Multiple sclerosis is a neurodegenerative disorder that is based on demyelination, or damage to the myelin sheaths that protect the nerve fibers (axons) of the central nervous system. The central nervous system consists of the brain, spinal cord, and optic nerves.
With multiple sclerosis, myelin is damaged in multiple areas, which leaves scar tissue known as scleroses. Sometimes the axon itself is damaged or broken. The ability of the nerves to send messages to and from the brain is disrupted, producing the symptoms of multiple sclerosis.
The symptoms of this disease tend to occur episodically and usually appear in acute periods of worsening with a gradually progressive deterioration of neurologic function. Multiple sclerosis relapses are often unpredictable, occurring without warning or obvious triggering factors.