To describe the natural history of a condition or disease. To describe the natural history of a condition or disease. To determine effectiveness or cost effectiveness of treatments/services and/or health care products. To measure or monitor safety and harm. To measure quality of care.
According to the NMSS, attacks or flare-ups of symptoms only qualify as exacerbations if: 1  they occur at least 30 days from an earlier flare-up. 2  symptoms last for 24 hours or longer.
This is what leads to the symptoms of MS. Damage to the myelin sheath is believed to cause ârelapsesâ, or MS attacks. In these attacks, symptoms flare up and last for anything from 24 hours to several months.