Each person's MS journey is unique; however, distinct patterns are seen over time.
In 1996, the National MS Society introduced categories of MS which defined these common patterns.
Definition of the categories came as the result of an international survey conducted among scientists who specialize in MS research and patient care.
Approximately 10% of people are diagnosed with Primary-Progressive MS which is characterized by slowly worsening neurological function from onset.
The steady accumulation of disability may reach occasional plateaus and temporary minor improvements, but there are no distinct relapses or remission.
Primary-Progressive MS generally appears in people in their forties and affects men and women equally.
In a relatively rare version of the disease, approximately 5% of people are diagnosed with Progressive-Relapsing MS which is also characterized by steady worsening of disease from the beginning.
However, in Progressive-Relapsing MS, there are clear exacerbations of deficient neurological function from which the person may or may not experience some recovery, but without true remissions.
About 85% of people are initially diagnosed with Relapsing-Remitting MS which is characterized by unpredictable, but clearly defined, attacks of deficient neurological function.
During these attacks (relapses, exacerbations, flare-ups), new symptoms appear or existing symptoms become more severe, after which there may be partial or complete recovery (remission).
Benign MS is a subset of RRMS which is characterized by very mild and infrequent relapses.
Recovery from attacks is complete without accumulated worsening of neurological function.
Approximately 15-20% of people with MS have this form of the disease. Benign MS can only be identified when there is minimal disability 10-15 years after onset and tends to be associated with less severe symptoms at onset (e.g. sensory or sight).
While 25% of people remain Relapsing-Remitting MS, approximately 40% of people with MS go on to develop Secondary-Progressive MS in which the disease worsens more steadily, with or without occasional flare-ups, minor recoveries, or plateaus.
When attacks do occur, the recovery is usually not complete, so permanent disability accumulates.
Long-term data is not yet available to determine the extent which early treatment with disease-modifying drugs (DMD) may significantly delay or limit this transition.
Before DMDs became available, approximately 50% of people with RRMS developed Secondary-Progressive MS within 10 years.
However, it should be encouraging that the ongoing research into halting the process of MS will someday prevent accumulated disability and neurological dysfunction.
Keep in mind that life expectancy for persons with MS is near normal and that approximately 45% of people living with MS are not severely affected and live normal and productive lives.
Multiple Sclerosis International Federation - About MS - Types and Course
National Multiple Sclerosis Society - What is Multiple Sclerosis?
Defining the Clinical Course of Multiple Sclerosis - Neurology 1996;46:907-911
Multiple Sclerosis: Current Status and Strategies for the Future (2001)