MS Relapse vs. Pseudorelapse

What is an MS Relapse vs. Pseudorelapse?

by Dr. James W. Stark

Patients with multiple sclerosis can exhibit worsened symptoms for a few different reasons. As physicians, we use certain terms differently from how they are used in regular speech and this can generate some confusion. For example, we reserve the term ‘relapse’ for new or worsened symptoms, which are due to new inflammatory MS activity in the brain or spinal cord. Usually, in a true ‘relapse’, the new symptoms manifest over a few hours or days and then plateau over a few days to weeks and then slowly improve over weeks to months. Steroids will often more rapidly improve this kind of worsening but steroids are actually not always necessary. Additionally, the vast majority of the time, this kind of worsening is associated with a change in your MRI.

Another way MS patients can experience worsening is called a pseudo-relapse. When physicians use this term, we are also referring to worsened neurologic symptoms; however the underlying cause of the worsening is not from new immune system activity or inflammation, but rather from the damage that has occurred from previous inflammation. This is very important because the treatment of this is generally not IV steroids, but determining what could be affecting the body to bring out ‘old’ symptoms. There are a number of stressors that can affect the body and MS in this manner. These include increased body temperature (from a fever, over-exercising, hot tub/sauna….), infection even in the absence of fever (the flu, urinary tract, sinus, and skin infections…), trauma, surgery, new medications, other medical conditions (high blood sugar in diabetics, for example) and psychological stress to name a few. A pseudo-relapse is not associated with an active MS lesion on MRI.

There are a variety of clues to help differentiate between a relapse and pseudo-relapse. Occasionally, however, it can be difficult to distinguish and further ancillary testing, such as an MRI, is required. Here are some quick tips to try to differentiate between the two.

(NOTE: Please call the office if you’re having new symptoms, this article is meant to be an educational tool only.)



If the worsened symptoms fluctuate, and especially if they resolve completely and then return, that is a good sign you may be experiencing a pseudo-relapse. This is one of the reasons that we rarely treat an MS relapse within 24 hours of symptom onset. Unlike a stroke, there is no evidence that rapid initiation of steroids is better and we want to judge whether symptoms may improve on their own.


Old MS Symptoms

The recurrence of old symptoms is more common in a pseudorelapse. Generally, MS does not result in repeated inflammation in the exact same part of the brain, so it is unlikely that patients will experience another true relapse exactly the way their previous relapses presented.



Localization is the term in neurology for identifying the location of the lesion within the brain or spinal cord based on the pattern of symptoms. Occasionally, neurologists can say for sure that there is no place that a lesion in the central nervous system could cause all of the current symptoms. This would indicate to us that another process (like infection, medication, stress) may be going on, which is causing the generalized worsening, rather than a new, active MS lesion.


Types of symptoms

Some worsened symptoms are much more likely to be a pseudorelapse than a relapse. These include sudden worsening of spasticity and pain, which are certainly seen in MS, but are rarely due to an acute relapse. As neurologists, we use all of these points to help us evaluate what is going on when a patient feels worse. We rely on your history, especially the time course and pattern of symptoms, and use the laboratory testing and MRI additionally when needed.


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