Evaluating the Effect of Repetitive Transcranial Magnetic Stimulation on Disorders of Consciousness by Using TMS-EEG

Abstract

Background: The modulation efficacy of Transcranial magnetic stimulation (TMS) on consciousness improvement of patient with disorder of consciousness (DOC) has not been definitely confirmed. Objective: This study proposes TMS-EEG to assess effects of repetitive TMS (rTMS) on brain modulation of DOC. Methods: Twenty sessions of 10 Hz rTMS were applied over the dorsolateral prefrontal cortex for a patient with DOC. Measures of Coma Recovery Scale-Revised (CRS-R) score, TMS-evoked potential (TEP), perturbation complexity index (PCI), and global mean field power (GMFP) were used to evaluate the consciousness level of the patient at three intervals: before the rTMS protocol (T0), immediately after one session rTMS (T1), and immediately after 20 sessions (T2). Results: It was found that the patient was diagnosed of a minimally conscious state minus (MCS-) by means of CRS-R at the interval of T0, however the TEP and PCI indicated the patient was vegetative state (VS). At the interval of T1, there was not any clinical behavioral improvement in CRS-R, but we could find significant changes in TEP, PCI, and GMFP. At the interval of T2 there was a significant increase of consciousness level according by CRS-R score, PCI value, TEP, and GMFP after 20 sessions of 10 Hz rTMS on the patient with DOC. Conclusions: We demonstrated that TMS-EEG might be an efficient assessment tool for evaluating rTMS protocol therapeutic efficiency in DOC.

Keywords: EEG; TMS-EEG; disorder of consciousness; perturbation complexity index; rTMS.

Figure 1

TMS protocol for the patient. (A) Time points of the protocol, TMS were delivered at left-DLPFC lasting for 20 consecutive days. CRS-R score was assessed each day from the baseline to day 30. (B) Single pulse TMS evoked EEG recording before the protocol were used as baseline (T0) and that immediately after one session were used as the one session assessment (T1). From day 2 to day 19, there were no TMS and EEG evaluation. Single pulse TMS evoked EEG recorded immediately after the 20 sessions were used as assessment of the whole protocol (T2).

Figure 2

TMS evoked potential and butterfly plots at three time points: T0, T1, and T2. (A) TMS evoked potentials of mean of healthy subjects and patient at three time points. Shadow area means 10 ms before to 20 ms after the TMS onset. (B–D) Butterfly plots of patient at three time points. Source modeling corresponding to each TEP peaks is given under the butterfly plots. Last row of each figure gives the significant activation distribution. White cross shows the stimulation site.

Figure 3

GMFP calculated of patient at three time points and the mean of healthy subjects. Red lines show the GMFP curves of the patient at T0 (A), T1 (B), and T2 (C). Black lines show the mean GMFP curves of healthy subjects. The gray and red shadow means standard deviation of patient and healthy subjects, respectively. Black area with white line show 10 ms before and 20 ms after TMS onset.