Transverse myelitis
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Transverse myelitis
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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.
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 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.
Resumen
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.
Fuentes
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Transverse myelitis" Autoimmunity Reviews (2012)
- "Immunopathogenesis of acute transverse myelitis" Current Opinion in Neurology (2002)
- "Central Pattern Generator for Locomotion: Anatomical, Physiological, and Pathophysiological Considerations" Frontiers in Neurology (2013)