Three major subtypes:

• Relapsing-remitting MS (RRMS) is characterized by recurrent attacks of neurologic dysfunction over days to weeks with or without recovery; between attacks, no progression of neurologic impairment is noted. Accounts for 85% of new-onset MS cases.
• Secondary progressive MS (SPMS) always initially presents as RRMS but evolves in many pts into SPMS (~1-2% each year).
• Primary progressive MS (PPMS) is characterized by gradual progression of disability from onset without discrete attacks; 15% of new-onset MS cases.

Historically, 15 years after diagnosis only 20% of pts have no functional limitation and one-third to one-half have progressed to SPMS and require assistance with ambulation. With the introduction of disease modifying therapies for MS, the long-term course of the disease may have become less disabling.