Inclusion | Lesions are hypointense relative to surrounding normal cortex |
They must involve the cortex in part or whole |
Caution | If small or ill-defined on a single slice, they must be visible on at least one other contiguous slice |
Equivocal lesions must be confirmed by retrospective detection of signal abnormality compatible with a lesion at the same location on the corresponding T2-weighted and/or FLAIR images |
Exclusion | Adjacent cerebrospinal fluid (partial volume effect), determined after reviewing adjacent PSIR slices and corresponding T2-weighted and FLAIR scans; especially likely in sulcal regions, at the temporal poles and near the vertex |
Artifacts, sometimes recognised by their symmetrical appearance (as also seen in DIR images)1 |
Vessels, which form very thin linear hypo-intensities, especially those that do not follow the direction of the cortical ribbon (cortical lesions may have a curvilinear or linear appearance, but they are less thin and invariably follow the direction of the cortical ribbon (supplementary figure 1)) |
Virchow-Robin spaces, which are prone to manifest in certain cortical regions27 28 (in particular, the insula and temporal poles), especially if linear and multiple, forming mesh-like or bundle-like appearances (these were seen in patients and controls (figure 1)) |