Author Of 1 Presentation
P0823 - Resting state functional connectivity correlates of executive function in patients with multiple sclerosis (ID 1084)
The functional substrates of deficits of executive function (EF), a relevant disabling symptom in MS patients, have been scarcely investigated.
To investigate changes of resting state (RS) functional connectivity (FC) in patients with MS and their correlation with neuropsychological measures related to EF.
High-resolution T1-weighted and RS functional MRI (fMRI) scans were acquired from 116 MS patients and 65 matched healthy controls (HC). All subjects underwent a neuropsychological evaluation, including the computerized version of the Wisconsin Card Sorting Test (WCST), a multidimensional EF assessment. MS patients also underwent a clinical evaluation, including the expanded disability status scale (EDSS). RS FC was assessed using a seed-voxel correlation analysis. Seed regions relevant for EF were derived from the literature: left (L) inferior parietal sulcus (IPS), L frontal pole (FP) and right (R) cerebellum (Crus I and II). We used SPM and voxel-wise models to compare RS FC between MS patients and HC within the identified networks. Then, associations between RS FC and age- and education-corrected WCST scores and EDSS were evaluated.
Twenty-five (21.5%) MS patients failed the WCST. Compared to HC, MS patients showed significantly decreased RS FC of the L IPS with bilateral middle frontal, L middle temporal and L cerebellar regions, as well as increased RS FC of the L IPS with bilateral thalami. MS patients also exhibited decreased RS FC between the L FP and superior parietal regions. A widespread RS FC decrease was found in MS vs HC between the R Crus I/II and bilateral cerebellar regions and fronto-parietal cortices. Significantly increased RS FC was finally detected between the R Crus I/II and the bilateral orbitofrontal cortex. In MS patients, significantly increased RS FC between the R Crus I/II regions and the orbitofrontal cortex was associated with better performance at the WCST (r=range 0.19-0.27, p=range 0.03-0.003). Conversely, decreased fronto-cerebellar and parieto-cerebellar RS FC was correlated with higher EDSS score (r=range -0.19 to -0.35, p=range 0.03-<0.001).
In an MS group relatively spared by relevant EF deficits, increased RS FC strength in EF-related functional networks was detected. The association between increased RS FC and better WCST scores suggests a compensatory role of detected RS FC abnormalities in these patients.
Presenter Of 1 Presentation
P0830 - Unraveling the substrates of cognitive impairment in multiple sclerosis: the contribution of a multiparametric structural and functional MRI approach (ID 1081)
Cognitive impairment (CI) affects up to 70% of multiple sclerosis (MS) patients. Although several magnetic resonance imaging (MRI) correlates of CI have been suggested, their relative contribution to explain CI requires further investigation.
To evaluate the combined contribution of white matter (WM) lesions, gray matter (GM) atrophy and resting state (RS) functional (f) MRI abnormalities in explaining CI in a large cohort of MS patients.
Brain 3T dual-echo, 3D T1-weighted and RS fMRI scans were acquired from 100 healthy controls (HC) and 276 MS patients. All MS patients underwent the Rao’s battery. CI was defined by ≥2 tests with a z-score<-1.5. Distribution of brain WM lesions, GM atrophy and RS functional connectivity (FC) abnormalities within the default mode (DMN) and salience (SN) networks were compared between HC and MS patients at a voxel level. Using sex-, age- and phenotype-adjusted stepwise logistic regression models, the role of WM lesions (model 1), GM atrophy (model 2), RS FC (model 3) and their combination (model 4) in explaining CI was investigated. Model performances were assessed by the area under the curve (AUC).
Eighty-three MS patients had CI. In model 1, lesions in left (L) superior longitudinal fasciculus (SLF) (odds ratio [OR]=1.84), L medial lemniscus (OR=1.79) and L inferior longitudinal fasciculus (OR=1.57) predicted CI (p≤0.009). In model 2, L precuneus (OR=0.52) and L caudate (OR=0.56) volumes predicted CI (p≤0.007). In model 3, increased RS FC in L caudate (DMN) (OR=1.77) and decreased RS FC in right (R) thalamus (DMN) (OR=0.66) and L inferior frontal gyrus (IFG) (SN) (OR=0.68) predicted CI (p≤0.02). In model 4, R middle cerebellar peduncle (OR=2.05) and L SLF (OR=1.84) lesions, L precuneus atrophy (OR=0.46), increased RS FC in L caudate (DMN) (OR=1.64), and decreased RS FC in L IFG (SN) (OR=0.64) predicted CI (p≤0.02). Compared to demographic and clinical variables only (AUC=0.73), the separate models performed significantly better (AUC=0.82, 0.81 and 0.80, respectively, p≤0.003), with model 4 having the best performance (AUC=0.86, p<0.001).
The combination of multiparametric MRI techniques contributes to better understand the structural and functional substrates of cognitive dysfunction in MS patients. The accumulation of focal WM lesions and GM atrophy in strategic brain regions together with maladaptive functional mechanisms explains CI in MS.