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Home , Demyelinating disease, Multiple sclerosis

Demyelination: What Is It and Why Does It Happen?

• Causes • Symptoms • Types • MS and Demyelination • Treatment and Diagnosis • • Takeaway

What is demyelination? send and receive messages from every part of your body and process them in your brain. Nerves allow you to speak, see, feel, and think. Many nerves are coated in . Myelin is an insulating material. When it’s worn away or damaged, nerves can deteriorate, causing problems in the brain and throughout the body. Damage to myelin around nerves is called demyelination.

Nerves Nerves are made up of . Neurons are composed of a cell body, dendrites, and an . The axon sends messages from one to the next. The axon also connects neurons to other cells, such as muscle cells. Some are extremely short. Others are 3 feet long. Some axons are covered in myelin. Myelin protects the axons and helps carry axon messages as quickly as possible.

Myelin Myelin is made of membrane layers that cover an axon. This is similar to the idea of an electrical wire with coating to protect the metal underneath. Myelin allows a signal to travel faster. In unmyelinated neurons, a signal can travel along the nerves at about 1 meter per second. In a myelinated neuron, the signal can travel 100 meters per second. Certain can damage myelin. Demyelination slows down messages sent along axons and causes the axon to deteriorate. Depending upon the location of the damage, axon loss can cause problems with feeling, moving, seeing, hearing, and thinking clearly.

CAUSES Causes of demyelination

Inflammation is the most common cause of myelin damage. Other causes include: • certain viral • metabolic problems • loss of oxygen • physical compression

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SYMPTOMS Symptoms of demyelination

Demyelination prevents nerves from being able to conduct messages to and from the brain. The effects of demyelination can occur rapidly. In Guillain-Barre syndrome (GBS), myelin may only be under attack for a few hours before symptoms appear.

Symptoms can come and go in chronic illnesses like (MS) and progress over years. Nerves are a key part of your body functions. Thus, a wide range of symptoms can occur when nerves are affected by demyelination, including: • numbness • loss of reflexes and uncoordinated movements • poorly controlled blood pressure • • • racing heart beat or palpitations • memory problems • • loss of bladder and bowel control •

Early symptoms of demyelination

Not everyone is affected by demyelinating diseases in the same way. However, some demyelinating symptoms are very common. Early symptoms include: • loss of vision • bladder or bowel problems • unusual nerve pain • overall fatigue These are among the first signs of a demyelinating .

TYPES Types of demyelination

There are different types of demyelination. These include inflammatory demyelination and viral demyelination.

Inflammatory demyelination Inflammatory demyelination happens when the body’s immune system attacks myelin. Types of demyelination like MS, optic , and acute-disseminated are caused by in the brain and . GBS involves inflammatory demyelination of peripheral nerves in other parts of the body.

Viral demyelination Viral demyelination occurs with progressive multifocal leucoencephalopathy

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(PML). PML is caused by the JC . Myelin damage can also occur with alcoholism, liver damage, and electrolyte imbalances. Hypoxic-ischemic demyelination occurs due to a lack of oxygen or vascular disease in the brain.

MS AND DEMYELINATION Demyelination and multiple sclerosis

MS is the most common . According to the National MS Society, it affects 2.3 million people worldwide. In MS, demyelination occurs in the of the brain and in the spinal cord. Lesions or “plaques” then form where myelin is under attack by the immune system. Many of these plaques (or scar tissue) occur throughout the brain over the course of years.

The types of MS are: • Clinically Isolated Syndrome • relapsing-remitting MS • primary-progressive MS • secondary-progressive MS

TREATMENT AND DIAGNOSIS Treatment and diagnosis

There is no cure for demyelinating diseases. New myelin growth can occur in areas of damage. But new myelin is thinner and not as effective. Researcher are looking into ways to increase the body’s ability to grow new myelin. Most treatments of demyelinating disease reduce the immune response. This is done with drugs like beta-1a or . Also, people with low levels of vitamin D more easily develop MS or other demyelinating diseases. High levels of vitamin D may reduce inflammatory immune response. Demyelination MRI Demyelinating diseases, especially MS and (inflammation of the ), are detectable with MRI scans. MRIs can show demyelination plaques in the brain and nerves, especially those caused by MS. Your doctor may be able to locate plaques or lesions affecting your . Then, treatment can be directed specifically at the source of demyelination in your body.

A closer look: Multiple sclerosis MRI images of the brain »

A note on The (CNS) is able to produce its own . Current studies show that if you take statins to reduce the cholesterol in your body, they are not likely to affect your CNS cholesterol. Many studies have also found that treatment may protect against Alzheimer’s Disease (AD) in patients who have not already experienced cognitive impairment and are still relatively young. Researchers have found that statins may slow the rate of cognitive decline and delay the onset of AD. Research continues, and we don’t have a definite answer yet. Some studies show that statins do not affect the CNS or , and 3 still others say they do. Currently, most of the evidence does not show statin therapy to be harmful to remyelination within the CNS. Still, the effects of statins on cognitive function remain controversial at this time.

