To find out more about progression of the disease

Multiple sclerosis (MS) is a chronic inflammatory disease affecting the central nervous system, causing the immune system to destroy the sheath of the nerve fibers (myelin) of the brain, spinal cord and the optical nerves.

MS can be characterized by two different events:

  • Relapse (or attack): the appearance, generally over a few hours or days, of neurological symptoms (difficulties with walking and balance, tingling and numbness, vision problems, etc.) lasting between a few days and a few weeks (but always longer than 24 hours), then suddenly disappearing, either completely or leaving certain after-effects.
  • Progression: the slow, insidious appearance of neurological disorders similar to those described for the relapses but over a period of at least six months, with no regression.

Depending on the occurrence of these two events during a patient's life, disease courses are defined:

  • Clinically isolated syndrome (CIS): patients who have had just one attack;
  • Relapsing-remitting MS: the patients suffer relapses with partial or full recovery, and symptoms are stable between two relapses;
  • Secondary progressive MS: after a phase of relapsing-remitting MS, symptoms start to get progressively worse;
  • Primary progressive MS: the symptoms gradually worsen from the start.

Description de l’évolution de la maladie

MS epidemiology


MS starts at the age of 30 on average, i.e. a time in life when people are in the middle of building their personal, family, professional and social lives. The cause of the disease is not yet known and it is likely that a combination of several factors leads to onset of the disease, including genetic, environmental and infectious factors.

icone_sep2Women are three times more affected than men.


In France, MS strikes 1 in 650 people, i.e. between 80,000 and 120,000 people, with 5,000 new cases being diagnosed each year.

icone_sep4MS has little impact on life expectancy. However, historically, it could cause serious disability, heavily altering the lives of those affected. On average, it caused definitive walking difficulties after 10 years, the need for a cane after 20 years and the use of wheelchair after 30 years. The recent developments of high-effective therapies allow to reduce the frequency of relapses and significantly delay the disability onset. A much better long-term prognosis can be anticipated amongst recently diagnosed and early-treated patients. However, no treatment has yet been found to cure MS or improve its effects.