Relapses, also known as exacerbations, flares, or attacks, are common in multiple sclerosis. In fact, in the most common type of multiple sclerosis (MS), relapsing-remitting MS (RRMS), relapses, or periods when new symptoms occur or old ones recur or worsen, are followed by remissions, or periods of partial or complete recovery, according to the National Multiple Sclerosis Society (NMSS).

And just as the symptoms of MS can vary from person to person, the experience of and recovery from an exacerbation is also unique for everyone.

Even though there is a wide spectrum of possible symptoms, severity, and duration in an MS flare, knowing what causes an exacerbation and what to expect if you have one can help you navigate the unpredictability of the disease.

What Causes an MS Relapse?

In multiple sclerosis, the immune system mistakenly attacks the central nervous system (the brain and spinal cord, as well as the optic nerves), explains the NMSS. This causes damage to the myelin, or the insulating layer of protein and fat that protects nerve fibers, which in turn disrupts signals to and from the brain and causes the signs and symptoms of MS.

In RRMS, inflammatory attacks on the myelin, as well as the nerve fibers, leads to small, localized areas of damage, per the NMSS. Because the location of the damage differs with every person and every attack, no two people have exactly the same symptoms.

But exactly what triggers the inflammation that causes the attack can be difficult to pinpoint, says Tanuja Chitnis, MD, director of the Mass General Brigham Pediatric MS Center at the Mass General Hospital for Children in Boston.

One misconception is that vaccines increase the risk of an MS flare.

“The evidence is strong that vaccinations do not trigger flares,” Dr. Chitnis says.

What Does an MS Flare Feel Like?

“Symptoms of an MS flare generally come on over the course of several days,” explains Chitnis.

According to the NMSS, the most common symptoms reported in RRMS include:

Episodes of fatigue
Numbness
Vision problems
Spasticity or stiffness
Bladder and bowel problems
Problems with cognition (learning, memory, information processing)

Relapses can be very mild, or severe enough to affect your ability to function. The severity of flares varies from person to person and from flare to flare.

How Long Do MS Relapses Last?

To be considered a true relapse, the flare-up of symptoms must occur at least 30 days after your most recent exacerbation, and the new, recurring, or worsening symptoms must last for at least 24 hours, notes the NMSS. The relapse also must not have been triggered by an infection, or another cause, such as stress.

Relapses typically last from a few days to several weeks or months.

How Often Do MS Relapses Occur?

While the frequency of relapses vary from person to person, a research article published in Multiple Sclerosis and Related Disorders in 2018 looked at data from about 5,300 people with MS who responded to the Multiple Sclerosis in America 2017 online survey.

The researchers found that, in the two years preceding the survey, 73.1 percent of respondents had experienced a relapse, with a median number of two relapses, with some having more than two relapses in one year.

Additionally, the most common relapse symptoms that respondents experienced were fatigue (77.4 percent), numbness/tingling (70 percent), and walking or balance issues (68.8 percent).

It’s common to have fewer MS relapses over time, with the disease becoming more progressive, according to the NMSS.

What Is a Pseudoexacerbation?

A brief flare-up of symptoms that comes and goes in less than 24 hours is not technically considered a relapse, per the NMSS.These mini-flares are called pseudoexacerbations, and they can resolve without any treatment.

Pseudoexacerbations can be caused by fatigue, overexertion, fever, infection (urinary tract infections), and exposure to heat and humidity.

Treatment for MS Flares

Not all relapses require treatment. Mild sensory changes, such as numbness and pins-and-needle sensations, or episodes of fatigue that don’t significantly impact your daily life, often improve without intervention, notes the NMSS.

Steroids

For more severe exacerbations that affect mobility, safety, or overall ability to function, such as loss of vision, severe weakness, or poor balance, most neurologists recommend a short course of high-dose corticosteroids to reduce inflammation and shorten the duration of the flare. The most common form of treatment for these flares is a three- or five-day course of intravenous methylprednisolone (Solu-Medrol) or oral prednisone (Deltasone).

