On MRI, dissemination in time in MS is demonstrated by which finding?

• A. New lesion(s) appearing over time and/or gadolinium-enhancing lesions at different times.
• B. A single new lesion with no enhancement.
• C. Only T2 hyperintense lesions without enhancement.
• D. Diffuse brain atrophy without new lesions.

Answer: (A)

Dissemination in time means there is inflammatory demyelination occurring at more than one point in time. On MRI, this is shown when new lesions appear on follow-up imaging or when gadolinium-enhancing lesions are seen at different times, indicating active inflammation at separate time points. This combination demonstrates that MS activity has occurred at two distinct moments, which is why new lesions over time and/or gadolinium-enhancing lesions at different times is the best finding to confirm dissemination in time.

A single new lesion without enhancement does not prove time-separated activity, and isolated T2 lesions without enhancement or diffuse brain atrophy without new lesions do not demonstrate new inflammatory events over time.