Currently, MS is classified into three groups based on the clinical and radiological activity of the disease and its potential progression:
This type affects around 85% of people with MS. In fact, it is the most common initial form of the disease.
Individuals in this group will experience unpredictable relapses where symptoms can appear at any time (both new and familiar). Symptoms can last from days to weeks and then disappear. At other times, the patient may not present symptoms; however, inflammatory lesions in the central nervous system may be occurring, which is known as subclinical disease activity.
In this type of MS, there is no observed increase in disability progression during periods between relapses.
It is less common than the relapsing-remitting form. In fact, initially, it affects only 10% of all patients with this disease. Flare-ups may or may not occur, but they are less frequent than in the previous type. It is characterized by a continuous or gradual progression of disability from the onset.
Finally, Secondary Progressive Multiple Sclerosis (SPMS) arises when between flare-ups, the degree of disability persists and/or worsens. Patients reach this advanced type of MS after a relapsing-remitting phase. Approximately 30-50% of patients who start with the relapsing-remitting form of MS typically develop secondary progressive MS with or without flare-ups.
Source: Book "Most Frequent Questions about Multiple Sclerosis" carried out with the support and collaboration of Dr. Ángel Pérez Sempere.