Which of these diseases involves the destruction of the myelin sheath on certain neurons within the brain?

What research is being done?

Inhaltsverzeichnis Show

What is a myelin sheath?
What are the parts of a nerve cell?
What does the myelin sheath do?
What are the gaps in the myelin sheath called?
What happens when the myelin sheath is damaged?
What diseases cause damage to myelin?
Can damage to myelin be repaired?
Which of these diseases involves the destruction of the myelin sheath on certain neurons?
Which of these diseases involves the distraction of the myelin sheath on certain neurons within the brain and spinal cord?
What causes myelin sheath destruction?
What is the name of the disease in which the myelin sheaths of central nervous system axons are destroyed?

The NINDS funds research looking at many of the diseases and disorders that cause cerebral atrophy. Understanding the biological mechanisms that cause neurons to die in the brain will help researchers find ways to prevent, treat, and even cure the diseases that lead to cerebral atrophy.

Information from the National Library of Medicine’s MedlinePlus
Brain Diseases

Definition

Cerebral atrophy is a common feature of many of the diseases that affect the brain. Atrophy of any tissue means loss of cells. In brain tissue, atrophy describes a loss of neurons and the connections between them. Atrophy can be generalized, which means that all of the brain has shrunk; or it can be focal, affecting only a limited area of the brain and resulting in a decrease of the functions that area of the brain controls. If the cerebral hemispheres (the two lobes of the brain that form the cerebrum) are affected, conscious thought and voluntary processes may be impaired.

Associated Diseases/Disorders: The pattern and rate of progression of cerebral atrophy depends on the disease involved. Diseases that cause cerebral atrophy include:

stroke and traumatic brain injury
Alzheimer’s disease, Pick’s disease, and fronto-temporal dementia
cerebral palsy, in which lesions (damaged areas) may impair motor coordination
Huntington’s disease, and other hereditary diseases that are associated with genetic mutations
leukodystrophies, such as Krabbe disease, which destroy the myelin sheath that protects axons
mitochondrial encephalomyopathies, such as Kearns-Sayre syndrome, which interfere with the basic functions of neurons
multiple sclerosis, which causes inflammation, myelin damage, and lesions in cerebral tissue
infectious diseases, such as encephalitis, neurosyphilis, and AIDS, in which an infectious agent or the inflammatory reaction to it destroys neurons and their axons

Symptoms of cerebral atrophy: Many diseases that cause cerebral atrophy are associated with dementia, seizures, and a group of language disorders called the aphasias.

Dementia is characterized by a progressive impairment of memory and intellectual function that is severe enough to interfere with social and work skills. Memory, orientation, abstraction, ability to learn, visual-spatial perception, and higher executive functions such as planning, organizing, and sequencing may also be impaired.
Seizures can take different forms, appearing as disorientation, repetitive movements, loss of consciousness, or convulsions.
Aphasias are a group of disorders characterized by disturbances in speaking and understanding language. Receptive aphasia causes impaired comprehension. Expressive aphasia is reflected in odd choices of words, the use of partial phrases, disjointed clauses, and incomplete sentences.

What is a myelin sheath?

A myelin sheath is a sleeve (sheath) that’s wrapped around each nerve cell (neurons). It’s a protective layer of fat (lipids) and protein that coats the main “body” section of a neuron called the axon.

What are the parts of a nerve cell?

A nerve cell is called a neuron. Nerves cells make up your nervous system. Your nervous system is your body’s communication command center. It sends and receives communication from all parts of your body and reacts to changes inside and outside of your body.

Each nerve cell has three sections. The sections of a nerve cell can be thought of like a tree.

The soma, or cell body, is like the tree’s root system. The roots of the soma, called dendrites, receive the “nutrients” from the soil. The “nutrients” in this case are the chemical messages they receive from other nearby nerve cells. These messages are converted into electric impulses. The soma also contains the cell’s nucleus.
The axon is like the tree’s long trunk. The nutrients are transported from the tree’s roots up through the tree’s trunk. Similarly, the axon transports the impulses from the soma onward along its path.
The axon terminal is like the tree buds at the end of the tree’s branches. Leaves and pollen come out of these buds. The electrical impulses are sent (or “released” like pollen from a bud) to be picked up by the next nerve cell. This process keeps repeating as the impulse or message continues in its travels within your brain and spinal cord or out to your body. The result might be muscle fibers contracting to move your arm, help you breathe or keep your heart beating.

What does the myelin sheath do?

The myelin sheath has three functions:

Its fatty-protein coating provides protective insulation for your nerve cell, like the plastic insulation covering that encases the wires of an electrical cord.
It allows the electrical impulses to travel quickly and efficiently between one nerve cell and the next.
It maintains the strength of the impulse message as it travels down the axon.

Myelin is made by oligodendrocytes in your brain and spinal cord (your central nervous system [CNS]) and by Schwann cells in your peripheral nervous system. Your peripheral nervous system is the network of nerves outside of your CNS. These nerves communicate between your CNS and the rest of your body.

What are the gaps in the myelin sheath called?

Your myelin sheath isn’t one solid covering. It’s a lineup of individual sections of myelin, each separated from the next by a tiny gap — like the small amount of space you see between individual box cars on one long train. Each section of myelin is called an internode. Each gap in the myelin sheath — between internodes — is called the nodes of Ranvier. The nodes of Ranvier are rich in positive sodium ions. As the electrical signal or impulse travels along the axon, it jumps from one node to the next. When passing over the gap, the sodium ions recharge the electrical signal so it can continue in its travel without losing its charge or lessening in signal strength.

