ИСТИНА

ABSTRACT. Development of approaches to objective assessment of consciousness experience in patients with chronic disorders of consciousness (DOC; i.e., vegetative state [VS] and minimally consciousness state [MCS]) is one of the most important direction in this study area. TMS-EEG-derived perturbation complexity index (PCI), which expresses in a numerical form the response of cortical neurons to the magnetic stimulation, allows differentiating unconscious states and states with preserved consciousness. Here, we applied the TMS-EEG technique with PCI calculation in chronic DOC patients. Data were obtained for 38 cases (20 VS patients, median CRS-R score 6 [5;6]; 18 MCS, median CRS-R score 13 [11;18]). In 66% MCS patients PCI value was within the range of 0.31-0.50, i.e., above the PCI* threshold value = 0.31 for absence or presence of consciousness; in 6 patients PCI values ranged from 0.17 to 0.30, which may be due to the variability of TMS-EEG responses in patients with severe structural brain lesions. In 90% VS patients PCI values ranged from 0.1 to 0.29, i.e., below PCI*=0.31. In addition, 2 VS patients demonstrated complex differentiated responses while having no clinical signs of conscious activity. PCI values correlated with the results of clinical assessment (CRS-R total score; Spearman r = 0.59, p=0.0002). Despite the sophisticated process of data collection and processing, TMS-EEG with PCI calculation may be viewed as a reliable method of an objective assessment of the presence or absence of consciousness in DOC patients. Of particular interest are VS patients with complex response that may potentially indicate some preserved consciousness activity which is not accessible during clinical evaluation.