A demyelinating disease is any nervous system condition that damages the myelin sheaths of neurons. These sheaths cover many nerve fibers throughout the body and play important roles in nerve transmission. As such, demyelination can have serious neurological consequences. Many diseases involve demyelination, and there are several classifications for these diseases, depending on which nerves they affect and how. Demyelination can have many symptoms, depending on the disease, affected region, and other factors.
Nerves send and receive signals from all over the body and then process them in the brain, allowing humans to see, feel, smell, speak, and think. Nerves consist of neurons with a cell body, dendrites, and axons. The latter send messages between neurons and connect them to other cells. The myelin sheath protects the axons and allows signals to travel faster. Depending on where and how myelin forms, the sheaths differ chemically and immunologically. This is where the classifications for demyelinating diseases originate. Demyelination refers to damage to the myelin that does not damage the axons. It tends to be segmental or patchy, meaning that it affects multiple areas.
Researchers are still attempting to understand how and why demyelination occurs. Inflammation plays a major role in damaging the sheath, but the trigger is unclear. Some experts believe that genetics and environmental factors such as infections or exposure to chemicals are responsible. Studies show that organophosphate poisoning from weed killers and insecticides can cause nerve demyelination. It’s also possible that vitamin B12 deficiency is responsible. Genetics, autoimmune reactions, infectious agents, and other unknown issues can all cause demyelination disease.
Demyelination may affect a person in many ways, depending on the location of the issue, though people often share similar symptoms. If demyelination affects the spinal nerves, bladder and bowel issues are usually the first to develop. Demyelination in the brain has a wide range of effects, often led by vision issues. Other early signs include unusual or unexplainable nerve pain, as well as general weakness and tiredness.
In addition to the general effects of demyelination, each demyelinating disease has unique symptoms. Depending on the condition, these symptoms may wax or wane in severity. They include
Traditionally, experts recognize two categories of demyelination: demyelinating myelinoclastic diseases and demyelinating leukodystrophy diseases. The first involves myelin destruction, while the second results from myelin failure or an inability to create myelin. Because of this, many experts view the second category as separate from demyelination. Additionally, researchers further classify demyelination by cause. Some of these subtypes are simplistic and overlap with other causes, but this helps provide a framework for accurate diagnoses.
Among the various categories for demyelinating diseases, inflammatory demyelination is among the most common and best understood. Three major diseases fall into this category: multiple sclerosis, acute hemorrhagic leukoencephalitis, and acute disseminated encephalomyelitis. Their effects are highly variable and wide-reaching. Viral demyelination is less common, but its cause, the JC virus, is incredibly widespread. Around 50% of children and 75% of adults have a JC virus infection, though most cases are asymptomatic. HIV may also cause demyelination. Viral demyelination usually affects motor function, vision, personality, cognition, and speech.
There are several other types of demyelination, though they are much rarer. Acquired metabolic demyelination occurs due to central pontine myelinolysis and extrapontine myelinolysis. Rarely, demyelination may develop alongside chronic alcoholism and malnourishment. Normally, brain tissue undergoes necrosis when it does not receive enough oxygen, or there is reduced blood flow, but sometimes it causes hypoxic-ischemic demyelination.
Some people have hypersensitive immune systems; activating their immune system with a vaccine triggers an autoimmune reaction. Some of these individuals experience acute demyelinating syndromes following vaccinations for influenza or HPV. This has led to increasing claims that vaccines are harmful and unsafe. However, this reaction is extremely rare, with only 71 cases between 1979 and 2014. Additionally, there is not sufficient evidence that vaccines are responsible for the demyelination.
Doctors can discover signs of demyelination and diagnose related diseases in many ways. Some diseases, such as multiple sclerosis, cause the growth of demyelination plaques in the brain and nerves, which appear on MRI scans. Additionally, doctors may assume demyelination due to several existing factors, including
There is no effective, specific treatment for demyelination. However, affected regions of the body can begin to heal as they undergo remyelination. To prompt this healing, doctors will treat the underlying disease or issue that triggered the demyelination. Most treatments involve dampening the immune response to prevent ongoing myelin sheath damage. Additionally, some physicians may prescribe vitamin D supplements to protect against demyelinating diseases and their effects. This may also reduce inflammatory immune responses.
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