Complex sentence: As mentioned prior, the MRI of an infected patient shows what appears to be a thickening of the cerebral cortex because of the tiny folds that aggregate causing a more dense appearance.
Split into simpler sentences: As mentioned prior, the MRI of an infected patient shows what appears to be a thickening of the cortex. They appear to have a thickening cerebral cortex because of the tiny folds that aggregate together causing a more dense appearance.