Subpial demyelination in the cerebral cortex of multiple sclerosis patients.

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.