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STUDIES: Cognition issues apparent in early multiple sclerosis

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  • STUDIES: Cognition issues apparent in early multiple sclerosis

    This disease aims to mess with us right from the start. Don't underestimate it. - D

    Brain compensatory mechanisms and cognition in early multiple sclerosis

    B. Audoin
    Aix-Marseille Université, CNRS, CRMBM UMR 7339, APHM, Pôle de Neurosciences Cliniques, Marseille, France

    Cognitive impairment is present from the very first stage of multiple sclerosis and is mainly characterized by deficits of speed of information processing, attention and executive functioning. At the early stage of the disease, cognitive impairment appears mainly underline by long distance connectivity disturbances secondary to early diffuse brain white matter damage. These structural damages may induce significant changes in the functional organization of the brain that may be related to adaptive or maladaptive reorganizations. Functional MRI studies have brought new insight into the better understanding of brain reorganization reactive to multiple sclerosis injury. First, task related fMRI studies demonstrated that patients at the early stage of the disease performing complex cognitive tasks showed higher activation in high level cortical regions included in the fronto-parietal network. In these regions, higher activation was associated with higher brain tissue damage but also with lower cognitive performances suggesting the existence of maladaptive or partially adaptive compensatory mechanisms. Recently, resting-state fMRI studies have provided new findings evidencing that connectivity strength was higher in the majority of brain cognitive networks in patients at the first stage of the disease. In addition, higher cognitive deficit were correlated with higher connectivity strength in the cognitive neuronal networks. Graph theoretical approach of resting state fMRI data evidenced that the modularity of the brain was increased at this stage of the disease especially in patients with cognitive impairment. These recent findings suggest that brain functional reorganization occurring in patients at the early stage of the disease is characterized by connectivity disturbances between brain specialized sub-networks increasing the modularity of the brain and a reactive enhancement of the connectivity strength into these sub-networks related to partially compensatory mechanisms. Reorganization into these sub-networks may be especially located in hub regions particularly involved in the connectivity between sub-networks.
    Dave Bexfield

  • #2
    Cognition in a newly diagnosed MS patient cohort

    K. O'Connell, M. Hutchinson, N. Tubridy, C. McGuigan
    Neurology Department, St Vincent's University Hospital, Dublin, Ireland

    Background: Cognitive impairment is common in MS with prevalence of up to 40% in clinically isolated syndrome (CIS) and early relapsing remitting MS (RRMS). The domains affected typically include information processing speed, episodic memory and executive function.
    Aims: To assess cognition in a cohort of newly diagnosed MS patients using the Brief International Cognitive Assessment in MS (BICAMS).

    Methods: During a prospective incidence study of MS in Ireland a sub-group of newly diagnosed patients (McDonald 2010) underwent a full assessment including BICAMS. Control participants, part of previous validation study, included unaffected relatives, spouses or carers accompanying patients to clinic. Impairment on individual tests was defined as -1.5 SD below reference group means and impairment on one or more tests was considered indicative of cognitive impairment.

    Results: 96 patients [80% women; mean age: 38 yrs (10.3); mean years of education: 13.5 yrs (2.7)] and 66 control participants [68% women; mean age 42.7 yrs (12.7); mean years of education: 14.1 yrs (3.2)] were recruited. 93% of patients were classified as RRMS. Mean age at diagnosis in RRMS and primary progressive MS (PPMS) groups were 37 (SD: 9.6) and 57 (SD: 7.7) yrs respectively. Mean time from diagnosis to review was 144 days (SD: 106). Using regression based norms derived from the control group 39% of patients fulfilled criteria for cognitive impairment. When this group was further subdivided into RRMS and PPMS, significant differences were seen between groups in SDMT (mean: 55 v 33,
    p< 0.001), CVLT2 (mean: 54 v 39, p< 0.001) and BVMT-R (mean 23 v 11, p< 0.001). 34% of the RRMS and 100% of the PPMS showed evidence of cognitive impairment.

    Conclusions: This study highlights the prevalence of cognitive impairment early in the disease course. The higher rate amongst PPMS likely represents older age at diagnosis and longer disease duration.
    Dave Bexfield