Identification and Clinical Impact of Multiple Sclerosis Cortical Lesions as Assessed by Routine 3T MR Imaging

It is possible that many if not most clinical symptoms of multiple sclerosis patients are due to plaques in the gray matter and not in the white matter as commonly believed (remember that myelinated fibers are found in cortical and deep gray matter). Could it be that because cortical plaques are not routinely seen at 1.5T we do not think about this issue? Here, the authors studied 26 patients with 3D FLAIR and inversion recovery spoiled gradient recalled sequences at 3T and found cortical plaques in 24 of them. The volume and load of these cortical plaques correlated with those seen in white matter. Cortical lesions also correlated with verbal learning test disability scale results better than white matter lesion load. Conclusion: routinely detectable cortical lesions were related to physical disability and cognitive impairment. BACKGROUND AND PURPOSE: Histopathologic studies have reported widespread cortical lesions in MS; however, in vivo detection by using routinely available pulse sequences is challenging. We investigated the relative frequency and subtypes of cortical lesions and their relationships to white matter lesions and cognitive and physical disability. MATERIALS AND METHODS: Cortical lesions were identified and classified on the basis of concurrent review of 3D FLAIR and 3D T1-weighted IR-SPGR 3T MR images in 26 patients with MS. Twenty-five patients completed the MACFIMS battery. White matter lesion volume, cortical lesion number, and cortical lesion volume were assessed. RESULTS: Overall, 249 cortical lesions were detected. Cortical lesions were present in 24/26 patients (92.3%) (range per patient, 0–30; mean, 9.6 ± 8.8). Most (94.4%, n = 235) cortical lesions were classified as mixed cortical-subcortical (type I); the remaining 5.6% (n = 14) were classified as purely intracortical (type II). Subpial cortical lesions (type III) were not detected. White matter lesion volume correlated with cortical lesion number and cortical lesion volume (rS = 0.652, rS = 0.705, respectively; both P < .001). After controlling for age, depression, and premorbid intelligence, we found that all MR imaging variables (cortical lesion number, cortical lesion volume, white matter lesion volume) correlated with the SDMT score (R2 = 0.513, R2 = 0.449, R2 = 0.418, respectively; P < .014); cortical lesion number also correlated with the CVLT-II scores (R2 = 0.542–0.461, P < .043). The EDSS scores correlated with cortical lesion number and cortical lesion volume (rS = 0.472, rS = 0.404, respectively; P < .05), but not with white matter lesion volume. CONCLUSIONS: Our routinely available imaging method detected many cortical lesions in patients with MS and was useful in their precise topographic characterization in the context of the gray matter−white matter junction. Routinely detectable cortical lesions were related to physical disability and cognitive impairment.