Effect of high-frequency repetitive transcranial magnetic stimulation on brain excitability in severely brain-injured patients in minimally conscious or vegetative state

Background Repetitive transcranial magnetic stimulation (rTMS) induces prolonged functional changes in the cerebral cortex in normal conditions and in altered states of consciousness. Its therapeutic effects have been variously documented. Objective The aim of this study was to investigate the reactivity of electroencephalography (EEG) and the clinical response in six severely brain-injured patients in an altered state of consciousness (minimally conscious state [MCS] or vegetative state [VS]). EEG rhythm and brain excitability were measured before and after a protocol of high-frequency rTMS. Methods All six patients underwent clinical and neurophysiological evaluation before rTMS and immediately thereafter. EEG data in resting state were acquired at the beginning of the exam (T₀), after rTMS (T₁), and 38 min after rTMS (T₂). From these data the power values were computed using Fast Fourier Transform. Results rTMS over the motor cortex induced long-lasting behavioral and neurophysiological modifications in only one patient in MCS. No significant clinical or EEG modifications were detected in any of the other patients, except for changes in motor threshold and motor evoked potential amplitude over the stimulated motor areas. Conclusions The main finding of the study is the correlation between EEG reactivity and clinical response after rTMS. Reappearance of fast activity and an increase in slow activity were noted in the one patient with transitory arousal, whereas no significant reliable changes were observed in the other patients showing no clinical reactivity.