Cognitive impairment in relapsing-remitting multiple sclerosis can be predicted by imaging performed several years earlier.

Cognitive deficits in multiple sclerosis (MS) are common and correlate with contemporary MRI brain abnormalities, particularly atrophy, but the ability of imaging early in the disease to predict later cognitive impairment remains to be determined. Thirty relapsing-remitting MS patients recruited within three years of the onset of the disease, and in whom MRI had been performed at baseline and a year later, were assessed neuropsychologically five years later. Imaging parameters accounting for significant variance in cognitive performance were identified using multiple regressions, once confounding variables were controlled. Patients performed significantly worse than expected on tests of attention/speed of information processing and half of them had experienced some decline in IQ in relation to premorbid estimates. The rate of global brain atrophy in the first year of the study accounted for significant variance in the overall cognitive performance, and in memory and attention/speed of information processing. Poor performance on attention tests was associated with high T1-weighted lesion volume and reduced magnetization transfer ratio (MTR) in normal-appearing white matter (NAWM). These results suggest that neuroaxonal loss was identified early in the disease, and its rate of progression, predicted cognitive impairment later in the disease. Neuroaxonal loss is likely to affect commissural and association fibres that subserve the cognitive processes impaired in MS.