Peculiarities of an assessment of a cognitive efficacy in multiple sclerosis

Abstract

A key cognitive deficit in multiple sclerosis (MS) is a poor efficacy of the information processing, with working memory impairments and a decreased speed of the information processing as components of formation of this poor efficacy. Despite of a sufficient number of single cognitive tests and test batteries, there are still essential knowledge gaps and methodological limitations connected with understanding and measurements of the cognitive deficit in MS. To study real reasons of changes of the cognitive efficacy in MS, a neurocognitive testing with the original computerized Set for Assessment of Cognitive Capacity and Switchability (сSACCAS), an assessment of levels anxiety/depression, and an assessment of level of fatigue were performed for 25 patients with MS (including 17 female patients) (with a mean age of 34.14 ± 2.13 years old) and 25 practically healthy persons (including 15 females) (with a mean age of 31.80 ± 2.60 years old). To determine neurophysiological correlates of the cognitive functioning, an examination of cognitive evoked potentials (CEP) was performed. An investigation of the distribution density of results of the MS patients’ testing defined 3 groups among them. These groups had differences on the time of performing of test tasks, the “real mistake ratio”, switchability, parameters of N2- and P3-components of CEP, a localization of a maximal P3 peak. The motor reaction speed was more connected with the attention and the information processing speed, than with a visual-spatial orientation, whereas the fatigue more influenced on the speed of comparison and decision making, than on the attention. In 44 % of cases, the time of reply in tests were increased by a slowing down of assessment of a stimulus modality; in 24 % of cases, a long delay of the reply was connected, besides of a low speed of cognitive processes, with impairments of a working memory. The results obtained confirmed a significance of an integrated approach to understand reasons of changes of the cognitive efficacy and to assess adequately cognitive impairments in MS. Key words: neurocognitive computerized tests, cognitive efficacy, cognitive evoked potentials, multiple sclerosis