Multiple Sclerosis: A Neurodegenerative Disease


Multiple Sclerosis, more commonly known as MS, is a disease in which the body’s immune system attacks the central nervous system. The central nervous system is composed of the brain, spinal cord, and optic nerves. In individuals with MS, the immune system causes inflammation in the central nervous system that damages the myelin sheath, the protective covering of nerve fibers (also known as axons), as well as the nerve fibers themselves. The axonal destruction unfortunately causes irreversible neurological damage, which is why Multiple Sclerosis is primarily considered a neurodegenerative disorder (Ciffeli et al., 2002). Myelin is a fatty substance that surrounds, insulates, and protects the axons. Therefore, when the myelin sheath is damaged or destroyed, the central nervous system’s ability to send and receive messages is altered or stopped completely. The resulting damaged areas then develop scar tissue, which is where the disease gets its name — multiple areas of scarring or multiple sclerosis (condition of hardening or scarring).

Multiple Sclerosis is still widely regarded as a disease of the white matter in the brain, but recent evidence shows that there may be significant involvement of gray matter too (Boraschi et al., 2002). Grey matter contains nerve cell bodies, dendrites, and axon terminals of neurons (Villines, 2018). The gray matter is where all the synapses are. A synapse is the intersection between two dendrites. White matter, on the other hand, is where axons connect different areas of gray matter. Impulses are carried from the cell body through the dendrites, into the synapse. There, the axon from the receiving cell will pick up the impulse. In this process, the job of white matter is to conduct, process, and send nerve signals up and down the spinal cord. Therefore, damage to the white matter of your brain or spinal cord can affect your ability to move, use your sensory faculties, or react appropriately to external stimuli. Some people with damaged white matter may also experience deficits in reflexive reactions (Villines, 2018).

The damage to various areas of the central nervous system produces a variety of neurological symptoms that vary based on severity. Common symptoms of MS may include fatigue, numbness or tingling, difficulty walking, spasticity, and cognitive dysfunction, while less common symptoms may include speech problems, swallowing and breathing problems, tremors, seizures, and hearing loss (National Multiple Sclerosis Foundation).

While the cause of multiple sclerosis is still unknown, scientists believe it is triggered by a combination of factors. Therefore, research is ongoing in the areas of immunology (the study of the immune system), epidemiology (the study of disease patterns in large groups of people), and genetics (understanding genes that may not be functioning correctly in people who develop MS). Infectious agents are also being studied to see if there is a correlation between infections and multiple sclerosis. While there is no single risk factor that has been identified, a variety of factors are believed to contribute to the overall risk of developing multiple sclerosis.

Among these “risk factors” are geographical location, insufficient levels of vitamin D , smoking history, and obesity. For example, multiple sclerosis is known to occur more frequently in individuals who live in areas further from the equator. Data also suggests that exposure to some environmental agents before puberty may predispose an individual to develop multiple sclerosis. In addition, growing evidence has shown that low vitamin D levels are a risk factor for developing multiple sclerosis. Sunlight is a natural source of vitamin D, and areas closer to the equator are exposed to greater amounts of sunlight year-round than people living closer to the north and south poles. Another risk factor is smoking. As with many other diseases, smoking increases the risk for developing multiple sclerosis, and also increases the progression of the disease. Fortunately, the evidence also suggests that quitting smoking is associated with reduced risk and a slower progression of the disease. Lastly, childhood and adolescent obesity, particularly in females, may increase one’s risk of developing multiple sclerosis later on in life.

Although multiple sclerosis is not an inherited disease, there is a genetic risk factor associated with it. The probability of developing multiple sclerosis increases if a first degree relative (mother, father, siblings, children) has the disease. In identical twins, if one twin has the disease, the other twins risk for developing MS is about one in four. Approximately 200 genes have also been identified as contributing a small amount to the overall risk of developing multiple sclerosis, but additional research needs to be done to better understand these factors that contribute to the development of this disease.

Multiple sclerosis is thought to affect more than 2.3 million people worldwide. While the disease is not contagious or directly inherited, epidemiologists have identified factors in the distribution of MS around the world that may eventually help determine what causes the disease (National Multiple Sclerosis Foundation). These factors include gender, genetics, age, geography and ethnic background. Most people are diagnosed between the ages of 20 and 50, and although MS can occur in young children it is more prevalent in older adults. MS is at least two to three times more common in women than in men, thereby suggesting that hormones may also play a significant role in determining an individual’s susceptibility to acquiring multiple sclerosis. Overall, MS is a debilitating neurodegenerative disease that renders an individual unable to go about their day to day activities without experiencing pain and other symptoms. While no cure currently exists, there are various treatment options that can be utilized to treat the symptoms of this disease and improve one’s quality of life.

References

Boraschi, D., & Penton-Rol, G. (2016). Immune rebalancing: The future of immunosuppression. Amsterdam: Elsevier/Academic Press.

Cifelli, A., Arridge, M., Jezzard, P., Esiri, M. M., Palace, J., & Matthews, P. M. (2002). Thalamic neurodegeneration in multiple sclerosis. Annals of Neurology,52(5), 650-653. doi:10.1002/ana.10326

National Multiple Sclerosis Society. (n.d.). What Is MS? Retrieved from https://www.nationalmssociety.org/What-is-MS  

Villines, Z. (2018, August 02). Gray Matter vs. White Matter in the Brain. Retrieved from https://www.spinalcord.com/blog/gray-matter-vs-white-matter-in-the-brain

 

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    Zafar Khan MD

    It is a very interesting work. As suggested in the text , it t still remains poorly understood. The author has made a great effort in making it easy to understand. I wish to o congratulate the author for this beautiful work.

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