Acute Relapse Onset
A new lesion inflames. Function drops fast, EDSS spikes.
- ~6.0: Relapse EDSS peak (acute deficit)
- 1000 mg: Standard dose (IV methylprednisolone)
- 3–5 d: Course length (daily pulse)
- <72 h: Onset to peak (symptom escalation)
What triggers a relapse
Immune cells cross the blood-brain barrier, attack myelin locally.
Typical presentations
Optic neuritis, limb weakness, sensory loss, brainstem signs.
Why EDSS rises
New deficit adds disability points across functional systems.
Deficits worsening over 24–48h define a true relapse.
IV Methylprednisolone Pulse Begins
High-dose steroid infusion starts, day one of the course.
- ~1 h: Infusion time (per daily dose)
- Genomic: Mechanism class (anti-inflammatory)
- 1 of 5: Course day (pulse start)
- IV: Route (high-dose pulse)
Why IV, why high dose
Rapid, high tissue levels cross the leaky barrier fast.
Dosing pattern
1000mg once daily, typically for three to five days.
Molecular action
Glucocorticoid receptors dampen inflammatory gene expression.
Molecules diffuse straight to the inflamed lesion site.
Inflammation and Edema Recede
Swelling around the lesion falls as steroid levels build.
- ↓60–80%: Inflammation cut (by course end)
- Restored: Barrier effect (blood-brain barrier)
- Reduced: Edema (at lesion site)
- Suppressed: Immune infiltrate (locally)
Barrier repair
Tight junctions reseal, limiting further immune entry.
Edema resolution
Fluid clears, easing pressure on nearby axons.
Timing
Effect builds over the treatment days, not instantly.
More course-days completed, faster the swelling drops.
Neurological Recovery Unfolds
Conduction improves over days as inflammation subsides.
- 1–3 wk: Recovery window (post-treatment)
- Improving: Conduction (nerve signaling)
- Declining: EDSS trend (toward baseline)
- Partial repair: Myelin (remyelination)
Signal restoration
Less swelling lets axons conduct impulses again.
Recovery pace
Function returns gradually, days to a few weeks.
Steroids vs repair
Steroids speed recovery; true remyelination is slower.
Most improvement clusters in the first two weeks.
Relapse Resolution & Residual Deficit
EDSS improves a lot, but rarely all the way back.
- ~2.8: Residual EDSS (vs 2.0 baseline)
- Unchanged: Long-term course (disease trajectory)
- Substantial: Recovery (not always complete)
- Persists: Relapse risk (future episodes)
Incomplete return
A small residual deficit often remains after recovery.
Disability accrual
Repeated incomplete recoveries add up over time.
What steroids do not do
They treat the relapse, not the underlying disease course.
Disease-modifying therapy, not steroids, alters long-term risk.