VACCINES Vaccines and demyelination

Activating the immune system with a can trigger an autoimmune reaction. This tends to occur only in a few individuals with hypersensitive immune systems. Some children and adults experience “acute demyelinating syndromes” after exposure to certain vaccines, such as those for or HPV. But there have only been 77 documented cases since 1979.

TAKEAWAY The takeaway

Demyelinating diseases can seem painful and unmanageable at first. However, living with MS and other common demyelinating disease does not have to be a terrible experience. There is promising new research about the causes of demyelination and how to treat the biological sources of myelin deterioration. Treatments are also being improved for the management of pain caused by demyelination.

Demyelinating diseases may not be curable. However, talking to your doctor about medications and other treatments may help you learn more about your condition. The more you know, the more you can address the symptoms by changing your lifestyle to confront the pain. When you can keep the symptoms of demyelination in check, you can feel peace of mind knowing how to control it.

Article resources • Berghoff, S. A., Gerndt, N., Winchenbach, J., Stumpf, S. K., Hosang, L., Odoardi, F., … & Liebetanz, D. (2017). Dietary cholesterol promotes repair of demyelinated lesions in the adult brain. Nature communications, 8 • nature.com/articles/ncomms14241 • Bettermann, K., Arnold, A. M., Williamson, J., Rapp, S., Sink, K., Toole, J. F., … Burke, G. L. (2012, August). Statins, risk of and cognitive function: Secondary analysis of the ginkgo evaluation of memory study [Abstract]. Journal of and Cerebrovascular Diseases, 21(6), 436- 444 • ncbi.nlm.nih.gov/pubmed/21236699 • Chari, D. M. (2007). Remyelination in multiple sclerosis. International Review of Neurobiology, 79, 589-620 • sciencedirect.com/science/article/pii/S0074774207790268 • Demyelinating diseases of the nervous system. (2008) • dartmouth.edu/~dons/part_3/chapter_23.html • Guillain-Barré Syndrome [Fact sheet]. (2015, November 19)

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• ninds.nih.gov/disorders/gbs/detail_gbs.htm • and multiple sclerosis. (2015, August 28) • cdc.gov/vaccinesafety/Vaccines/multiplesclerosis_and_hep_b.html • Hesselink, J. R. (n.d.). Demyelinating diseases of the brain • spinwarp.ucsd.edu/NeuroWeb/Text/br-840.htm • Karussis, D., & Petrou, P. (2014, March) The spectrum of post- inflammatory CNS demyelinating syndromes. Reviews, 13(3), 215-224 • sciencedirect.com/science/article/pii/S156899721300178X • Kremer, D., Göttle, P., Hartung, H. P., & Küry, P. (2016, April). Pushing forward: Remyelination as the new frontier in CNS diseases. Trends in Neurosciences, 39(4), 246-263 • cell.com/trends/neurosciences/fulltext/S0166-2236(16)00028-X • McFarland, A. J., Anoopkumar-Dukie, S., Arora, D. S., Grant, G. D., McDermott, C. M., Perkins, A. V., & Davey, A. K. (2014, November 10). Molecular mechanisms underlying the effects of statins in the central nervous system. International Journal of Molecular Sciences, 15(11), 20607-20637 • ncbi.nlm.nih.gov/pmc/articles/PMC4264186/ • Olson, J., & Hall, S. (2013, May 1). Vitamin D reduces development and progression of virus-induced demyelinating disease. The Journal of , 190(137), 7 • jimmunol.org/content/190/1_Supplement/137.7 • Scheller, N. M., Svanström, H., Pasternak, B., Arnheim-Dahlström, L., Sundström, K., Fink, K., & Hviid, A. (2015, January 6). Quadrivalent HPV vaccination and risk of multiple sclerosis and other demyelinating diseases of the central nervous system. Jama, 313(1), 54-61 • jamanetwork.com/journals/jama/fullarticle/2088853 • Susuki, K. (2010). Myelin: A specialized membrane for cell communication. Nature Education, 3(9), 59 • nature.com/scitable/topicpage/myelin-a-specialized-membrane-for-cell- communication-14367205 • Swanson, J. W. (2014, June 3). What are the types of demyelinating disease that affect the central nervous system and what can you do about them? Retrieved from • mayoclinic.org/demyelinating-disease/expert-answers/faq-20058521/ • What is MS? (2016, November 10) • msif.org/about-ms/what-is-ms/ • What is myelin? (2016) • nationalmssociety.org/What-is-MS/Definition-of-MS/Myelin • Who gets MS? (2016) • nationalmssociety.org/What-is-MS/Who-Gets-MS

Source: https://www.healthline.com/health/multiple-sclerosis/demyelination#vaccines

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