Primary-progressive MS (PPMS) is characterized by steadily worsening neurologic function from the beginning. Although the rate of progression may vary over time – with occasional plateaus and temporary, minor improvements — there are no distinct relapses (also called attacks or exacerbations) or remissions.
PRMS is also characterized by steadily worsening neurologic function from the beginning, but with occasional relapses along the way. During these relapses, a person is likely to experience new symptoms or a sudden worsening of old symptoms, which last for awhile and then gradually subside.