What type of MS do I have?
December 23, 2014
Traditionally, MS has been divided into four clinical courses: relapsing/remitting, primary progressive, secondary progressive and progressive relapsing. These four were intended as descriptions of the different courses that MS could take in patients, and were not based on any particular understanding of the biology of the disease, the cause of the disease, or even the prognosis of patients with the different types of MS. Over the years, our understanding of MS has improved, and these descriptions of the disease course no longer meet our needs to describe the disease.
Over the past couple of years, there has been a revision of our classification of MS, resulting in a publication in July 2014. The recommendations of this revision have been increasingly adopted by MS experts. The new revisions retain three of the MS courses: relapsing/remitting, primary progressive, secondary progressive. Relapsing/remitting disease includes patients with attacks of MS, where new neurology symptoms develop over the course of a few days. Patients may or may not fully recover from these attacks, but they do not worsen further unless another attack occurs. Primary progressive MS slowly worsens over time, usually over many months. These patients never have attacks where they suddenly worsen over a few days. Secondary progressive MS begins with a relapsing/remitting course, but after a few years changes so that the baseline slowly worsens over months similar to the primary progressive course. They may or may not continue to have attacks on top of the underlying slow worsening of symptoms.
The new classification also recognizes that these three courses of MS are not adequate to fully describe the disease. Instead, we are now encouraged to attach two additional modifiers: an assessment of disease activity and disease progression. The assessment of disease activity is an indication of whether patients are continuing to have attacks of MS. Attacks are an indication that the immune system is actively causing damage to the nervous system. It is important to know the timeframe over which attacks occur, so a typical disease activity modifier would state that a patient had “active disease with 2 attacks over 18 months”. If patients had no attacks it could be stated that the MS was “inactive over 18 months”, meaning that there were no attacks of MS over the past 18 months.
The modifier for disease progression is an indication of whether patients are accumulating disability over time. This is meant to indicate worsening that occurs in the absence of MS attacks, so it is important to note which patients worsen due to a slow worsening of the disease over months (primary and secondary progressive disease) and those that worsen because of incomplete recovery from attacks (relapsing/remitting disease). The term “worsening” is used to describe people with relapsing/remitting MS who are having increased disability because of incomplete recovery from attacks. The term “progression” is used to describe people with primary or secondary progressive MS who are having increased disability because of a slow worsening of their symptoms over months.
People with relapsing/remitting MS who are completely stable would be classified as inactive and not worsening. Those with attacks would be classified as active. These active cases could be further classified as active with worsening or active without worsening depending on whether they had increasing symptoms after the attack subsided.
People with secondary progressive MS who are stable could be classified as inactive and not progressing. Those with attacks would be active, and either progressing or not progressing depending on whether they were developing more disability over months. Those without attacks would be inactive and either progressing or not progressing depending on whether they were developing more disability over months.
People with primary progressive MS would usually be classified as inactive because they do not have attacks. However, some people start with a primary progressive course of disease and later have an occasional MS attack, and these would be classified as active. These types of primary progressive MS would be further classified as progressing or not progressing depending on whether they were developing more disability.
It is important to remember that these types of MS are intended to allow us to better describe the course that MS takes in different people. The type of MS does not imply any difference in the speed with which people get more disability and it does not indicate prognosis. Better classifications should allow us to better describe the course of MS in populations and how different people are affected by the disease.