Wallerian

Wallerian is an adjective used in neuroscience to denote relations to the process named after the English physiologist Augustus Volney Waller. The term is most commonly encountered in Wallerian degeneration, a form of anterograde axonal degeneration that follows injury to a nerve.

After an axon is cut or crushed, the portion distal to the injury loses its connection to the cell body and degenerates. The breakdown of the axonal cytoskeleton is followed by disintegration of the axon and its myelin sheath. In the peripheral nervous system, Schwann cells and macrophages rapidly clear debris and help create a permissive environment for regeneration by guiding regrowing axons through Büngner bands. In the central nervous system, regenerative capacity is limited by inhibitory signals and glial scarring, so distal degeneration is often followed by little true regrowth after injury.

Clinical and research relevance: Wallerian degeneration can be observed histologically and, in many cases, on imaging after nerve injury. It helps explain patterns of sensory and motor loss and is used in understanding, diagnosing, and staging peripheral neuropathies, spinal cord injuries, and brain injuries that involve long neural tracts.

History: The phenomenon was first described by Augustus Waller in the 1850s. The term Wallerian degeneration was later formalized to describe the distal degeneration of axons following injury and the subsequent cellular responses.