Multiple Sclerosis (MS) is a chronic central nervous system (CNS) disease which affects the brain, spinal cord, and optic nerves. Even in the absence of symptoms, the disease is continuously active (causing brain damage) from early stages of MS.
In recent times, MS prevalence rates in India have been revised from 1 case in every lakh to 3 cases/100,000 people – compare this to US, where MS occurs in 1 per 1000 people. MS is an autoimmune disease because the MS patient’s immune system (body’s defence against infection) attacks a part of its own body – the nerve cell myelin sheath. The nervous system consists of billions of neurons (nerve cells) which relay messages within the brain and between the brain and other body parts. In a normal nervous system, nerves (bundles of nerve cells) pass messages amongst themselves at superfast speed. The axon (long arm of a nerve cell) is covered by the myelin sheath (multi-layered bands) with small gaps in between. The nerve impulses, that is, chemical signals jump from gap-to-gap and rapidly spread the messages to surrounding nerve cells.
MS is neurodegenerative because the damaged myelin sheath and oligodendrocytes (cells that produce myelin) delay communication between nerve cells resulting in inefficient functioning of various body systems. Demyelinating (without myelin sheath) nerve cells occurs in multiple areas of the brain and nervous system. Damaged portions of the axon undergo sclerosis (develop hardened scars). A noteworthy feature of MS is the remissions (remyelination with improved symptoms) and relapses (further demyelination with worsened symptoms) cycle that occur over time.