What is MS?

MS is believed to be an autoimmune disease in which the body’s immune system attacks its own tissues, causing inflammation in areas of the central nervous system (or CNS—made up of the brain, including the optic nerve and spinal cord). This inflammation causes damage to myelin, the fatty coating that protects nerve fibres (called axons). Damaged myelin may form scar tissue (sclerosis). Often, the nerve fibre itself may be affected. When any part of the myelin coating or nerve fibre is damaged, messages moving through the central nervous system can be disrupted. Damaged areas are often called lesions or plaques.

This can lead to a variety of symptoms, depending on where the damage occurs. For example, if the optic nerve is affected it may result in vision problems. If there’s damage to the sensory nerves, it may result in tingling, numbness, or pain.

A diagnosis of MS is based on a neurological examination, medical history, and other tools, such as magnetic resonance imaging (MRI), evoked potentials and a spinal tap. MS can sometimes take a while to diagnose or rule out.

The earliest form of MS is clinically isolated syndrome (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 (RRMS), the most common disease course at the time of diagnosis. 

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 or nearly complete to pre-relapse function, and this recovery persists for a clear period of time. A relapse generally indicates a worsening of inflammatory activity in the CNS. However, the frequency of relapses doesn’t indicate how active MS is: about 90% of MS lesions in the brain and spinal cord don’t result in any symptoms at all. However, during the periods when there are no MS symptoms, the disease is working under the radar, causing inflammation and damage to the nervous system.

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, sometimes with plateaus. Approximately half of the people with RRMS will develop SPMS within 10-20 years of diagnosis.

Primary-progressive MS (PPMS) is characterized by a slow accumulation of disability, without defined relapses. Approximately 10 per cent of people diagnosed with MS have PPMS.

Progressive-relapsing MS (PRMS) is the rarest course of MS, occurring in only about 5 per cent of people diagnosed. People with this form of MS experience relapses with steadily worsening disease from the beginning.

What is MS?