Intervention Effect of Transcranial Alternating Current Stimulation (tACS) on Disorder of Consciousness (DOC)

To Explore the Intervention Effect of High Definition-transcranial Alternating Current Stimulation (HD-tACS) on Consciousness Promotion in Patients With Chronic Consciousness Disorders and the Potential Neural Mechanism

To investigate the effect of high definition-transcranial alternating current stimulation(HD-tACS) on consciousness promotion in patients with chronic consciousness disorders and the underlying neural mechanism by EEG.

Forty patients with chronic consciousness disorder who met the inclusion criteria were recruited with the informed consent of the family. All the participants were randomized to receive "active" or "sham" treatment protocol. Stimulation was performed using a alternating stimulator linked to one anodal electrode and four cathodal electrodes. The anodal electrode was placed over the left dorsolateral prefrontal cortex (DLPFC; F3 in the 10-20 international system of EEG placement), and the four cathodal electrodes (AFz, FCz, F7, and C5 in the 10-20 international system EEG placement) were placed around the anodal electrode to form a current loop. Twenty 2 milliampere (mA) sessions (ramp-up and ramp-down periods of 30 and 30 seconds, respectively) were applied for 20 minutes per session, twice daily over 10 consecutive days, and the stimulus frequency was set as 6 Hertz (Hz). Sham tACS was delivered using the same protocol and current intensity, but the period of active stimulation was only during the ramp-up and ramp-down periods of 30 and 30 seconds. Before and after the tACS treatment, the state of consciousness was assessed according to coma recovery scale-revised(CRS-R), and19-channel EEG data were collected.

Inclusion Criteria:

1. patients diagnosed as chronic disorders of consciousness based on CRS-R assessment by at least two professional neurologists;
2. the age requirement is between 18 and 75;
3. vital signs need to be stable;
4. no neuromuscular blockers and sedatives have been used within 24 hours before the study and the entire protocol;
5. no improvement in the state of consciousness was observed within one week before the start of the study.

Exclusion Criteria:

1. previous or current diagnosis of severe neurocognitive degenerative diseases;
2. metal implantation in the head;
3. previous surgical procedures resulted in skull defect;
4. previous history of epilepsy.