Dissemination in time in MS MRI is best evidenced by which finding?

• A. A single enhancing lesion on MRI.
• B. No change in lesion burden over time.
• C. Diffusion restriction in multiple areas.
• D. New lesions appearing over time and/or enhancement patterns indicating lesions separated in time.

Answer: (D)

Dissemination in time is shown on MRI by evidence that inflammatory lesions occurred at more than one point in time. The best way to demonstrate this is to see new lesions appearing on follow-up imaging, or to observe enhancement patterns that indicate lesions of different ages—some enhancing now (newer) and others non-enhancing (older). A single enhancing lesion only shows current activity and does not prove temporal spread. If the lesion burden remains unchanged, that argues against time dissemination. Diffusion restriction in multiple areas would more likely point to acute ischemia or another process, not the typical pattern used to establish lesions at different times. Therefore, new lesions over time and enhancement patterns showing lesions separated in time best demonstrate dissemination in time.