Most people with multiple sclerosis have a type of MS called relapsing-remitting MS (RRMS). With this type of MS, you may have mild, if any, symptoms on a daily basis but experience occasional relapses, which are attacks of symptom flare-ups. Once the attack has subsided, your symptoms may go away completely or return to a lower level. This is called remission. An attack is a sudden worsening of your old MS symptoms or the appearance of new symptoms. To be considered an attack, symptoms must last for at least 24 hours and occur at least 30 days after your last attack. Symptoms must not be related to an increase in your body temperature from heat exposure, fever, or exertion. In most cases, you can expect the attack symptom or symptoms to last several days to several weeks or longer. What Causes an MS Attack? MS is caused by a disordered immune system (your body's defense system), which mistakenly directs immune cells to attack the myelin, or protective lining around your nerves, of your central nervous system. Inflammation (swelling and irritation) from these attacks causes MS symptoms to flare. Experts can't say exactly why people with MS have attacks. For some, an attack may seem to be triggered by stress, but there is no hard evidence to back this up. How Do You Recognize an Attack? It can be hard to tell the difference between a true attack and a temporary flare-up of your day-to-day MS symptoms. You can have a worsening of symptoms that's not related to any new inflammation in your central nervous system. These symptoms are sometime called a pseudo attack and may be caused by overheating or infection. They are more likely to be symptoms you usually have, such as tingling, numbness or fatigue. Symptoms of an attack are different from person to person and may change from one attack to another, which can also make it complicated to tell whether you're having an attack or a flare-up. Here are some ways to help you recognize an attack: Old symptoms (one or more) are more severe, such as weakness or the loss of balance or vision. New symptoms (one or more) develop. Symptoms last longer than 24 hours. Symptoms cause loss of mobility. You lose the ability to function normally. Treating an Attack If you think you might be having an MS attack, let your MS healthcare provider know right away. Not all attack symptoms need to be treated. A worsening of symptoms like fatigue, confusion, balance or numbness may respond to rest at home. On the other hand, severe symptoms, such as a loss of vision or loss of mobility, are usually treated with high doses of corticosteroids. Corticosteroids are strong anti-inflammatory medications. Although they do not change the course of your disease, they usually help an MS attack go away more quickly. You may get steroids directly into your bloodstream by intravenous (IV) infusion for three to five days, or you may be given a pill to take. Many MS patients establish a contract with their MS doctor so that more expeditious therapy can be started if an MS attack occurs. This may include boosting current drug dosages or initiating some other emergency therapy. Having an MS attack is an expected part of having relapsing-remitting MS. Most attacks do not cause permanent damage, but the accumulation of attacks over time can. Medications called disease-modifying drugs are now available for relapsing-remitting MS, and these drugs have been shown to significantly cut down on the number of attacks. The best way to prevent an MS attack is to work closely with your medical team and get started on a disease-modifying drug as soon as possible after the diagnosis of MS is confirmed. Key Takeaways An MS attack is a flare-up of old or new symptoms that come and go unpredictably. Symptoms tend to be different from person to person and attack to attack. Attack symptoms usually start suddenly, are more severe than day-to-day symptoms, and last longer than 24 hours. High-dose steroids may help attack symptoms clear, but the only way to help prevent attacks is to take a disease-modifying drug. If you think you may be having attack symptoms, contact your care provider.