Transverse myelitis

Definitions & Key takeaways

Transverse myelitis is a neurological disorder characterized by an inflammation that damages the myelin as well as the rest of the neurons across a section of the spinal cord. It's a rare disease that can be triggered by an infectious or autoimmune process.

The symptoms are related to the affected part of the spinal cord. When the corticospinal tract is affected a person will have problems with voluntary movement, and when the spinothalamic tract is damaged a person will have problems sensing pain. If it is the dorsal column pathway that is damaged, a person will have problems with balance and spatial orientation.

Diagnosis can be done with a lumbar puncture which is when a needle is used to collect and analyze cerebrospinal fluid from around the spinal cord. In addition, an MRI, or magnetic resonance imaging, can be used to spot areas of inflammation in the spinal cord. Treatment of transverse myelitis depends on the underlying cause. If there's an autoimmune process, it may be helpful to use steroids or plasmapheresis, which is where antibodies are filtered out of the blood.

Chapters:

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Introduction0:00–0:27

The name of the disorder transverse myelitis can be broken down. Transverse means extending completely across something - in this case, it refers to going across the spinal cord, and myelitis means inflammation of myelin which is the fatty substance surrounding nerves.
So, in transverse myelitis there’s inflammation that damages the myelin as well as the rest of the neuron across a section of the spinal cord.

Physiology0:27–3:07

Now, neurons are the main cells of the nervous system. They’re composed of a cell body, which contains all the cell’s organelles, and nerve fibers, which are projections that extend out from the neuron cell body.
Nerve fibers are either dendrites that receive signals from other neurons, or axons that send signals along to other neurons.
Where two neurons come together is called a synapse, and that’s where one end of an axon sends neurotransmitters to the dendrites or directly to the cell body of the next neuron in the series.
The axons are intermittently wrapped in a fatty substance called myelin. Myelin is extremely important to neurons, because it helps to allow an action potential to propagate much faster.
An action potential is an electrical signal that races down the axon, triggering the release of neurotransmitters or a chemical signal, on the other end.
Without myelin this signal propagation is very slow and inefficient. Since some of these neurons can be very long, especially ones that go from the spinal cord to the toes, the fact that myelin helps speed up action potentials is super important!
Now, the spinal cord is composed of both grey and white matter. Grey matter consists of cell bodies.
It’s in the the middle of the spinal cord and is shaped like a butterfly. Surrounding the grey matter is white matter, which consists of the myelinated axons of various neurons.
The neurons in the spinal cord form different neural tracts that carry information to and from the brain. There are three main tracts to remember.
The corticospinal tract is a descending pathway that carries motor information from the brain to different muscles in the body and it controls voluntary muscle movement.
The dorsal column is an ascending pathway that carries sensory information about pressure, vibration, fine touch, and proprioception--or the awareness of one’s bodily position in space.
Finally, the spinothalamic tract is another ascending pathway and it’s divided into two parts. The lateral tract carries sensory information for pain, pressure, and temperature, while the anterior tract carries information for crude touch--or the sense one has been touched, but without being able to localize where they were touched.
Autonomic neurons are also located in the spinal cord--these help regulate processes like urination, digestion, and heart rate.
These neurons hitch a ride with the various tracts, but their cell bodies are found in the spinal cord. For example, the sympathetic division, or the fight response, has its cell bodies in the thoracic and lumbar regions and make up the lateral horns of the grey matter.

Pathology3:07–3:59

In transverse myelitis there’s inflammation of the spinal cord across an entire spinal cord segment, or even multiple segments in some instances.
Most commonly, the inflammation occurs at the thoracic level but can also occur in the cervical and lumbar regions as well.
The inflammation may be caused by an infection, an autoimmune disease like multiple sclerosis, or it could just be idiopathic, meaning there is no identifiable cause.
Some well known pathogens that trigger inflammation include mycoplasma pneumonia, herpes and dengue viruses, and schistosomiasis - a parasitic disease.
Ultimately the inflammation damages the myelin or the neurons themselves in the spinal cord. When this occurs, neurons become unable to communicate with one another and messages going up and down the spine fail to get delivered.

Symptoms3:59–4:35

Symptoms of transverse myelitis depend on which tracts are damaged - and usually affect sensory, motor, or autonomic function on both sides of the body.
There’s usually a well defined sensory level - meaning that the symptoms only affect the body below a certain level of the spinal cord.
Damage to the corticospinal tract causes weakness and problems with voluntary muscle movement below the level of the spinal cord segment.
Damage to the spinothalamic tract causes a loss of temperature and pain sensation. And damage to the dorsal-column pathways causes problems with balance and spatial orientation.

Diagnosis4:35–4:57

Diagnosis of transverse myelitis can be done with a lumbar puncture which is when a needle is used to collect cerebrospinal fluid from around the spinal cord.
In transverse myelitis there’s usually an increase in white blood cells. In addition, an MRI, or magnetic resonance imaging, can be used to spot areas of inflammation in the spinal cord.

Treatment4:57–5:11

Treatment of transverse myelitis depends on the underlying cause. If there’s an autoimmune process, it may be helpful to use steroids or plasmapheresis, which is where antibodies are filtered out of the blood.

Review5:11–6:41

All right, as a quick recap transverse myelitis is inflammation across a certain level in the spinal cord. It’s a rare disease which can be triggered by an infectious or autoimmune process.
The symptoms are related to the affected part of the spinal cord. When the corticospinal tract is affected a person will have problems with voluntary movement, and when the spinothalamic tract is damaged a person will have problems sensing pain.
Lastly, if the dorsal column pathway is damaged, a person will have problems with balance and spatial orientation.