MS Relapse vs. Pseudorelapse: What Triggers Each and When Steroids Are Needed

What’s Really Happening When Your MS Symptoms Flare Up?

If you have multiple sclerosis, you’ve probably felt it: sudden weakness, blurry vision, numbness, or a spike in fatigue. Your first thought? Relapse. But what if it’s not? What if your body isn’t having a new attack - it’s just reacting to something else?

Up to 25% of symptom flare-ups in MS aren’t true relapses at all. They’re called pseudorelapses - temporary worsening of old symptoms caused by external triggers, not new nerve damage. Mistaking one for the other can mean getting unnecessary steroids, facing side effects like high blood sugar or mood swings, and missing the real fix.

Here’s how to tell the difference - and what to do next.

True MS Relapse: New Damage, New Symptoms

A true MS relapse happens when your immune system attacks the myelin sheath around nerves in your brain or spinal cord. This causes new inflammation, new lesions, and new neurological symptoms - or a significant worsening of existing ones.

The key? Duration and no trigger. If your symptoms last more than 48 hours and there’s no clear cause like fever, infection, or heat, it’s likely a true relapse. Common signs include:

• Sudden loss of balance or coordination
• New weakness in one leg or arm
• Blurred or double vision (not just heat-related)
• Loss of bladder or bowel control
• Severe numbness or tingling that doesn’t fade

On an MRI, you’ll see new or active lesions - areas where the immune system has attacked. These show up as bright spots on contrast scans. That’s the smoking gun.

True relapses can leave lasting damage. Even if you recover, some nerve function may never fully return. Each relapse adds up over time, especially in the early years of MS.

Pseudorelapse: The Body’s False Alarm

A pseudorelapse feels just as real - but it’s not new damage. It’s your damaged nerves struggling to send signals because something in your body is throwing them off.

Think of it like a frayed wire. Normally, it still works. But when it gets too hot, too tired, or too stressed, it shorts out. Turn off the trigger, and it works again.

Common triggers include:

• Heat - Hot showers, summer weather, fever. Up to 80% of people with prior optic neuritis get Uhthoff’s phenomenon - vision blurs when body temperature rises.
• Urinary tract infections (UTIs) - The #1 trigger. In one study, 67% of pseudorelapses were linked to UTIs.
• Fever - Even a mild 100.4°F spike can make symptoms worse.
• Stress - Emotional or physical burnout can temporarily overload your nervous system.
• Exhaustion - Too much activity, poor sleep, or dehydration.

Here’s the big difference: pseudorelapse symptoms fade fast - usually within hours or a day - once the trigger is gone. No new lesions show up on MRI. No new damage is done.

Steroids: When They Help - and When They Don’t

High-dose IV methylprednisolone is the standard treatment for true relapses. It reduces inflammation, speeds up recovery, and helps you get back on your feet faster - especially if symptoms affect walking, bladder control, or vision.

Studies show about 70-80% of people see improvement with steroids. But only 45-55% fully recover. And the side effects? Real.

• Insomnia in 40%
• Mood swings or anxiety in 30%
• High blood sugar in 25%
• Increased risk of infection

Now, here’s the problem: steroids do nothing for pseudorelapses. No inflammation means no target for the drug. Giving steroids in these cases doesn’t help - it just risks harm.

Research shows 30-40% of pseudorelapses are mistakenly treated with steroids. One Reddit user, a nurse with MS, reported seeing five patients in a year get IV steroids for UTI-triggered flare-ups. One developed steroid-induced psychosis and had to be hospitalized.

That’s not just unnecessary - it’s dangerous.

How to Know for Sure: The 3-Step Check

Don’t guess. Use this simple process:

1. Check duration. Did symptoms last less than 24 hours? Likely a pseudorelapse. More than 48? Could be a true relapse.
2. Rule out triggers. Did you have a fever? A UTI? A hot day? Take your temperature. Get a urine test. Check your blood sugar and sodium levels. These are quick, cheap, and critical.
3. Consider an MRI. If you’re still unsure, an MRI with contrast can show new lesions. No new lesions? Probably not a true relapse.

Many neurologists now use the MS-Relapse Assessment Tool (MS-RAT), which scores symptoms, duration, temperature, and function to give a probability of true relapse vs. pseudorelapse. It’s 92% accurate.

Who’s Most at Risk for Pseudorelapses?

It’s not random. People with:

• Longer disease duration (10+ years)
• Higher baseline disability
• History of optic neuritis (for Uhthoff’s phenomenon)
• Older age (over 55)

are more likely to experience pseudorelapses. Why? Because their nervous system has more damaged pathways. Even small stressors can overload them.

But here’s the catch: older patients with pseudorelapses sometimes don’t bounce back fully - not because of nerve damage, but because of deconditioning. After a week of weakness, they lose muscle tone. They don’t move as much. Recovery takes longer - even after the trigger is gone.

What to Do When It Happens

Don’t panic. Don’t rush to the ER for steroids.

For a suspected pseudorelapse:

• Cool down. Use cooling vests, cold drinks, air conditioning. For Uhthoff’s, symptoms often vanish in under two hours.
• Treat the trigger. Antibiotics for a UTI. Rest for exhaustion. Hydration for dehydration.
• Track it. Keep a simple log: date, symptoms, temperature, possible triggers, how long it lasted. This helps your neurologist spot patterns.

For a true relapse:

• Call your neurologist ASAP.
• Don’t wait to see if it gets worse.
• Be ready to discuss functional impact - can you walk? Use your hands? Control your bladder?

Why This Matters Beyond the Symptoms

Misdiagnosing a pseudorelapse as a true relapse doesn’t just waste time and money - it harms your body.

The National MS Society estimates that unnecessary steroid treatments for pseudorelapses cost the U.S. healthcare system over $12 million a year. That’s millions in IV drugs, hospital visits, and side effect management.

But the real cost? Trust. When patients get steroids they don’t need, they start to doubt their doctors. When they’re told it’s "just stress" and their symptoms don’t improve, they feel dismissed.

Accurate diagnosis builds confidence - in your care, in your body, and in your ability to manage MS.

What You Can Do Today

You don’t need to wait for your next appointment to take control.

• Download a symptom tracker app or use a notebook. Record triggers every time symptoms flare.
• Keep a thermometer and urine dipsticks at home. Test at the first sign of trouble.
• Ask your neurologist: "Can we review my relapse history and triggers together?"
• If you’ve had a pseudorelapse before, tell your ER doctor or primary care provider. Many don’t know the difference.

MS is complex. But knowing the difference between a relapse and a pseudorelapse gives you power - not just over your symptoms, but over your treatment.