A Tour around Multiple Sclerosis

(Date of publication 20th October 2005)

Here's a nugget of information for trivia addicts – St Lidwina of Schiedam, a Dutch nun who is the patron saint of skaters, was possibly the first recorded case of multiple sclerosis (MS). Apparently, she fell while skating and subsequently developed walking difficulties, headaches and violent pains in her teeth, her condition gradually deteriorating thereafter.

Understanding MS requires a knowledge of the structure of nerve cells, or neurones. Essentially, these cells have two types of processes: dendrites which receive impulses, and axons (usually only one per cell) which transmit impulses to other cells. Many axons are covered by a lipid-rich myelin sheath which is discontinuous at intervals termed the Nodes of Ranvier, and these nodes play a vital role in the propagation of electrical signals. Here is a cross-section of the myelin, showing its lamellar structure. In MS the myelin sheath of cells in the central nervous system (CNS) becomes damaged or destroyed, as in this diagram, interfering with impulse transmission.

A simple outline of MS, an autoimmune condition, is provided by the Journal of the American Medical Association. Affected areas of the brain and spinal cord appear as distinct lesions when subjected to magnetic resonance imaging (MRI) – the bright areas on these scans of patients in early stage and late stage MS indicate active disease. Symptoms include visual disturbances, difficulty in walking, loss of sensation and fatigue or weakness. The most common presenting symptom is optic neuritis (ON), an inflammation of the optic nerve, which is highly variable and can produce anything from a slight loss of visual acuity to blindness. On this site a sufferer describes his own experience of ON. In 70% of cases only one eye is affected.

An alternative source of basic information about MS is the interactive tutorial provided by the US National Library of Medicine. (Does the same deep-voiced American male do every voiceover?) The course of the disease is unpredictable, but there are four distinct patterns or phenotypes (some authorities feel that the term 'Benign MS' should no longer be used). In Relapsing/Remitting MS, there are unpredictable exacerbations when symptoms appear or become more severe, interspersed with periods of partial or total remission. These patients may subsequently develop Secondary Progressive MS, characterised by progressive disability, during the later stages of the disease. In Primary Progressive MS there are no distinct relapses but a slow onset and a steady worsening of symptoms. Relapsing Progressive MS is the least common type and has a similar gradual increase in disability from the start, but this is accompanied by one or more exacerbations.

The emedicine site has a recent article with comprehensive clinical information. No aetiological agent has been identified and genetic susceptibility may be a factor, as the condition is more common in Caucasian populations living in northern latitudes (see this map of the world-wide occurrence, in which darker areas indicate a higher incidence). Some specialists believe that the disorder could be triggered by several different environmental agents, as a result of molecular or epitopic mimicry. The theory is that the chemical signature used by the immune system to recognise a specific foreign invader, such as a virus or bacterium, also occurs in the body’s own tissues. As well as attacking the invader, the immune system therefore mistakenly attacks the body, giving rise to autoimmune phenomena. However, only 1 in 4 MS attacks is associated with a viral infection.

Patients with MS have multiple needs, from psychiatric support to rehabilitation, which should be reflected in their treatment. Of particular note is the use of ABC immunomodulatory drugs to prevent disease progression (Avonex/interferon beta-1a, Betaseron/interferon beta-1b and Copaxone/glatiramer acetate).

We have already seen that MS can be exacerbated by hormonal changes during the post partum period, and there is now evidence that women who use oral contraceptives have a 40% reduced risk of developing the disease compared with non-users. This study also found that women had a higher risk of developing the first symptoms of MS in the six months following a pregnancy, and a non-significant lower risk during pregnancy itself, compared with those who did not become pregnant.

Other topical research has concluded that brain damage continues to progress in patients who experience a clinically isolated MS syndrome, and 70.5 % will develop clinically definite MS within 5 years. At the same time, a blood test has been developed which can predict whether a single neurological event that could be MS will progress to an active form of the disease. In a retrospective study this new test correctly identified in advance the 36% of patients who went on to suffer additional attacks in the two year period following their first symptoms.

Perhaps the most important findings to emerge lately, however, confirm that a single cluster of genes on chromosome 6 comprises the only group to play a role in MS. These genes are associated with the major histocompatibility complex (MHC) which enables the body to distinguish between autologous cells and bacteria or other pathogens, and these results suggest that the likely cause of MS is interaction between a variation in the MHC system and environmental challenges.

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