Age of onset as a moderator of cognitive decline in pediatric-onset multiple sclerosis.

Cognitive impairment is often reported in pediatric-onset multiple sclerosis (MS). Using serial cognitive data from 35 individuals with pediatric-onset MS, this study examined how age at disease-onset and proxies of cognitive reserve may impact cognitive maturation over the course of childhood and adolescence. Neuropsychological evaluations were conducted at baseline and up to four more assessments. Of the 35 participants, 7 completed only one assessment, 5 completed two assessments, 13 completed three assessments, 10 completed four or more assessments. Growth curve modeling was used to assess longitudinal trajectories on the Trail Making Test-Part B (TMT-B) and the Symbol Digit Modalities (SDMT; oral version) and to examine how age at disease onset, baseline Full Scale IQ, and social status may moderate rate of change on these measures. Mean number of evaluations completed per patient was 2.8. Younger age at disease onset was associated with a greater likelihood of cognitive decline on both the TMT-B (p=.001) and SDMT (p=.005). Baseline IQ and parental social status did not moderate any of the cognitive trajectories. Findings suggest that younger age at disease-onset increases the vulnerability for disrupted performance on measures of information processing, visual scanning, perceptual/motor speed, and working memory. Proxies of cognitive reserve did not protect against the progression of decline on these measures. Young patients with MS should be advised to seek follow-up cognitive evaluation to assess cognitive maturation and to screen for the potential late emergence of cognitive deficits. (JINS, 2014, 20, 1-9).