Wallerian

Wallerian degeneration is a process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury. This is also known as anterograde or orthograde degeneration. A related process known as Wallerian-like degeneration occurs in many neurodegenerative diseases, especially those where axonal transport is impaired such as Alzheimer's and Parkinson's disease.

Process

Wallerian degeneration occurs after axonal injury in both the PNS and the CNS. The process is named after Augustus Volney Waller, a British neurophysiologist, who described the degeneration in 1850.

In the injured axon, the process begins immediately after the injury and the axonal skeleton and membrane break apart and form debris which is then cleaned up by phagocytes. In the PNS, the Schwann cells at the nerve ending proliferate and form a column of cells. The macrophages then come in and degrade the debris, allowing for the Schwann cells to guide the growth of new axons.

In the CNS, the process is different as the oligodendrocytes, which are the variant of Schwann cells, do not clean up the debris as quickly and efficiently, resulting in slower growth of new axons.

Clinical significance

Wallerian degeneration is seen in many conditions such as peripheral nerve injury, stroke, MS, ALS, and many others. Understanding this process is crucial for developing therapies for these conditions.

See also

• Axon
• Neuron
• Neurodegeneration
• Neuroregeneration

References

Wallerian Resources
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