MS cortical lesion or not?

Histopathologic analyses of postmortem brains from patients with multiple sclerosis (MS) have revealed that demyelinated cortical lesions are a common occurrence¹ and may account for a larger proportion of brain demyelination than white matter (WM) lesions.^2,–,4 Unlike WM lesions, cortical lesions are typically not revealed in vivo by conventional MRI (only 16% detected using fluid-attenuated inversion recovery [FLAIR] MRI³). As a result, our overall understanding of the incidence and role of cortical lesions in MS remains relatively poor.

Double inversion recovery (DIR) is an advanced MRI technique that improves visualization of the cortex by selectively suppressing both the CSF signal (as in FLAIR) and the normal WM signal, resulting in an image with hyperintense gray matter (GM) that is relatively noisy. In MS, DIR has revealed cortical foci that are hyperintense relative to surrounding normal-appearing GM, which are believed to be associated with demyelinated cortical lesions. Unfortunately, DIR is not reliably sensitive to subpial demyelination,^5,6 which represents the most common type of cortical demyelination in MS.^2,5 Despite this weakness, significant associations have been reported between DIR hyperintense cortical foci and disability in MS.^7,–,9

In practice, DIR is not standardized across imaging …