MRI correlates of cognitive dysfunction in multiple sclerosis patients.

Studies with conventional magnetic resonance imaging (MRI) support the hypothesis that cognitive impairment in multiple sclerosis (MS) patients is related with the lesion burden. Patterns of frontal lobe cognitive decline were also found to be related with the corresponding regional lesion load, although the total lesion load on T2-weighted MRI scans of the brain seems to be more relevant in determining frontal lobe deficits. Other non-conventional MRI techniques with a higher specificity to the heterogeneous substrates of MS pathology, such as the assessment of hypointense lesion load on T1-weighted scans and the histogram analysis of magnetisation transfer ratio (MTR) maps, have recently been applied to MS cognitive studies. Results from these studies suggest that three factors play a role in the pathogenesis of MS dementia: the burden of MS lesions, the severity of the pathological damage within individual lesions and that of the normal-appearing white matter.