In some ways, each person with multiple sclerosis lives with a different illness. Although nerve damage is always involved, the pattern is unique for each individual with MS.
Specific experiences with MS may vary widely, but doctors and researchers have identified several major types of MS. The categories are important because they help predict disease severity and response to treatment.
In primary progressive multiple sclerosis, symptoms continually worsen from the time of diagnosis. There are no well-defined attacks, and there is little or no recovery. Between 10% and 15% of people with MS have primary progressive MS.
Several aspects of primary progressive MS distinguish it from other types of MS:
People with primary progressive MS are usually older at the time of diagnosis -- an average age of 40.
Roughly equal numbers of men and women develop primary progressive MS. In other types of MS, women outnumber men three to one.
Primary progressive MS usually leads to disability earlier than relapsing-remitting MS (see below).
Perhaps the most upsetting difference in primary progressive MS is its poor response to treatment. So far, no treatments have been shown to help, although studies are ongoing.
Relapsing-Remitting Multiple Sclerosis
Most people with multiple sclerosis -- around 90% -- have the relapsing-remitting type. Most people with this type of MS first experience symptoms in their early 20s. After that, there are periodic attacks (relapses), followed by partial or complete recovery (remissions).
The pattern of nerves affected, severity of attacks, degree of recovery, and time between relapses all vary widely from person to person.
Eventually, most people with relapsing-remitting MS will enter a secondary progressive phase of MS.
Secondary Progressive Multiple Sclerosis
After living with relapsing-remitting MS for many years, most people will develop secondary progressive MS. In this type of MS, symptoms begin a steady march, without relapses or remissions. (In this way, secondary progressive MS is like primary progressive MS.) The transition typically occurs between 10 and 20 years after the diagnosis of relapsing-remitting MS.
It's unclear why the disease makes the transformation from relapsing-remitting to secondary progressive MS. A few things are known about the process:
The older a person is at original diagnosis, the shorter the time for the disease to become secondary progressive.
People with incomplete recovery from initial relapses generally convert to secondary progressive MS sooner than those who recover completely.
The process of ongoing nerve damage changes. After the transformation, there's less inflammation, and more slow degeneration of nerves.
Secondary progressive MS is challenging to treat -- and to live with. Treatments are moderately effective at best. Progression occurs at a different rate in each person and generally leads to some disability.