Types of Multiple Sclerosis

There are several types of multiple sclerosis varying primarily in the course of the disease throughout a patient's life. These differences in the natural history of the disease can be quite dramatic. It is unclear what determines which sub-type a given patient will have. Likewise, once a patient presents with early signs of multiple sclerosis it can be initially difficult (or impossible) to predict which progression they can expect in the future. It may only be once considerable time has passed, and the course of the disease and its related symptoms has been observed, that a given patient can be classified under one of the general types.

In a general sense, there are four sub types of multiple sclerosis, distinguished by the course the disease takes in that patient:

• Relapsing-remitting: This is the most common form of MS, particularly in the early course of the disease. Some patients who initially have relapsing-remitting MS later develop more progressive forms. It is characterized by periodic acute attacks or exacerbations of symptoms. These attacks can evolve over several days to weeks. Following the acute period, the symptoms can persist or can improve partially or fully. This recovery can take weeks to months. In between the acute attacks, the symptoms do no get worse.
• Primarily-progressive: Overall, this type is less common, only occurring in around 15% of patients, most commonly in people who present with the disease later in life (after around 40 years of age). It is characterized by a steady progression of symptoms and disability without the acute attacks and relapses that are seen in the more common relapsing-remitting type. These patients have a gradual worsening of central nervous system function and do no have periods of improvement.
• Secondary-progressive: In some patients who initially present with a relapsing-remitting form of MS, symptoms may become progressive, like in the primarily-progressive form described above, at some point in their life. These patients first have some period of relapsing-remitting MS, which can last anywhere from months to many years or decades. They then begin progressing without the acute attacks and remissions associated with that form.
• Progressive-relapsing: The least common form of MS, these patients have what amounts to be a superimposition of relapsing-remitting MS on top of primarily-progressive MS. They will experience gradual, steady progression of symptoms and disability but will also experience superimposed acute attacks where their symptoms get acutely worse and may or may not be followed by some improvement.