Multiple sclerosis (MS) is a demyelinating disease of the central nervous system attacking the brain, spinal cord and both sensory and motor nerves. The cause of MS is unknown. Some as yet unidentified agent, enhanced by genetic and environmental factors, triggers a cascade of immunological etkinligini which ultimately results in the destruction of the fatty myelin sheath surrounding nerves and later the nerve axons themselves. Multiple plaques of scar tissue are formed where myelin has been attacked. This damage means nerves are unable to conduct impulses and the results can mean poor muscular co-ordination, impaired vision, speech and cognitive function, and poor bladder and bowel control depending on the nerves and brain area predominantly affected.
Estimates of the number of people affected by MS throughout the world vary between 1.11 and 2.5 million.1, 2 In western Europe, the number is estimated at 350,000, and in the US, 250,000. The UK figure is estimated at 85,000. [adapt to provide the appropriate national figure]
MS is one of the 100 disorders causing the greatest burden of disease worldwide.2
MS is predominantly a disease of temperate climates. It is distributed throughout the world in three zones of high, medium and low frequency.3 In the high frequency zone – Europe, Canada, the former USSR, Israel, Northern USA, New Zealand and SE Australia – prevalence rates are greater than 30 (mostly between 50 and 120) per 100,000. In the lowest frequency zone – Asia, Africa and South America – prevalence is less than 5 per 100,000.
The risk of developing MS in a high frequency zone is around 1 per 1,000.
MS affects women more than men in the ratio of about 2:1, possibly due to the influence of female sex hormones on the immune response.
Caucasians of European descent are affected much more frequently than other races, suggesting a genetic element.
The disease usually first affects people when they are young (aged between 20 and 40), typically manifesting itself around the age of 30.
MS is diagnosed on the basis of the patient's history of symptoms, a detailed neurological examination, magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) analysis.
According to the clinical pattern of relapses and residual disability experienced, patients are classified as having one of four patterns of MS, representing a continuum of disease:
Benign
Relapsing-remitting
Secondary progressive
Primary progressive
Benign MS
Patients stay relatively unimpaired for many years after an initial attack. Approximately 20 per cent of patients have this form of disease.
Relapsing-remitting MS
This is the usual pattern of disease in the first 20 years experienced by around 85 per cent of patients. They experience periodic attacks associated with some degree of impairment which subsequently resolves to a large degree if not completely. Around 25–35 per cent of patients have this pattern at any one time. More than 80% of patients progress from relapsing-remitting MS to the secondary progressive form.2
Secondary progressive MS
This form of the disease is marked by fewer remissions occurring after attacks and accumulating disability between relapses. An estimated 40 per cent of MS patients are in this category.
Primary progressive MS
This is characterised by a gradual, insidious and progressive deterioration with disability developing from the onset of disease without remissions. About 10 per cent or fewer MS patients have this condition.
The extent of a patient's neurological disability and deterioration is assessed, usually for clinical trial purposes, on the Kurtzke expanded disability scale (EDSS).4 This ranges from 0 (normal) to 10 (death) with the steps in between representing an increasing loss of neurological function. A score of 3 reflects moderate disability, 7 indicates a patient is wheelchair bound, and a score of 8, means bed bound.
Treatments for MS fall into three categories.
Acute
Symptomatic
Disease-modifying
Acute
Drugs used to treat acute exacerbations or relapses are usually the corticosteroids such as methylprednisolone. They reduce inflammation and shorten the time to recovery after a relapse. They do not affect the course of MS and in any case could not be taken long term because of their well-known side effects.
Symptomatic
Drugs used to control symptoms experienced by MS patients include those to ease pain, spasticity, depression, fatigue and urinary problems. Other non-drug treatments such as physiotherapy are helpful in teaching patients to circumvent the problems caused by MS.
Disease-modifying
The only drugs demonstrated to alter the natural course of MS include interferon beta-1b (Betaferon, Betaseron), interferon beta-1a (Avonex, Rebif) and glatiramer acetate (Copaxone). Of these, only Betaferon/Betaseron is licensed for the treatment of both relapsing-remitting and secondary progressive MS. Rebif, Avonex and, in some countries, Copaxone, are only indicated for use in patients with relapsing-remitting MS. All the interferon therapies and Copaxone have demonstrated an ability to reduce the number of expected relapses in relapsing-remitting MS. Only Betaferon/Betaseron has been able to demonstrate an ability to slow the progression of disease in secondary progressive MS and delay the onset of severe disability.
Interferons are cytokines with the capacity to modulate the etkinligini of the human immune system. For example, Betaferon prevents activated T-lymphocytes penetrating the blood brain barrier and intercepts to inhibit their destructive cascade of etkinligini.