Multiple sclerosis is classified according to frequency and severity of neurological symptoms, the ability of the central nervous system (CNS) to recover, and the accumulation of damage.
Primary progressive MS causes steady progression of symptoms with few periods of remission.
Relapsing-Remitting MS causes worsening of symptoms (exacerbations) that occur with increasing frequency, along with periods of reduced symptoms (remission).
Secondary progressive MS is initially similar to relapsing-remitting MS but eventually follows a progressive course without remissions.
Relapsing-Progressive MS causes cumulative damage during exacerbations and remissions.