EEG Microstates During Multisensory Stimulation: Assessing the Severity of Disorders of Consciousness and Distinguishing the Minimally Conscious State

<b>Background:</b> The clinical assessment of Disorders of Consciousness (DOC) has long been constrained by the subjectivity of behavioral scales and the low-temporal resolution of neuroimaging techniques. There is an urgent need for objective, high-temporal-resolution biomarkers to improve the accuracy of DOC severity evaluation and sub-state differentiation. This study aims to develop a resting-state/task-state dual-modality EEG microstate analysis method. By integrating a multisensory stimulation paradigm with a resting-state global template, we seek to verify the validity and clinical utility of this method in quantitatively assessing the severity of DOC sub-states, namely Minimally Conscious State-positive (MCS+), Minimally Conscious State-negative (MCS-), and Vegetative State (VS). <b>Methods:</b> A total of 27 subjects were enrolled, including 9 healthy controls (HC), 6 MCS+ patients, 6 MCS- patients, and 6 VS patients. A multisensory stimulation paradigm (visual, olfactory, and combined visual-olfactory) was applied, and EEG microstates were extracted using a revised K-means clustering algorithm. Key microstate parameters (duration, global field power, and coverage) were quantified for systematic analysis. <b>Results:</b> During the resting state, the HC group exhibited a significantly posterior parietal-dominant distribution of Microstate D, while this parameter showed a gradient attenuation pattern corresponding to the severity of consciousness impairment in the DOC group (<i>p</i> < 0.05). During the task state, the HC group showed a significant multisensory effect under combined visual-olfactory stimulation; within the DOC group, MCS+ patients demonstrated stronger task-related responses compared to MCS- and VS patients. <b>Conclusions:</b> The gradient attenuation of resting-state Microstate D parameters reflects the severity of DOC, and task-specific responses to multisensory stimulation serve as a potential biomarker for distinguishing MCS+ patients. This dual-modality EEG microstate analysis method provides an objective, high-temporal-resolution basis for the precise clinical evaluation of neurological function in DOC patients.