What is Multiple Sclerosis?
Multiple sclerosis (MS) is a disease of the central nervous system, which includes the brain, spinal cord, and the nerves that control vision. In MS, the body’s own immune system attacks the myelin sheath, the protective coating around nerve fibers, and sometimes the fibers themselves. This damage is called demyelination. The scars it leaves behind are called sclerosis, also known as lesions or plaques.
When myelin or a nerve fiber is damaged, the signals traveling to and from the brain slow down or get blocked. That is what causes MS symptoms. Early on, myelin can sometimes repair itself, and symptoms ease after an attack. Over time, though, the damage can become permanent. How MS affects you depends on its course, and there are a few main types.
Relapsing-Remitting MS
RRMS is the most common type. About 85 percent of people with MS start here. It has clear relapses, also called attacks or flares, followed by periods of recovery that may be partial or complete. Between relapses, the disease does not clearly get worse.
A relapse is a major worsening of old symptoms, or new symptoms, that lasts at least 24 hours and is not caused by infection, fever, or stress. It comes from a new area of inflammation and damage in the brain, spinal cord, or vision nerves. Most relapse symptoms improve with time, rest, and sometimes treatment, though some can linger. Without a disease modifying therapy, people with RRMS often have one to three relapses a year, though some go years between them.
Infection, fever, and stress can also cause a flare-up of old symptoms. This is called a pseudo-relapse, because there is no new damage. An MRI can help tell the two apart. A pseudo-relapse is treated by addressing the infection or stress behind it.
Primary Progressive MS
PPMS slowly gets worse from the start, without clear relapses. The pace can change, and there can be periods of stability. About 15 percent of people with MS begin with this type.
Secondary-Progressive MS
Some people who start with RRMS later move into SPMS. In this stage, disability slowly increases over years, with fewer or no relapses and fewer new spots on MRI. Not everyone with RRMS develops SPMS.
Clinically Isolated Syndrome
CIS is a first episode of symptoms that looks like an MS relapse in someone who has not been diagnosed with MS. People who have a CIS are at higher risk of developing MS, but not everyone does.
When to Talk to Your Provider
If you notice new symptoms, or old ones getting worse for more than a day, contact your MS care team. They can tell whether it is a true relapse or a pseudo-relapse and help you decide what to do next.
