Combined Behavioral and Mismatch Negativity Evidence for the Effects of Long-Lasting High-Definition tDCS in Disorders of Consciousness: A Pilot Study.

Xiaoyu Wang,Zhongqi Gao,Jianghong He,Jinju Li,Yongkun Guo,Hui Zhang,Tianlin Zhou,Yunge Zhang,Fengyu Cong,Yingxin Li

doi:10.3389/fnins.2020.00381

Abstract

ObjectiveTo evaluate the effects of long-term High-definition transcranial direct current stimulation (HD-tDCS) over precuneus on the level of consciousness (LOC) and the relationship between Mismatch negativity (MMN) and the LOC over the therapy period in patients with Disorders of consciousness (DOCs).MethodsWe employed a with-in group repeated measures design with an anode HD-tDCS protocol (2 mA, 20 min, the precuneus) on 11 (2 vegetative state and nine minimally conscious state) patients with DOCs. MMN and Coma Recovery Scale-Revised (CRS-R) scores were measured at four time points: before the treatment of HD-tDCS (T0), after a single session of HD-tDCS (T1), after the treatment of 7 days (T2) and 14 days (T3). A frequency-deviant oddball paradigm with two deviation magnitudes (standard stimulus: 1000 Hz, small deviant stimuli: 1050 Hz, large deviant stimuli: 1200 Hz) was adopted to elicit MMN.ResultsSignificant improvements of CRS-R score were found after 7-day (T2) and 14-day (T3) treatment compared with baseline (T0). Regarding the MMN, significant improvements of MMN amplitudes were observed after a single session of stimulation (T1), 7-day (T2) and 14-day treatment (T3) compared with baseline (T0). Additionally, there were significant negative correlations between CRS-R scores and MMN amplitudes elicited by both large and small deviant stimuli.ConclusionLong-term HD-tDCS over precuneus might improve signs of consciousness in patients with DOCs as measured by CRS-R total scores, and MMN could be an assistant assessment in the course of tDCS treatment.

Highlights

Disorder of consciousness (DOCs) are clinical states where consciousness and reactivity to external stimuli have impaired by severe brain injury
After 14-day HD-transcranial direct current stimulation (tDCS) stimulations, 11/11 patients showed an increase in the Coma Recovery Scale-Revised (CRS-R) total scores (Table 2)
Post hoc revealed that, compared with the baseline (T0 with mean = 8.909), statistically significant improvements were observed after 7-day (T2 with mean = 10.455, p = 0.016, Cohen’s d = 1.324) and 14-day treatment (T3 with mean = 11.237, p = 0.004, Cohen’s d = 2.067), whereas there was no statistically significant improvement after single session of stimulation (T1 with mean = 9.091, p > 0.05, Cohen’s d = 0.156)

Summary

Introduction

Disorder of consciousness (DOCs) are clinical states where consciousness and reactivity to external stimuli have impaired by severe brain injury (such as traumatic brain injury, stroke, Hemorrhage, and so forth). Based on the behavioral observations, patients who suffered from DOCs could be categorized as vegetative state/unresponsive wakefulness syndrome (VS/UWS) and minimally conscious state (MCS) group (Giacino et al, 2004). Current evidence suggests that non-invasive brain stimulation (NIBS) including transcranial direct current stimulation (tDCS), Transcranial magnetic stimulation (TMS), and low-level laser therapy (LLLT), seems to be promising treatments (Thibaut et al, 2014; Xia et al, 2017; Poiani et al, 2018; Huang et al, 2019). Xia et al (2017) reported that Hz multisession repetitive TMS applied to the left dorsolateral prefrontal cortex (DLPFC) has a potential benefit for the rehabilitation of patients with severe DOC, with an increase in CRS-R total scores in 5 out 5 MCS patients and 4 out of VS/UWS patients after 30-day treatment. TDCS has received considerable attention in the field of neuroscience because of its low cost, portability, safety, tolerance (Bikson et al, 2016) and combination with robotic-based rehabilitation (Calabro et al, 2016)

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Conclusion