What is an MS relapse?

Photo of a calendarRelapse Facts

  • Inflammation along nerves and myelin
  • New or worsening symptoms
  • Symptoms must be present for at least 24 to 48 hours, without a fever
  • Duration of a few days to a few months

Relapses, also referred to as exacerbations, attacks, flare-ups, episodes, or bouts, are experienced by most people diagnosed with multiple sclerosis (MS). When someone experiences a relapse, he or she may be having new symptoms or an increase in existing symptoms. Relapses occur with relapsing-remitting, progressive-relapsing, and sometimes secondary-progressive forms of MS. Relapses do not occur with primary-progressive MS, although individuals may experience day-to-day fluctuations in how they feel.

During a relapse, inflammation is occurring along the nerves and the myelin, causing people with MS to have a temporary worsening or recurrence of existing symptoms and/or the appearance of new symptoms. This can range from a few days in duration to a few months, followed by a complete or partial recovery (remission). Acute physical symptoms and neurological signs must be present for at least 24 hours, without any signs of infection or fever, before the treating physician may consider this type of flare-up to be a true relapse.

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