Multiple sclerosis is an autoimmune disorder of the central nervous system (brain and spinal cord), which is characterised by decreased nerve function due to myelin loss and secondary axonal damage.
Symptoms of multiple sclerosis (MS) develop as a result of multiple lesions in the brain and spinal cord and the gradual destruction of myelin, a fatty substance that covers the nerve fibers. The patient's symptoms vary depending on the areas of the brain or spinal cord affected. It is diagnosed most frequently between 20 to 40 years of age and is one of the major causes of disability in adults.
Patients may present with a wide variety of symptoms, such as loss of vision, double vision, nystagmus, difficulty with speech, tremors, unsteady gait or numbness. Various cognitive impairments are also common, such as difficulty performing multiple tasks at once, difficulty following detailed instructions, and loss of short term memory. (A diagnosis of MS requires two distinct neurological episodes--that is, two different symptoms, or the same symptom vanishing and recurring.)
The reasons for disability are not only the neurologic symptoms but also various complications such as muscle spasticity, fatigue, urinary incontinence, and depression.
The symptoms can vary in intensity from time to time. An acute flare-up of the symptoms, either an increase in intensity or a new symptom, is referred to as an exacerbation. The disease is often categorized based on the frequency and consistency of the symptoms as either relapsing remitting or chronic progressive. In relapsing remitting MS, patients may experience an exacerbation that may go away by itself after a period of time, and symptoms may stay relapsed indefinitely or return at random. In chronic progressive, the symptoms continue to increase without relapse. These descriptions are based on symptoms and not on the underlying disease mechanisms. Recent Magnetic Resonance Imaging studies show that nerve damage continues in relapsing remitting patients even if symptoms subside. In either case, a great majority of diagnosed patients end up with permanent disability due to accumulating myelin loss and axonal damage. (One Canadian study, autopsying several thousand people who had died from all causes, found that less than half of the people with brain lesions and loss of myelin had been diagnosed with MS; most of the undiagnosed cases involved people with few if any symptoms, rather than the difficulty in diagnosing MS.)
Exacerbations can occur at any time, but some outside sources can definitely influence their recurrence. Physical or emotional stress are common causes. Heat is also a common problem, and many patients must avoid intense exercise, saunas, or even hot showers.
Myelin destruction is now known to occur due to an autoimmune attack (a kind of inflammation resulting from antibodies or lymphocytes that the body produces against its own tissues). The exact cause of this inflammation is not known. Current studies suggest that there is a combination of genetic predisposition plus an outside agent, perhaps a virus, that causes a person to contract the disease. Thus, MS patients are asked not to donate blood.
There is no known definite cure for multiple sclerosis. Treatment is aimed maintaining the maximum quality of life. There are three primary forms of medication used to treat the symptoms:
- During an exacerbation, corticosteroids (such as prednisone) or azathioprine (experimental) are used to reduce inflammation, relieving stress on the damaged nerves and myelin. While, corticosteroids are more beneficial for acute attacks, azathioprine is expected to be effective within a long period of time.
- Longer-term treatment using interferon beta-1a or 1b (Avonex, Betaseron, Rebif) or glatiramer acetate (Copaxone) is intended to regulate the autoimmune attacks. As of 2001, interferon beta is the only medication shown to actually slow the progression of the myelin damage in a significant number of patients.
- A variety of medications, many originally developed for other purposes, are used to treat chronic symptoms. For example, the anti-seizure drug Neurontin, as well as anti-spasmatics, such as baclofen and Zanaflex, are useful against spasticity; SSRIs are used for depression; and a variety of stimulants are used to treat fatigue.
Studies investigating any relationship between MS and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP), with/to Hepatitis C (HCV), are continuing.