What happens when the myelin sheath is damaged?

About 100 billion nerve cells are in constant activity, sending and receiving messages that control every aspect of your body’s functioning. When your myelin sheath on nerve cells is damaged, the electrical signal is slowed or stopped.

Myelin can be damaged when your body’s immune cells think that myelin is a foreign substance. Your body’s immune system produces inflammatory substances that damage myelin and eventually kill the cells (the oligodendrocytes and Schwann cells) that make myelin. The location where the myelin is attacked determines your symptoms. The destruction of the myelin sheath is called demyelination.

What diseases cause damage to myelin?

Probably the most well-known disease that attacks the myelin in your central nervous system (brain and spinal cord) is multiple sclerosis.

Other central nervous system (CNS) diseases in which myelin is attacked include:

Acute disseminated encephalomyelitis. This is a rare, acute, intense immune reaction in the CNS.
Schilder’s sclerosis. This disease, also called diffuse myelinoclastic sclerosis, is a rare neurodegenerative disease in children.
Transverse myelitis.This is an autoimmune disorder that causes inflammation in your spinal cord.
Neuromyelitis optica. This is an antibody-mediated immune attack on your optic nerves and spinal cord.
Optic neuritis. This is another condition in which your eye nerves become inflamed.
Tumefactive demyelination. This is a single demyelinating lesion greater than 2 centimeters (cm).

Peripheral nervous system diseases in which myelin is attacked include:

Guillain-Barre syndrome.This immune disease could be caused by infections, including cytomegalovirus, Mycoplasma pneumonia, Epstein-Barr virus and influenza virus or vaccinations.
Chronic inflammatory demyelinating polyradiculoneuropathy. This is a slow-developing autoimmune disease that attacks myelin.
Paraproteinemic demyelinating neuropathy. This is a type of neuropathy associated with the presence of an antibody that is associated with malignancy.
Charcot Marie Tooth type 1 and type X. This is an inherited neuropathy.
Copper deficiency. Lack of copper leads to loss of protection of the myelin, making it susceptible to damage.

What other conditions can damage or destroy myelin?

A myelin sheath can also be damaged or destroyed in adults by:

Stroke.
Infections, immune and metabolic disorders.
Poisons.
Vitamin B12 deficiency.
Certain drugs, including ethambutol.
Excess alcohol intake.

In addition, in a few rare inherited diseases, the myelin sheath doesn’t properly form. These diseases include Tay-Sachs disease, Gaucher disease, Hurler syndrome and Niemann-Pick disease.

Can damage to myelin be repaired?

Damaged myelin can be repaired in both your central and peripheral nerve systems. It’s important to control the factors that cause demyelination such as inflammation, and immune suppression/modulation treatment, including steroids, intravenous immune globulin (IVIG) and other agents.

Scientists are making progress in understanding potential ways to promote myelin repair. Although there have been several promising studies, it still isn’t clear if the benefits seen were meaningful improvements for individuals, and there are currently no approved medications for myelin repair. Here are only some examples of studies:

A small phase II clinical trial has shown that the oral antihistamine clemastine has myelin-repairing qualities. Clemastine improved the transmission of the electrical signal in people with multiple sclerosis who had optic nerve damage. Another early human trial found that the diabetes drug metformin plus clemastine helped regenerate myelin.
Blocking a molecule in stem cells (the “building blocks” of all cell types) caused oligodendrocytes (the cells that make myelin in the CNS) to repair myelin and allowed mice with multiple sclerosis-like symptoms to achieve some degree of recovery.
Research studies continue to explore the potential role of stem cells in repairing myelin damage and slowing disease progression.
Other drugs are showing promise in protecting the nervous system from further damage. Ibudilast, an anti-inflammatory drug, significantly slowed the rate of brain cell death (atrophy) in a phase II trial. An epilepsy drug, phenytoin, was shown to be protective, resulting in 30% less damage to myelin compared with a placebo. Lipoic acid, an antioxidant, may help block nerve fiber damage.

A note from Cleveland Clinic

Myelin is an essential substance that keeps your nerves functioning, sending and receiving communication from all parts of your body. Without the100 billion functioning nerve cells, no part of your body would work. Many diseases and conditions can attack myelin — the best known is multiple sclerosis. Researchers continue looking for ways to protect, repair and regenerate myelin. The good news is that they’re making progress.

Which of these diseases involves the destruction of the myelin sheath on certain neurons?

Multiple sclerosis In this disorder, your immune system attacks the myelin sheath or the cells that produce and maintain it. This attack causes inflammation and injury to the nerve sheath and ultimately to the nerve fibers that it surrounds.

Which of these diseases involves the distraction of the myelin sheath on certain neurons within the brain and spinal cord?

In multiple sclerosis (MS), nerve conduction is disrupted by the destruction of the myelin sheath. The central nervous system or CNS is the part of the nervous system made up of the brain and spinal cord.

What causes myelin sheath destruction?

Myelin loss can occur as a result of direct damage to the myelin sheath or indirectly through a primary genetic disorder or attack on the OL during inflammation or toxic exposure. In addition, axon degeneration will lead to secondary loss of the myelin sheath (as in Wallerian degeneration).

What is the name of the disease in which the myelin sheaths of central nervous system axons are destroyed?

Multiple sclerosis is a debilitating disease of the central nervous system that has been characteristically classified as an immune-mediated destruction of myelin, the protective coating on nerve fibers.