Damage to your nerves

Multiple Sclerosis is a disease of the central nervous system (CNS); it damages the protective coating around the nerve fibres (Figure 1.1) which transmit messages to all parts of your body, especially those controlling muscular and sensory activity. It is thought to be an ‘autoimmune disease’: this is where your body’s own immune system appears to attack itself. As the damage to the protective coating around the nerve fibres – called
‘myelin’ – increases, it leads to a process known as ‘demyelination’ (Figure 1.2), where the coating is gradually destroyed. These nerves then become less and less efficient at transmitting messages. The messages, as it were, ‘leak’ from the nerve fibres where demyelination has occurred, rather like the loss of an electric current through a cable that is not insulated. As the messages ‘leak’, they become weaker and more erratic, thus leading to greater and greater difficulty in controlling muscles or certain sensory activities in various parts of your body.

Healthy nerves

Damages nerves

Problems of repair

Which nerve fibres are demyelinated, in which order, and at what rate, varies very widely between individuals, so the corresponding loss of muscular and sensory control also varies widely. Moreover, even when damage does occur to the myelin, it is sometimes gradually repaired (i.e. some remyelination occurs) through internal body repair mechanisms; also, what might be described as ‘inflammation’ at the site of the damage often becomes less over time. However, in Multiple Sclerosis the rate of repair is slower than the rate at which the myelin is damaged; so the damage tends to accumulate more and more throughout the CNS. This damage results in plaques or lesions, which take the form of patchy scarring (areas of multiple ‘sclerosis’) where the demyelination has occurred. Thus the name ‘multiple sclerosis’ has evolved.