About 20% of patients with relapsing-remitting MS experience little or no progression after a first attack for long periods of time, although by 25 years most patients have converted to a progressive phase.
Chronic-Progressive Multiple Sclerosis
The term chronic-progressive multiple sclerosis is used to describe cases in which symptoms continue to worsen slowly without remission. About 20% of multiple sclerosis patients (usually those whose first symptoms occur after age 45) have the chronic-progressive form without first developing relapsing-remitting MS. Chronic-progressive MS generally follows a downhill course, but its severity varies widely. Three variants are commonly used to define this patient group:
- Secondary-Progressive MS (SPMS). SPMS is the natural evolution of relapsing-remitting MS and develops in about half of patients during the first 10 years and nearly all of them within 25 years. It follows a progressive course of nerve and muscle deterioration with occasional acute flare-ups, remissions, and plateaus.
- Primary-Progressive MS (PPMS). PPMS progresses continuously and gradually from the first onset of symptoms and has no remissions. It occasionally levels off, and minor improvement is even possible. This occurs in about 10% of patients, who tend to be older than average at the time of diagnosis.
- Progressive-Relapsing MS (PRMS). PRMS is progressive from the start with acute symptom flare-ups, but may have some relapses with continued deterioration between them. It occurs in less than 5% of patients.
Because the natural courses of primary-progressive and progressive-relapsing MS are similar, some experts believe this distinction is unnecessary.
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