Structural and functional comparisons in cognitive impairments in patients with multiple sclerosis

Background. Multiple sclerosis (MS) is an inflammatory demyelinating and neurodegenerative disease characterized by a variety of neurological symptoms. Cognitive impairment is an important clinical aspect of MS and require careful interviewing and neuropsychological testing to detect it. Contrast-enhanced magnetic resonance imaging (MRI) is the primary diagnostic method in MS, which helps confirm the presence and assess the extent of structural damage to the brain and spinal cord. The purpose of the study was to determine the frequency and severity of cognitive impairment in patients with relapsing-remitting multiple sclerosis, taking into account the localization of brain lesions according to MRI. Materials and methods. Seventy-two patients with a diagnosis of relapsing-remitting MS according to the McDonald criteria (2017) were examined. All of them underwent a thorough neurolo-gical, neuropsychological, and instrumental examination. The average duration of the disease was 8.2 ± 0.8 years. The average score on the Expanded Disability Status Scale was 3.38 ± 0.18 points. Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test 3 (PASAT-3), and Montreal Cognitive Assessment (MoСA) were used to assess the neuropsychological status of patients. All participants underwent a 1.5T MRI of the brain with dotavist contrast enhancement. Results. A thorough survey of examined patients with MS revealed the presence of complaints of cognitive decline in 91.67 % of cases (66 patients). The average score on the SDMT was 32.6 ± 1.6 (controls 57.1 ± 0.9), on the PASAT-3 — 30.3 ± 1.8 (controls 56.8 ± 0.5), the evaluation score on the MoСA was 22.4 ± ± 0.5 points compared to the control group (28.4 ± 0.2 points). The conducted correlation analysis revealed statistically significant negative correlations in the corpus callosum (MoCA: r = –0.255; SDMT: r = –0.263; PASAT-3: r = –0.171; p < 0.05) and in the brainstem (MoCA: r = –0.191; SDMT: r = –0.209; PASAT-3: r = –0.214; p < 0.05). The results of the analysis of variance confirmed the correlations described above between the localization of brain lesions and the results of neuropsychological testing and revealed statistically significant differences in the scores on the MoCA and SDMT depending on the localization of lesions (MoCA: F(14, 57) = 5.052, p < 0.001; SDMT: F(14, 57) = 2.609, p < 0.05). Conclusions. Patients with relapsing-remitting multiple sclerosis quite often have cognitive impairment, which is confirmed by the results of neuropsychological testing. Correlation analysis revealed a significant negative relationship between the localization of foci in the corpus callosum and the brainstem and cognitive decline according to the results of tests (MoCA, SDMT, PASAT-3). The results of our study confirm the presence of structural and functional connections between the localization of focal brain lesions and the development of cognitive disorders, which has important diagnostic and prognostic value.