Based on comprehensive clinical-neurological, neuropsychological, immunological, and genetic studies, the dissertation provides a theoretical justification and a new solution to the scientific task of improving the diagnostic and differential diagnostic tactics of patients with major neurocognitive disorders of neurodegenerative (MNCDD)and vascular etiology (MNCVD) and mild neurocognitive disorders of various genesis (MLNCD). The formation of cognitive deficits from MNCDD of various etiology was characterized by the peculiarities of the dynamics of changes in neuropsychological status, namely: at the early stage of MNCDD, spatial and mnestic disorders prevailed, in the case of MNCVD - executive dysfunction. During the further progression of these diseases to a moderate stage, these differences are more blurred and difficult to distinguish. In patients with MNCVD, less intellectual and memory disorders were determined compared to MNCDD: according to the MMSE scale, less pronounced disturbances in orientation (p = 0.0053) and memory (p = 0.0058), according to the MoSA scale, less pronounced orientation disorders (p = 0 .0150) and "delayed reproduction" (p = 0.0334), according to the FAB scale in the "phonetic speech speed" subtests (p = 0.0205). According to individual subtests of the ADAS-cog scale, the most significant differences were noted in subtests for word recognition (p = 0.0103), spoken language ability (p = 0.0208). Differences were established depending on the degree of severity of the cognitive deficit. During the study of the neurocognitive profile in patients with MLNCD on the MMSE scale, there were no probable differences in the total number of points (p = 0.6209) for MLNCVD and MLNCDD, however, more pronounced memory disorders, especially delayed reproduction, prevailed in patients with MLNCD of a degenerative genesis (p = 0.0102), orientations (p = 0.0046). Patients with MLNCVD have regulatory cognitive disorders - attention and calculation (р = 0.0443), impaired planning and organization of activities. According to the results of a comparative analysis of the features of the psycho-emotional sphere by separate domains of the NPI scale in patients with MNCVD, depressive disorders were the most common symptom both for mild and moderate severity than for MNCDD (p = 0.0284). Sleep disorders (p = 0.0479), (p = 0.0038), irritability/lability of mood (p = 0.0492), (p = 0.0421) were more often observed in patients with MLNCDD with the same degree of severity. Patients with MLNCDD significantly more often demonstrated anxiety (p = 0.0040) and irritability (p = 0.0013) compared to the MLNCVD group. In patients with MNCDD with a mild degree of severity, there was a violation of functional activity in everyday life, which was characterized by a loss of the ability to perform complex types of (instrumental) activity with relative preservation of the ability to care for oneself, in patients with MNCVD with a moderate degree of severity, a violation of elementary types of (basic) daily activity (dressing). There were no significant impairments of functional activity in everyday life according to the BADLS scale in patients with MNCD of various etiologies, except for differences in the subtests of the scales: "ability to make purchases" (p = 0.0013), "orientation in time" (p = 0.0111). It was established that the concentrations of IL-17A and IL-23 in the blood serum of patients with MNCD were significantly higher than in the control group (р = 0.0335), (р = 0.0265). The level of IL-17A in the blood serum of patients with MNCDD was significantly higher (p = 0.0481) compared to patients with MNCVD and the control group (p = 0.0023). There were no significant differences in the concentration of pro-inflammatory cytokines IL-17A and IL-23 in the blood serum in patients with MLNCD and in the control group, but significant differences were found for IL-17A - between patients with MLNCDD and the control group (p = 0.0436), for IL-23 – between patients with MLNCDD (p = 0.0019) and control group (p = 0.0019) and subgroups with MLNKDD and MLNCVD (p = 0.0004). Such results can confirm that MLNCD of degenerative genesis can be an early stage of MNCDD, and increased concentrations of IL-17A and IL-23 are an additional marker of the risk of progression of MLNCD in MNCDD. In patients with MNCDD, significant correlations were established between the serum concentration of IL-23 and neurocognitive scales: MMSE (r = -0.553; p = 0.032), MoCA (r = -0.592; p = 0.020), ADAS˗cog (r = 0.760; p = 0.001). The genetic study did not reveal the p.429T/G presenilin 1 (PSEN1) gene polymorphism in the examined patients with MNCD (homozygous OR = 100%), which indicates the absence of this genetic marker in the studied population.
