To test maturation effects on neuropsychological profiles and resting state (RS) functional connectivity (FC) in cognitive and motor networks of pediatric patients with multiple sclerosis (MS).

Clinical and cognitive features of pediatric MS patients differ from adults. The effect of brain maturation on RS FC and its possible interaction with cognitive features has never been studied.

Seventy-six pediatric MS patients underwent a neuropsychological assessment of Wechsler-Intelligence-Scales for Intelligent Quotient (IQ), Semantic/Phonemic Verbal Fluency Test (SVFT/PVFT), Symbol Digit Modalities Test (SDMT), Coding Design (CD) and Block Design (BD) subtests, Trial Making Test (TMT-A/B). In 58 right-handed MS patients and 22 matched healthy controls (HC), RS FC within basal ganglia, executive, language, sensorimotor, and default-mode networks was estimated. Maturation effects were tested by splitting pediatric MS in those below the age of 16 years (B16) (n=46) and those above or equal 16 years (A16) (n=30).

Most patients (81.6%) achieved IQ scores within or above average values (median IQ=97.5). The highest rate of failure was observed in CD (21.1%), TMT-B (15.8%), TMT-A (10.5%), and SDMT (9.2%). Compared to HC, pediatric MS patients showed reduced RS FC in all networks, mainly involving the caudate nucleus and its connections with cingulate, prefrontal, and sensorimotor cortices. This effect was particularly relevant in younger patients (B16), where reduced basal ganglia, language and executive RS FC was associated with poorer cognitive performances (r range=0.37/0.48), while reduced cingulate RS FC was associated with a lower IQ (r=0.36). In older patients (A16), reduced language and executive RS FC was correlated with lower IQ and CD, BD and PVFT/SVFT scores (r range=0.42-0.67). However, A16 patients also presented increased executive, default-mode and language RS FC vs HC, which was detrimental on performance at the same tests (r range=-0.39/-0.62).