Wallerian degeneration is an important concept that is useful in
mapping the anatomic components of peripheral nerves and spinal cord segments
, in recognizing peripheral or central nervous system disorders microscopically, and in understanding and predicting reinnervation by peripheral nerves.
Is Wallerian degeneration retrograde?
Wallerian degeneration is
an active process of retrograde degeneration of the distal end of an axon
that is a result of a nerve lesion. It occurs between 7 to 21 days after the lesion occurs.
What is anterograde degeneration?
Anterograde degeneration occurs
when the axon distal to the site of injury degenerates
. This usually begins within 24 hours and completes within 7 days of insult. The proximal part of the axon, still connected to the cell body, remains normal in appearance and function for 3–4 weeks.
What happens during axonal degeneration?
Axonal degeneration refers to
loss of integrity of axonal processes
and may occur following injury that directly affects axons, or secondary to changes targeting myelin sheaths.
What is dying back axonal degeneration?
Dying-back refers to
the progressive distal to proximal axonal degeneration that results from metabolic, toxic, or degenerative disorders
. … The discovery of the mouse WlD
s
mutant, which has prolonged axonal survival following nerve transection, indicates that axons contain an intrinsic protective mechanism.
What is the major difference between anterograde degeneration and retrograde degeneration?
Retrograde degeneration occurs when
the proximal segment starts to degenerate and all affected RGCs die by 6–8 weeks
. Ascending optic atrophy is characterized by degeneration of the RGC axons at the level of the optic nerve head by the anterograde mechanism.
Is Wallerian degeneration progressive?
We conclude that Wallerian degeneration
progresses rapidly along
individual wild-type axons after a heterogeneous latent phase. The speed of progression and its ability to travel in either direction challenges earlier models in which clearance of trophic or regulatory factors by axonal transport triggers degeneration.
Is Wallerian degeneration painful?
Wallerian degeneration and neuropathic pain. Wallerian degeneration is a stereotype reaction of
the peripheral nervous system to different
kinds of nerve injury. This auto-destructive process is frequently associated with neuropathic pain, which can be very severe and resistant to treatment.
What does Neurotmesis mean?
Neurotmesis is
a complete transection of a peripheral nerve
. The severity of peripheral nerve injury can be classified as neurapraxia, axonotmesis, or neurotmesis. Neurotmesis will produce complete sensory and motor deficits to the skin and muscles innervated by the injured nerve.
How long does it take for Wallerian degeneration?
It begins 3 to 4 days after the injury and is
completed after 12 to 14 days
. Myelin destruction and removal are delayed considerably during slow Wallerian degeneration in Wld
s
mice, as are axon destruction and macrophage recruitment [16,17,42,60].
What is axonal disease?
Giant axonal neuropathy is
an inherited condition characterized by abnormally large and dysfunctional axons called
giant axons. Axons are specialized extensions of nerve cells (neurons) that transmit nerve impulses.
What is degenerative nerve damage?
Degenerative nerve diseases affect many of your body’s activities, such as
balance, movement, talking, breathing, and heart function
. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses.
What does axonal mean?
(ăk′sŏn′) also ax·one (-sōn′) n.
The usually long process of a nerve fiber that generally conducts impulses away from the body of the nerve cell
.
Which conditions cause damage to axon?
Axon Growth and Regeneration: Part 1
The mechanisms of axonal injury depend on the disease and include
ischemia, inflammation, compression, and trauma
. The final common pathway of axonal injury is processes of retrograde and Wallerian degeneration, autonomous processes separate from apoptosis.
What causes axon loss?
As shown schematically (D), axonal degeneration can occur as a consequence of chronic demyelination. Oligodendrocyte-derived factors have a trophic effect on axons. The
lack of
trophic support (D1) may cause axonal transection and Wallerian degeneration distally (D2) or retrograde neuronal death (D3).
What are axons responsible for?
An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron’s cell body or soma. Axons are in
effect the primary transmission lines of the nervous system
, and as bundles they help make up nerves.
