THE brain and spinal cord comprise nerves that communicate with the rest of the body and each other through electrical impulses.
Each nerve fibre is surrounded by a protective sheath containing a substance called myelin, which works like the insulation around an electrical wire. The presence of myelin is necessary for electrical impulses to travel along the nerves in a proper manner.
Sometimes, small patches of inflammation affect parts of the myelin sheath and the nerve. When this happens, the affected nerve cannot function properly. After the inflammation clears up, the nerve functions normally again.
Repair of the myelin occurs only in the early stages of the condition. With each episode of inflammation, scars (sclerosis) may form on the nerve. Over a period of time, the nerve becomes permanently damaged.
A person who suffers from multiple sclerosis (MS) has multiple areas of scarring of the nerves in the brain and spinal cord. The exact cause of MS is unknown. It is thought to be an auto-immune condition.
The body's immune system protects us from external agents like bacteria and viruses by attacking them. It is thought that in MS, parts of the immune system, called T cells, attack the myelin sheaths of the nerves of the brain and spinal cord.
Some agents in the external environment, like a virus, may set off the immune system attack in people with a certain genetic make-up. Though it is not inherited, close family members of a person with MS have an increased risk of getting the condition.
MS is the most common disabling neurological disorder affecting young people with about 1 in 1,000 Britons suffering from the condition. It usually affects people aged between 20 and 40, and is twice as common in women compared to men. Once a person gets MS, it does not go away and the sufferer has to live with it for the rest of his or her life.
Each affected person has a different set of symptoms, which may differ in subsequent attacks.
The primary symptoms are reflective of the nerves that are affected. They include muscle weakness or spasms, numbness, tingling sensation, bladder, bowel and/or sexual dysfunction, visual disturbances, speech and/or swallowing difficulties, cognitive problems, e.g. problems with memory, concentration, reasoning and/or judgment, mood swings, emotional outbursts, loss of balance, dizziness and fatigue.
The secondary symptoms appear later in the condition, e.g. urinary tract infection, osteoporosis, muscle atrophy and skin breakdown. This may result in loss of income and mobility, social isolation and depression.
Types of MS
The classification of the different types of MS is controversial. Although used commonly, its epidemiological basis is not strong and there are no studies of its reliability.
There are clearly defined relapses with full recovery or residual deficit upon recovery. The symptoms are unpredictable and may last for varying periods of time, ranging from days to months. The periods between the relapses are characterised by an absence of disease progression. About 80%-85% of MS sufferers have this type at the outset.
The initial relapses and remissions are followed by progression with or without occasional relapses, minor remissions and plateaux. The disability does not go away after relapse and progressively worsens between attacks. About 65% of those with the relapsing remitting type develop the secondary progressive type within 15 years of the onset of the condition.
The condition progresses slowly from the outset without relapses or remissions. The problems tend to occur in one area and are often related to walking. About 10%-15% of MS sufferers have this type.
This starts with mild attacks and is followed by complete recovery. Such a diagnosis can only be made if there has been little or no disability for 10 to 15 years.
This has a rapid course leading to severe disability or death within five years. This type of MS is very rare.
The symptoms of MS are variable and may be transitory at the initial stages, so sufferers may delay seeking medical attention. This is compounded by the fact that there is no specific diagnostic test for the condition. The diagnosis is usually made on the following basis viz:
A history that is indicative of the condition.
Neurological examination findings that are consistent with the condition.
Positive evidence from magnetic resonance imaging (MRI) and nerve studies.
Sometimes a lumbar puncture may be needed.
The diagnosis is usually made by a neurologist based on evidence from the history and physical examination, that there are abnormalities in the central nervous system. The myelin sheath that is lost in MS is replaced by water that can be seen on the MRI scan. Some people may feel claustrophobic when the MRI is done. Others may find the loud noises uncomfortable.
MRI scans are abnormal in more than 90% of MS sufferers. As such, it is always considered together with the history and findings of physical examination.
The use of MRI has made available objective evidence of spread of the condition, sometimes even before another relapse occurs. Earlier diagnosis has facilitated the prescription of medicines that modify the condition, thereby impacting on subsequent disability.
Nerve conduction studies are sometimes used in the diagnosis of MS. Lumbar punctures are done when the diagnosis is uncertain. A white blood cell count of more than 5-35 per cubic millimetre is indicative of MS.
In summary, the diagnosis of MS is complicated by the fact that there is no specific diagnostic test.
(Written by Dr Milton Lum)