Cortical/subcortical disease burden and cognitive impairment in patients with multiple sclerosis

BACKGROUND AND PURPOSE: We assessed whether the extent of macro- and micros copic disease in the cortical and subcortical brain tissue, as revealed by MR and magnetization transfer (MT) imaging, correlates with cognitive dysfu nction in patients with multiple sclerosis (MS), METHODS: Dual-echo rapid acquisition with relaxation enhancement (RARE), fa st fluid-attenuated inversion recovery (fast-FLAIR), T1-weighted, and MT MR images of the brain were obtained from 16 MS patients with cognitive impai rment and from six without. Impaired and unimpaired patients were similar a cross demographic and other disease-related variables, Total and cortical/s ubcortical lesion loads were assessed using RARE, fast-FLAIR, and T1-weight ed sequences. In each patient, cortical/subcortical disease was also assess ed by means of MT ratio (MTR) histographic analysis. RESULTS: All the impaired patients had multiple hyperintense lesions in the cortical/subcortical regions on both RARE and fast-FLAIR images; two unimp aired patients had such lesions on the RARE images and four had them on the fast-FLAIR images. Total and cortical/subcortical RARE/fast-FLAIR hyperint ense and T1 hypointense lesion loads were significantly greater in the grou p of cognitively impaired patients. Patients with cognitive deficits also h ad significantly lower MTR histographic values for all the variables, A mul tivariate regression model showed that average cortical/subcortical brain M TR was the only factor that was significantly associated with cognitive imp airment. CONCLUSION: The extent and severity of MS disease in the cortical and subco rtical regions significantly influence the cognitive functions of MS patien ts. MTR histographic findings suggest that subtle changes undetectable by c onventional imaging are also important in determining MS cognitive decline.