stimulation (tDCS), which can change brain excitability, was introduced and has been applied for therapeutic purposes regarding cognitive dysfunction after TBI. We investigated the effect of tDCS on the cognitive function and cortical power distribution by dual analysis of resting state Electroencephalography (EEG) with Global Synchronization Index (GSI) and Low-Resolution Brain Electromagnetic Tomography Analysis (LORETA) in a TBI patient. A 77-year-old male, who went through a traumatic brain injury showed severe impairment of cognitive function. We performed 20 sessions of 2mA tDCS over the left dorsolateral prefrontal cortex (DLPFC) and measured Korean version of the Mini-Mental Status Examination (K-MMSE) and Rancho Los Amigos (RLA) level at baseline, 10 days and 20 days each after tDCS. EEG was also performed on same days with K-MMSE and RLA tests. After tDCS, the cognitive function measured by K-MMSE and RLA level were improved. GSI showed decrease in the low frequency band (theta wave) and increase in high frequency bands (alpha and beta wave) (Table 1). LORETA analysis showed incresed cortical activation components in high frequency bands at 20 days after tDCS (Figure 1). Graphical representation of the LORETA results comparing the EEG between baseline and tDCS 10 (a) and between baseline and tDCS 20 (b). Blue-light blue colors indicate increased component and yellow-red colors indicate decreased component of each EEG bands. We suggest that tDCS might be effective in TBI patients, and the alterations of cognitive networks could be effectively studied using GSI analysis together with LORETA.