Transcranial Alternating Current Stimulation in Patients With Disorders of Consciousness

Clinical Study on Efficacy and Mechanism of HD-tACS in Patients With Prolonged Disorders of Consciousness

In recent years, many literatures have reported that tACS, as a non-invasive electrical brain stimulation technique, has been applied in depression, schizophrenia, dementia and other fields.

The goal of this study is to explore the clinical efficacy and mechanism of action of HD-tACS in patients with chronic disorders of consciousness.The main questions it aims to answer are:

1. Explore the neurophysiological effects of HD-tACS on patients with chronic disorders of consciousness under theta and gamma frequency stimulation, and observe its impact on behavioral changes and long-term prognosis;
2. Further investigate the awakening mechanism of consciousness disorders through HD-tACS stimulation using multimodal assessment;
3. Clarify the role of theta and gamma neural oscillations in consciousness disorders, providing new targets for the pathogenesis and treatment of Disorders of Consciousness .

Background: tACS is a transcranial nerve regulation technique ,it has been applied in depression, schizophrenia, dementia and other fields. However, the exact mechanism of tACS has not been fully elucidated, and there are few reports about the effect of tACS stimulation on patients with consciousness disorder at home and abroad.

Objective: The study aimed to investigate the reactivity of electroencephalography (EEG) and the clinical response of patients with disorders of consciousness and explore the neuromodulatory effects of HD-tACS in patients with chronic disorders of consciousness.

Method: Based on inclusion and exclusion criteria, patients with disorders of consciousness are categorized into chronic coma, vegetative state (VS), and minimally conscious state (MCS) groups. General and clinical data of the patients are collected. Assessments using the CRS-R scale and resting-state EEG are conducted before and after the trial. The trial is designed as a randomized controlled experiment, divided into an HD-tACS real stimulation group and a sham stimulation group. In the real stimulation group, different frequencies (40Hz gamma, 4Hz theta) of stimulation are applied to the left dorsolateral prefrontal cortex, with a current intensity of 2mA for 20 minutes per day, continuously for 5 days. In the sham stimulation group, the tACS stimulation mode and frequency are consistent with the real stimulation group, but current is only passed during the first and last 30 seconds of the entire 20-minute stimulation period. EEG is collected for all patients before stimulation, on the first day of stimulation, and after the stimulation ends. Follow-ups include CRS-R scale and GOS-E scores after 3 months and GOS-E scores after 6 months.

Inclusion Criteria:

• 1. Patients with consciousness disorders for more than 28 days following severe brain injury, assessed by the CRS-R scale to meet the criteria for VS or MCS; 2. Aged between 14 and 80 years; 3. Stable vital signs; 4. No neuromuscular function blockers and no sedation within the prior 24 hours;

Exclusion Criteria:

• 1. Locked-in syndrome; 2. Contraindications for EEG examination;HD-tACS stimulation. 3. Contraindications for MRI scanning, such as the presence of internal metallic implants; 4. Diseases and factors that may affect brain function assessment, such as metabolic disorders, poisoning, shock, etc.