Recent studies have shown that oral steroids may be a less costly and more convenient way to treat relapses, compared with intravenous (IV) delivery. In a study published in 2018 in the European Journal of Hospital Pharmacy, oral steroids were found to be just as effective as IV steroids, and 79 percent of patients preferred taking the medication orally.

While steroids reduce inflammation and relieve symptoms, they do not reverse the damage to the nerves.

Other treatments for MS relapses include:

Plasmapheresis (Plasma Exchange) This can be used as a second-line therapy if a person can’t tolerate steroids or if steroids have been tried and haven’t been effective in treating the relapse. In this medical procedure, also known as apheresis, plasma exchange, or PLEX, whole blood is removed from a large vein and separated into the cellular components and plasma, according to the Neurological Institute at Cleveland Clinic in Ohio.

The removed plasma is discarded and replaced with colloid fluid that’s a combination of human serum albumin or fresh frozen plasma, which is then combined back with the cellular components and returned to the patient.

A study published in Multiple Sclerosis and Related Disorders in 2018 found that plasma exchange was relatively safe and effective, with complete recovery in 41.3 percent of patients and partial recovery in 39.1 percent.

Intravenous Immunoglobulin (IVIG) This procedure may be considered for relapses during pregnancy (when steroids should be avoided, if possible), and it may decrease the risk of postpartum relapses, per the NMSS. IVIG is also sometimes used as a second- or third-line treatment if a person doesn’t respond to or can’t tolerate steroids and plasmapheresis.

Immunoglobulin is the term for the fraction of plasma that contains antibodies. In IVIG, a mixture of antibodies is delivered intravenously with the aim of treating the relapse by stimulating some parts of the immune system while suppressing other parts.

H.P. Acthar Gel Also know as repository corticotropin injection, this is another second-line therapy, which was found to be a more effective alternative to steroids for treating flares compared with IVIG or plasmapheresis, according to a study published in 2019 in Neurology and Therapy and conducted by Mallinckrodt, the company that manufactures the gel.

Acthar stimulates the production of the steroid hormones cortisol, corticosterone, and aldosterone, which help the body respond to stress.

In the study, Acthar successfully treated MS relapses in 96.9 percent of patients, compared with 50.7 percent for plasmapheresis and 43.9 percent for intravenous immunoglobulin.

In an analysis sponsored by Mallinckrodt, Acthar was found to be more cost-effective than PLEX or IVIG, although all three therapies are considerably more expensive than steroid treatment. In a cost per response analysis, Acthar gel cost $141,970 and the other therapies cost an average of $253,331. Those costs don’t factor in medical insurance coverage, which would vary from person to person.

The Role of Disease-Modifying MS Drugs in Preventing Relapses

Disease-modifying therapies (DMTs) for MS aren’t used to treat flares, but some of the newer ones show promise at preventing them, says Bruce Bebo Jr., PhD, the executive vice president for research at the NMSS.

“Treatments seem to be getting better at decreasing the frequency of flares, the inflammation responsible for them, and the damage the flares cause to the body,” Dr. Bebo says.

Evidence supports the effectiveness of these medications, including a study that tracked the effectiveness of nine different oral and injectable DMTs, published online in 2017 in ClinicoEconomics and Outcomes Research. Investigators found that people who were adherent to the medications reduced the likelihood of relapse by 42 percent and hospitalization by 52 percent.

A poster presentation at the Consortium of Multiple Sclerosis Centers in 2019 also found increased incidence of relapses when people stopped taking their disease-modifying therapy for more than two months. That group had nearly 28 percent more relapses, 25 percent more emergency department visits, and 40 percent more hospitalizations, when compared with people who continued to take their medication.

Recovering From an MS Flare

During remissions, all symptoms may clear up, or some symptoms may be long-lasting or even permanent, notes the NMSS.

Younger people generally recover better from flares than older people, according to Chitnis.

Poor recovery from flares in the first five years following diagnosis could be a risk factor for developing early secondary-progressive MS, according to a study published in 2015 in Neurology.

A variety of types of rehabilitation specialists — including physical therapists, speech/language pathologists, occupational therapists, and cognitive remediation specialists — can play an important role in helping you regain physical and mental function after a flare.

Additional reporting by Becky Upham.

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