Wallerian degeneration

Orderly anterograde breakdown of an axon → myelin distal to a focal injury that interrupts axonal transport.

Sequelae

PNS: Schwann cells proliferate → form guiding tubes and secrete growth factors → axons regenerate along their original path.

CNS: Inhibitory myelin proteins and astrocytic glial scar prevent meaningful regrowth → tract atrophy and gliosis → appears as T2 hyperintensity and chronic volume loss along affected tracts on MRI.