Multiple sclerosis (MS) is expressed differently in each individual. In 2013 an international committee defined four main types of the disease:
- Clinically isolated syndrome (CIS) is the first onset of neurological symptoms in the central nervous system that is caused by inflammation and myelin damage. This event, which by definition must last at least 24 hours, does not yet meet the criteria for MS, as people who experience the syndrome will not necessarily develop MS.
People with CIS may be treated with ”disease-modifying drugs” (DMTs) because it has been shown that early treatment may delay the onset of multiple sclerosis.
- Relapsing-Remitting MS (RRMS) -this is the most common MS type. About 85% of people living with MS are initially diagnosed with RRMS. This form of the disease is characterized by flare-ups of neurological symptoms (also called recurrences or attacks) accompanied by periods (weeks, months, or years) of partial or complete recovery (remission). During remission, all symptoms may disappear, or some of the symptoms may persist and remain constant. The affected nerves, the severity of the attacks, the degree of recovery, and the duration between seizures, vary significantly from person to person.
- Secondary Progressive MS (SPMS) – Some people who are diagnosed with RRMS will progress at some point (between 10 and 20 years after the initial diagnosis) to advanced secondary MS. This form of the disease is characterized by the fact that the symptoms are steadily worsening over time. The disability increases with or without evidence of the disease activity. Attacks may occur from time to time, as well as the periods of stability. Here, too, the symptoms get worse at a different rate for each person.
- Primary progressive MS (PPMS) – This type of MS is not very common. It occurs in about 10% of those patients diagnosed with multiple sclerosis. This form is characterized by a slow worsening of symptoms and deterioration of neurological function from the start, without recurrence or remission. The disease gradually gets worse over time. Some doctors define another type of MS: Progressive-Relapsing MS (PRMS), which is a rare form of multiple sclerosis. The characteristics are similar to the symptoms of PPMS. However, this form of the disease occurs with seizures.