Multiple Sclerosis (MS), also known as demyelinating disease, is an autoimmune disease in which the body’s immune system attacks the central nervous system, particularly the brain and spinal cord. Inflammation of the nerves causes damages to the myelin sheaths which surround neurons. Since myelin acts as an electrical insulator, damage to the sheaths inhibits the ability of the neurons to fire properly. MS can affect anyone, but women are more susceptible to it than men. It can occur during any stage of life, but it is most common after adolescence and before 50. While exact figures are difficult to predict, it’s estimated that 250,000 to 350,000 people in the United States have MS.
Although MS attacks the nervous system in the same way, there are different types of progression to the disease that have been observed in patients. These forms of MS progression have been categorized into 4 major categories or subtypes:
- Relapsing-Remitting: Patients have extended periods of remission, often months to years, with little to no signs of disease progression, punctuated by sudden and unexpected relapses in the form of attacks from the disease.
- Primary Progressive: Patients show a consistent increase in disease activity with little to no remission, nor sudden attacks from the disease.
- Secondary Progressive: Patients show a consistent increase in disease activity without remission but with sudden attacks from the disease. Many patients who demonstrated relapsing-remitting progression have their MS convert to this type of progression when they lose periods of remission.
- Progressive relapsing: Patients show a consistent increase in disease activity from the onset of the illness without any remission and accompanied by unexpected attacks from the disease.
There are also variants of MS, referred to as idiopathic inflammatory demyelinating diseases that do not conform to any of progression patterns above, but exhibit similar symptoms. It is not clear if they are genuine forms of MS, other diseases, or whether there is a spectrum of diseases in which MS is situated.
Signs and Symptoms
Since MS affects the central nervous system, signs and symptoms of the disease can include anything neurological in nature:
- Loss of sensation or numbness
- Difficulty in coordination or movement
- Poor balance
- Speech problems
- Visual impairments
- Bladder/Bowel problems
- Mood swings
- Mental impairments
Symptoms of MS occur either in sudden attacks (relapses) or in a steady decline of neurological functioning, or a mixture of both.
There is no known definitive cause of MS, although there are several theories. There may be a partial genetic component to the disease since having a family member with the disease increases one’s overall risk of developing it. It is not directly hereditary, however. Some races and ethnicities have greater incidence rates of MS than other, again suggesting that genes play a role in its development. Research suggests that individuals with certain variants of Chromosome 6, which contains over 100 different genes governing the immune system, are more susceptible to the disease than individuals without the variants.
There are also several environmental factors that may influence the development of MS. It’s known that the farther one is from the equator, the greater the risk for developing MS. This might suggest that exposure to sunlight and levels of Vitamin D (the “sunshine” vitamin) may be related to the disease. Other environmental factors that may be associated with MS include exposure to industrial chemicals such as solvents, smoking, diet, and stress.
Infections from pathogens, microbes, or viruses are also theorized to be triggers for MS. It is believed that early exposure to certain infections may protect against MS later in life by creating autoimmune responses via antibodies. Individuals who were not exposed to these infections early in life may develop MS later on, triggered by later infections for which they have no autoimmune response. It has been observed that in developing countries, where there is a greater likelihood of exposure to infectious agents during childhood, there is less prevalence of MS. This is known as the hygiene theory, and it suggests why MS develops more in industrialized countries and why the disease usually develops post-adolescence.
As of right now, the most commonly accepted explanation of the disease is that there is a genetic component that may predispose certain individuals to the disease and that unknown environmental factors contribute to the expression of the disease in those individuals.
Since there are many diseases that are autoimmune, inflammatory, and/or neurological in nature, the signs and symptoms of MS are very similar to other conditions. As a result, MS can be very difficult to diagnosis. There have been historical criteria used to establish the presence of the disease, although they relied heavily on outward symptoms of the disease. In 2001, experts in MS revised the criteria for diagnosing MS to include MRI imaging to detect the lesions and scarring associated with MS, although some argue that only biopsy or autopsy can definitively diagnose the disease. The 2001 revised criteria are known as the McDonald criteria and are considered the “gold standard” for diagnosing MS.
There is no known cure for MS, although there are several therapies and medications used to treat the disease. They’re used to restore certain neurological functions after an acute attack of MS and/or to prevent further attacks or disabilities cause by attacks. One common treatment right after an attack is the administration of corticosteroids for several days. This has been shown to relieve symptoms in the short term but is not beneficial in slowing the long-term progress of the disease.
When patients show an isolated attack of a single symptom, administration of the proteins known as interferons has shown promise in stopping further progression of the isolated symptoms into genuine MS. Another treatment is a mixture of polypeptides known as copaxone, which mimics the appearance of myelin to the immune system, and if injected daily can help protect myelin by substituting as the target of the immune system’s attack response. Other treatments include drugs such as mitoxantrone and natalizumab, which help by suppressing the body’s natural immune response.
Since there is no cure for MS, it continues to advance and attack the myelin sheaths for decades after the initial onset of the disease. On average, individuals with MS die 5 to 10 years earlier than those without the disease; 30 years is the average duration of time until death after the onset of the disease. Different subtypes of MS along with the kinds of symptoms and the gender and ethnicity of the patient will all affect the long-term progression of the disease. Over 1/3 of MS patients live past 60, but 2/3 of patients will die from complications of the disease. Rates of suicide are higher in populations of MS patients than the general population.
Links and Resources