All four types of multiple sclerosis are caused by the immune system attacking the central nervous system, causing inflammation.

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Multiple sclerosis is a long-term (chronic disease) of the brain and spinal cord that usually starts in the early adult years and lasts for a lifetime. Unlike cancer or Alzheimer’s disease that have predictable progression and stages, MS has types of disease. These types describe how MS may progress. However, even within these types, the progression is different for different people. The type of MS someone has may change over time. Some people with MS have a mild form of the disease throughout their life and some have a course that gets progressively worse.

What Are the Four Stages of MS?

Most MS experts describe four types of MS, not stages. In all types of MS, the disease is caused by a person’s defense system – their immune system – attacking their central nervous system, which is the brain and spinal cord.

The attacks take the form of inflammation, which causes the symptoms of MS. In most cases, the symptoms go away between attacks of MS, called remissions. Over time, the attacks usually come back, called relapses. A relapse may leave permanent damage to nerve cells and the protective lining around nerve cells. This damage results in symptoms that remain between attacks:

• The most common type of MS is relapsing-remitting MS. Eighty-five to 90 percent of people start with this type of MS. In this type, attacks are followed by complete or almost complete remission of symptoms. People with this type do not have much progression of their disease. Common symptoms are fatigue, tingling and numbness, visual changes, and weakness.
• Secondary progressive type MS occurs in people who start with the relapsing-remitting type. Over time, people with this type have symptoms that remain between attacks and they have less relapses and remissions. The amount of progression, or disability, can range from mild to more severe.
• Primary progressive MS is less common than the other types, making up about 10 to 15 percent of cases. In this type, there are no remissions or relapses. People with this type have a gradual progression of their symptoms. The most common symptoms are heaviness and stiffness of the legs that make walking difficult.
• Clinically isolated syndrome is a type of MS that causes an attack similar to relapsing-remitting MS, but there may never be another attack. If symptoms of the attack cause central nervous system changes seen on an MRI brain imaging study, MS is likely to develop and a full diagnosis of MS can be made.
• Another type of MS recognized by some experts is called benign MS. It occurs in 5 to 10 percent of cases. In this type, MS remains mild and does not progress after 15 years.

MS Progression and Prognosis

The type of MS predicts the progression of the disease to some degree, but even within the types, there is a wide range of disability. Some factors that predict a more progressive course of MS are male sex (men are less likely to get MS but more likely to have severe MS), having primary progressive type, having more frequent relapses, having shorter periods of remission, and having more MRI changes.

Prognosis is the long-term prediction of the survival or disability of a disease. The prognosis for MS has improved with improved treatment. There are now many medication options that improve the prognosis and delay progression, called disease-modifying therapies. MS is not considered to be a fatal disease. With treatment, most people with MS live a close to normal lifespan, do not end up in a wheelchair, and will die of something other than MS.

To learn more about multiple sclerosis treatment and causes, read What is Multiple Sclerosis.