The course of MS is unpredictable. Some people may feel and seem healthy for many years following diagnosis, while others may be severely debilitated very quickly. Most people fit somewhere between these two extremes.
Although every individual will experience a different combination of MS symptoms, there are a number of distinct patterns relating to the course of the disease:
In this form of MS there are unpredictable exacerbations or attacks (called relapses) during which new symptoms appear or existing symptoms become more severe. Relapses can last for varying periods (days or months) and there is partial or total recovery (remission). The disease may then be inactive for months or years.
About 85 per cent of people with MS are initially diagnosed with relapsing-remitting MS.
Primary progressive MS
About 10 per cent of people with MS are diagnosed with this form of MS, which is characterised by a lack of distinct attacks, but with slow onset and steadily worsening symptoms. There is a build-up of disability which may level off at some point or continue over months and years.
Secondary progressive MS
For most people who initially have relapsing-remitting MS, there is the development of progressive disability later in the course of the disease. This often occurs with superimposed relapses and no definite periods of remission.
Progressive relapsing MS
This is the least common subtype (about 5 per cent). Individuals show a steady neurologic decline with a clear superimposition of attacks. There may or may not be some form of recovery following these relapses, but the disease continues to progress without remissions.
Some people live with MS for many years without accumulating disability.This group has so-called benign MS. It is the mildest form of MS that is clinically apparent. People with benign MS have a minimal amount of physical disability after ten years or more of the disease. Early identification of benign MS is important in deciding who should or should not take lifelong disease-modifying treatments.
Benign MS cannot be diagnosed at the onset of the disease but only becomes clear over time. Moreover, long-term follow-up has found that many people with benign MS do go on to develop progressive disease, and therefore labelling someone as having benign MS too early in the disease course may be misleading.
Though MS is rare in children, an increasing number of children across the world are being diagnosed with MS. Neurologists are finding that MS in children has different characteristics and to date, no therapies have been tested for being safe or effective for the treatment of children with MS.
The International Paediatric MS Study Group is helping to improve this knowledge.
Course of MS
It is impossible to predict the course of MS accurately for any individual, but the first five years give some indication of how the disease will continue for that person. This is based upon the course of the disease over that period and the disease type (relapsing-remitting or progressive). The level of disability reached at endpoints such as five and ten years is thought to be a reliable predictor of the future course of the disease.
Age at onset and gender may also be indicators of the long-term course of the disease. Some research has indicated that younger age at onset (under 16 years of age) implies a more favourable prognosis, but this must be tempered by the knowledge that, for a young adult, living with MS for 20 or 30 years may result in substantial disability even if the progress towards disability is slow.
Other research has indicated that late onset (over 55 years of age), particularly in males, may indicate a progressive course of the disease.