Definitions
Dissemination in Space (DIS)
Evidence of MS-related lesions in at least two out of five predefined CNS topographies on MRI:
periventricular, juxtacortical/cortical, infratentorial, spinal cord, and optic nerve.
Dissemination in Time (DIT)
Evidence that CNS lesions have occurred at different points in time, demonstrated by the presence of new or enlarging T2 lesions, simultaneous enhancing and non-enhancing lesions, or specific paraclinical markers.
Optic Nerve Involvement
Structural or functional evidence of demyelination affecting the optic nerve, assessed by optic nerve MRI, optical coherence tomography (OCT), and/or visual evoked potentials (VEP).
The optic nerve is included as a fifth topography for DIS in the 2024 criteria.
Central Vein Sign (CVS)
An MRI biomarker defined by the presence of a small vein running centrally through a white matter lesion on susceptibility-based MRI sequences, reflecting the perivenular nature of MS pathology.
CVS-Positive Lesion
A white matter lesion in which a central vein is clearly visualized according to standardized radiological criteria, typically on T2*-weighted or susceptibility-weighted imaging (SWI).
Paramagnetic Rim Lesion (PRL)
A chronic active MS lesion characterized by a hypointense rim on susceptibility-based MRI, reflecting iron-laden microglia/macrophages at the lesion edge and ongoing inflammatory activity.
Susceptibility-Based MRI
A group of MRI techniques sensitive to magnetic susceptibility differences in tissue, enabling visualization of structures related to iron deposition or venous anatomy.
Perivenular Pathology
A pathological pattern in which inflammatory demyelination develops around small veins, reflecting a hallmark feature of MS lesion formation.
Visual Pathway Integrity
The functional and structural preservation of afferent visual pathways, including retinal, optic nerve, and post-chiasmal components.
