Neurorecovery and Cerebral Hemodynamics in Patients Undergoing Transcranial Direct Current Stimulation with Disorders of Consciousness (DoC): A Systematic Review

Masood  Zangi; Mohammadreza  Hajiesmaeili; Majid  Mokhtari; Reza  Goharani; Neda  Tajaldin; Mahdi  Amirdosara

doi:10.18502/aacc.v11i5.19937

Masood Zangi Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Mohammadreza Hajiesmaeili Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Majid Mokhtari Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Reza Goharani Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Neda Tajaldin Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Mahdi Amirdosara Critical Care Quality Improvement Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

DOI: https://doi.org/10.18502/aacc.v11i5.19937

Keywords: Disorders of consciousness; Non-invasive brain stimulation; Transcranial direct current stimulation; Cerebral hemodynamics

Abstract

Background: Disorders of consciousness (DoC), encompassing coma, vegetative state/unresponsive wakefulness syndrome (VS/UWS), and minimally conscious state (MCS), result from severe brain injuries that disrupt neural networks responsible for arousal and awareness. Non-invasive brain stimulation (NIBS) techniques, including transcranial direct current stimulation (tDCS) and its variants, such as high-definition tDCS (HD-tDCS) and transcranial alternating current stimulation (tACS), offer promising therapeutic strategies. This review synthesizes evidence on the efficacy of NIBS, focusing on its impact on brain hemodynamics, neurophysiology, and clinical outcomes.

Methods: To this end, we searched the international databases (Web of Science, PubMed, Scopus) and extracted studies using the appropriate keywords. The Newcastle-Ottawa Scale (NOS) was used to assess the methodology and quality of the studies.

Results: Research demonstrates that tDCS and its advanced forms improve EEG patterns, including alpha and theta band power, reduce P300 latency, and enhance cortical-cortical and thalamocortical connectivity, correlating with better behavioral outcomes, as measured by the Coma Recovery Scale-Revised (CRS-R). Moreover, personalized protocols based on MRI simulations and multimodal therapies, such as combining NIBS with music stimulation or robotic rehabilitation, further optimize outcomes by targeting specific brain areas and enhancing network reconfiguration. The dual application of HD-tDCS with transcutaneous auricular vagus nerve stimulation (taVNS) has also shown synergistic effects on EEG microstate dynamics and CRS-R scores in MCS patients.

Conclusion: Overall, NIBS presents a promising approach for enhancing consciousness recovery, though challenges in protocol optimization and understanding the mechanisms of action remain. Future research should continue to explore these techniques' full potential, particularly through personalized, multi-target stimulation strategies.