Patterns of cognitive impairment in relapsing-remitting multiple sclerosis and their relationship to neuropathology on magnetic resonance images

Several reviews (J. M. Peyser and C. M. Poser, 1986; S. M. Rao, 1986) have suggested that multiple sclerosis (MS) results in cognitive impairment in learning and memory, abstract reasoning, information-processing efficiency, and often visual-spatial ability. MS patients may undergo idiosyncratic cognitive changes dependent on the site of white matter lesions. In the present study, researchers used cluster analysis on the neuropsychological data from a group of mildly disabled relapsing-remitting MS patients (n = 177) and a well-matched control group (n = 89). In those MS patients identified with unequivocal cognitive impairment, the majority clustered into groups with a specific deficit in 1 or 2 areas of cognitive functioning, with normal performance in others. On magnetic resonance imaging, an association Was obtained between 2 lesion sites and 2 cognitive tests. Impairment in visual-spatial ability, as assessed by the Benton Visual Retention Test, was associated with lesions in the genu of the corpus callosum (CC) and with more lesions throughout the CC. Impaired performance on Paired Associates, a test of learning and memory, was associated with a lesion in the deep white matter of the left parietal lobe. The findings support the hypothesis that MS results in multiple patterns of cognitive impairment that depend on the individual placement of white matter lesions.