The course of multiple sclerosis varies for each person. Because of this uncertainty, doctors often tell their patients that they "probably" or "possibly" have MS. Your diagnosis is based on the combination of problems, patterns of recurrence, which systems are impaired and your test results. There is no way to predict how each person's condition will progress. It often takes years before a doctor can be certain of an MS diagnosis and have some idea on how the disease will progress.
There are four courses that MS takes:
Relapsing-remitting MS: characterized by unpredictable acute attacks, called "exacerbations," with worsening of symptoms followed by full, partial or no recovery of some function. These attacks appear to evolve over several days to weeks. Recovery from an attack takes weeks sometimes months. The disease does not worsen in the periods between the attacks. This pattern usually occurs early in the course of MS in most people.
Primary-progressive MS: characterized by a gradual but steady progression of disability, without any obvious relapses and remissions. This form of disease occurs in just 15% of all people with MS, but it is the most common type of MS in people who develop the disease after the age of 40.
Secondary-progressive MS: initially begins with a relapsing-remitting course, but later evolves into progressive disease. The progressive part of the disease may begin shortly after the onset of MS, or it may occur years or decades later.
Progressive-relapsing MS: This is the least common form of the disease and is characterized by a steady progression in disability with acute attacks that may or may not be followed by some recovery. People with progressive relapsing MS initially appear to have primary progressive MS.
Most people with MS are diagnosed between the ages of 20 and 40, but the unpredictable physical and emotional effects of the disease continue throughout the person's life.
What Is a True Exacerbation (Relapse)?
A true exacerbation of MS is caused by an area of inflammation (swelling) in the nerves of the brain and spinal cord system followed by something called demyelination, which is the destruction of myelin. The myelin is the fatty sheath that surrounds and protects the nerve fibers.
Demyelination results in the formation of an abnormal area called a plaque within the brain and/or spinal cord. A plaque causes the nerve impulses to be slowed, distorted, or halted, producing the symptoms of MS. One example of an exacerbation of MS would be the development of optic neuritis, an inflammation of the optic nerve (which is in the back of the eye) that impairs vision.
An exacerbation of MS may be mild and not cause a noticeable impairment in functioning or may significantly interfere with a person's daily life. Exacerbations usually last from several days to several weeks, although they may extend into months.
Exacerbations or relapses of MS are often treated with medications called corticosteroids. These drugs reduce inflammation. It is generally accepted that taking corticosteroids for a short amount of time will shorten an exacerbation and/or reduce the severity.
What Is a Pseudoexacerbation?
Sometimes an increase in symptoms has nothing to do with the underlying MS, but is caused by factors such as fever, infection or hot weather that can temporarily aggravate MS. This is referred to as a pseudoexacerbation. For example, some people report a worsening of their symptoms during or after periods of intense stress.
What Is Remission?
A remission does not mean that all the symptoms of MS disappear, but rather that a person with MS mostly returns to the way they were before the last exacerbation or relapse began.