Abstract
Multiple Sclerosis (MS) is a chronic inflammatory/demyelinating and neurodegenerative disease of the central nervous system (CNS). Most patients experience a relapsing-remitting (RR) course, while about 15–20% of patients experience a primary progressive (PP) course. Cognitive impairment affects approximately 40–70% of all MS patients and differences in cognitive impairment between RR-MS and PP-MS have been found. We aimed to compare RR-MS and PP-MS patients in terms of cognitive performance, and to investigate the MRI correlates of cognitive impairment in the two groups using measures of brain volumes and cortical thickness. Fifty-seven patients (42 RR-MS, 15 PP-MS) and thirty-eight matched controls underwent neuropsychological (NP) testing and MRI. PP-MS patients scored lower than RR-MS patients on most of the NP tests in absence of any specific pattern. PP-MS patients showed significantly lower caudate volume. There was no significant difference in MRI correlates of cognitive impairment between the two groups except for a prevalent association with MRI measures of cortical GM injury in RR-MS patients and with MRI measures of subcortical GM injury in PP-MS patients. This suggests that although cognitive impairment results from several factors, cortical and subcortical GM injury may play a different role depending on the disease course.
Highlights
Multiple Sclerosis (MS) is a chronic inflammatory/demyelinating and neurodegenerative disease of the central nervous system (CNS)
Our study aimed at exploring potential differences in cognitive performance and MRI correlates of cognitive deficits in patients with RR-MS and patients with primary progressive (PP)-MS who are Overall FAS CLVT* Symbol Digit Modalities Test (SDMT) DKEFS-I DKEFS-IS PASAT
Normalized volumes are in mL, cortical thickness is in mm, subcortical volume is in mm3. * p < 0.05 when compared with control group ** p < 0.01 when compared with control group *** p < 0.001 when compared with control group # p < 0.05 when compared with RR-MS group doi:10.1371/journal.pone.0129380.t003
Summary
Multiple Sclerosis (MS) is a chronic inflammatory/demyelinating and neurodegenerative disease of the central nervous system (CNS). A recent MRI study performed at 7 Tesla reported no differences in lesional morphological features (count, preferred location, type, hypointense rim) between RR-MS and PP-MS [8] Both pathological and MRI studies have shown that cortical demylination and gray matter (GM) atrophy are more prominent in PP-MS than in RR-MS [9,10]. MRI measures of cortical lesions count, cortical thinning and gray matter atrophy are found to be associated with cognitive impairment in MS [11,12,13,14,15,16] Most of these studies are directed to the investigation of MRI correlates of cognitive impairment in RR-MS patients only [15,17]. We hypothesize that cognitive impairment would have different MRI correlates in RR-MS and PP-MS patients
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