Baseline MRI & Initial Lesion Count
First scan anchors every future comparison — a lesion census at time zero.
- 5–20: Typical baseline T2 lesions (at first diagnosis)
- 1.5–3T: MRI field strength (standard clinical)
- FLAIR: Key sequence (suppresses CSF signal)
- 6–12 mo: Rescan interval (guideline standard)
Why a baseline matters
Sets the reference count and volume future scans are compared against.
One scan alone cannot show activity — comparison is everything.
T2/FLAIR lesion detection
Bright periventricular spots mark areas of past or current demyelination.
Standardized protocol
Same scanner, slice angle, and sequence improve reliable lesion tracking.
Follow-Up MRI at 6 Months
A second scan reveals whether new lesions accumulated since baseline.
- 6 mo: Follow-up window (first comparison point)
- 1+: New lesion = activity (any new T2 spot counts)
- mm³: Volumetric change tracked (total burden growth)
- ~10:1: Subclinical lesion rate (vs relapses (MRI vs clinic))
Image co-registration
Baseline and follow-up scans align to spot genuinely new lesions.
Cumulative lesion load
Total T2 count/volume climbs — a running ledger of disease burden.
Subclinical activity
Most new lesions cause no symptoms yet still reflect ongoing disease.
Gadolinium-Enhancing Lesions
Contrast dye leaks through a broken blood-brain barrier into active lesions.
- ~3–4 wk: Gd enhancement duration (per active lesion)
- Active: BBB disruption signals (inflammation ongoing)
- Gd+: T1 post-contrast bright spot (marks acute lesion)
- weeks: Enhancement fade (lesion then quiets)
Blood-brain barrier breakdown
Inflammation opens the barrier, letting gadolinium dye leak in.
Gd+ as an activity marker
Enhancing lesions mark currently active, not just old, disease.
Time-limited signal
Enhancement typically resolves within weeks as inflammation settles.
New Lesion Activity Since Baseline
Combined new T2 and Gd findings flag breakthrough disease on therapy.
- 1+ new: Breakthrough definition (T2 or Gd+ lesion)
- New lesion: Therapy review trigger (prompts re-evaluation)
- CUA: Combined unique lesions (new T2 + new Gd, no double count)
- More sensitive: MRI vs relapse detection (MRI wins)
Breakthrough disease activity
New lesions despite treatment suggest the current therapy is underperforming.
Combined unique active lesions
CUA metric merges new T2 and Gd+ counts without double-counting.
Clinical decision point
Repeated new activity often prompts a switch to a stronger therapy.
NEDA — No Evidence of Disease Activity
NEDA means no new lesions, no relapses, no disability progression.
- 3: NEDA-3 criteria (MRI + relapse + disability)
- Brain atrophy: NEDA-4 adds (volume loss rate)
- ~40–60%: 2-year NEDA on therapy (high-efficacy DMTs)
- Switch DMT: Non-NEDA action (escalate therapy)
Defining NEDA
No new/enlarging T2, no Gd+, no relapse, no confirmed disability change.
Treat-to-target strategy
Clinicians increasingly aim for NEDA rather than just fewer relapses.
When NEDA fails
Lesion accumulation without NEDA prompts considering a therapy switch.