The extent and pattern of demyelination in the cerebral cortex was determined in 78 tissue blocks from the brains of 20 multiple sclerosis (MS) patients and 28 tissue blocks from 7 patients without neurological disease. Tissue blocks from 4 predetermined areas (cingulate gyrus, frontal, parietal, and temporal lobe) were studied, irrespective of macroscopically evident MS plaques. All tissue blocks contained cerebral cortex and periventricular and/or subcortical white matter. One hundred and nine demyelinating lesions were detected in the cerebral cortex, of which 92 (84.4%) were purely intracortical and 17 (15.6%) were lesions extending through both white and gray matter areas. In 5 of the 20 MS brains, subpial demyelination was extensive in the 4 widely spaced cortical areas studied, thus considered to represent a general cortical subpial demyelination. The percentage of demyelinated area was significantly higher in the cerebral cortex (mean 26.5%, median 14.1%) than in white matter (mean 6.5%, median 0%) (p = 0.001). Both gray and white matter demyelination was more prominent in the cingulate gyrus than in the other areas examined (p < 0.05). These results indicate that the cerebral cortex is likely to be a predilection site for MS lesions and identify general cortical subpial demyelination as a distinct pattern occurring in a significant subpopulation of MS patients.
