There are various types of MS:
- Clinically Isolated Syndrome
- Relapsing-remitting MS
- Secondary-progressive MS
- Primary-progressive MS
The earliest form of MS is clinically isolated syndrome, or CIS. CIS refers to a single episode of neurological symptoms suggestive of multiple sclerosis. Often, on investigation using MRI the doctor finds evidence of another abnormality in the brain or spinal cord. Having multiple attacks of symptoms defines relapsing-remitting MS, the most common disease course at the time of diagnosis.
Relapsing-remitting MS (RRMS) is characterized by unpredictable but clearly defined relapses (also known as attacks, exacerbations or flare-ups) during which new symptoms appear or existing ones get worse. In the period between relapses, recovery is complete (figure 1a) or nearly complete (figure 1b) to pre-relapse function (remission).
Secondary-progressive MS (SPMS) follows a diagnosis of RRMS. Over time, distinct relapses and remissions become less apparent and the disease begins to progress steadily (figure 2a), sometimes with plateaus. About half of people with relapsing-remitting MS start to worsen within 10-20 years of diagnosis, often with increasing levels of disability (figure 2b).
Primary-progressive MS (PPMS) is characterized by a slow accumulation of disability, without defined relapses (figure 3a). It may stabilize for periods of time, and even offer minor temporary improvement (figure 3b) but overall, there are no periods of remission. Approximately 15 per cent of people diagnosed with MS have PPMS. About five per cent of people diagnosed with PPMS experience occasional relapses with steadily worsening disease from the beginning.