Is It an MS Relapse or Pseudoexacerbation?

Reviewed by: HU Medical Review Board | Last reviewed: May 2024 | Last updated: May 2024

Multiple sclerosis (MS) damages the nerves found in the brain, spinal cord, and optic nerve. This disrupts signals between the brain and the body, leading to a variety of symptoms. Some of the symptoms of MS are fatigue, vision problems, muscle weakness, and numbness or tingling.1

Sometimes, people with MS experience worsening neurological symptoms of MS. This can be due to an MS relapse or a pseudoexacerbation. A relapse and a pseudoexacerbation can seem similar. But their underlying causes are different.2,3

What is a pseudoexacerbation?

Pseudoexacerbation is a flare-up of chronic or prior MS symptoms. It can make your chronic MS symptoms worse or bring back MS symptoms you had with relapses in the past. But a pseudoexacerbation cannot cause neurological symptoms you have never had before. This is because a pseudoexacerbation is not caused by new damage to the nerves.2

Instead, a pseudoexacerbation is caused by temporary stress on your body. Nerves already damaged by MS are particularly prone to these stressors.2

What can cause a pseudoexacerbation?

Different stresses can cause pseudoexacerbations. For example:2,4

  • Infections, especially if they involve a fever, can result in pseudoexacerbations. Urinary tract infections are a common cause of MS pseudoexacerbations.
  • Heat can trigger a pseudoexacerbation. Activities that increase your body temperature can cause pseudoexacerbations. This includes things like taking a hot bath, exercising, or spending time in the sun.
  • Emotional stress like getting bad news can trigger pseudoexacerbations.
  • Physical stress like overworking or exerting yourself too much can lead to pseudoexacerbations.
  • Other medical conditions like thyroid disease, diabetes, or anemia can also be triggers.
  • Hormonal changes may also set off a pseudoexacerbation.
  • Vaccinations can result in pseudoexacerbations of MS.

Once the stress on the body goes away, the flare-up of MS symptoms resolves. This usually occurs within 24 hours.2

What are relapses?

A relapse is when you experience new symptoms of MS or your existing symptoms seem to get worse. A relapse happens when there is new damage to nerves in the central nervous system.3

Unlike pseudoexacerbations, the neurologic symptoms of relapses last for more than 24 hours. They typically last for a few days, weeks, or even months. Your symptoms are considered a new relapse if they start more than 30 days after your previous relapse and are not due to a pseudoexacerbation.3

What can cause a relapse?

An MS relapse can happen if the disease is uncontrolled. Things that can make it more likely for you to have a relapse include:5

  • Having a family history of MS relapses
  • Low levels of vitamin D
  • Hormonal changes especially during and after pregnancy

If you have MS, your chances of a relapse go down during a pregnancy. But the chance of relapse can increase after you give birth.5

How can pseudoexacerbations be prevented?

Not all pseudoexacerbations can be avoided. But there are several things you can do to help reduce your chance of getting one. For example:2

  • Avoid overdoing physical activity, such as difficult exercises or yard work, particularly during hot days.
  • Limit your time in hot environments, like saunas, hot tubs, or being outside during the hottest part of the day, if the heat affects you.
  • Practice good hygiene (like washing your hands) and avoid others who are sick to reduce your risk of getting an infection.

How can relapses be prevented?

Treatments are available that aim to stop the damage caused by MS relapses. These treatments are called disease-modifying therapies. They greatly improve quality of life by reducing the frequency of or preventing MS relapses. Talk to your doctor to find the right treatment for you.4

Dealing with a pseudoexacerbation or a relapse

If you experience a flare of symptoms, talk to your doctor to come up with a plan. Your doctor can help you find out whether your symptoms are due to a pseudoexacerbation or a relapse.

Depending on your symptoms, your doctor can make different suggestions. In the case of pseudoexacerbations, finding and removing the stress trigger will be most helpful. If your symptoms are getting worse due to a relapse, then your doctor may suggest treatments to stop MS from causing more damage to your nerves.2,4

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