Wallerian degeneration can be observed following stroke, brain tumor, brain surgery or radiation and trauma. It typically affects the descending corticospinal tract but long association and commissural fibers can also be affected. In the acute phase the affect fiber tract can demonstrate restricted diffusion or enhancement. More typically in the acute and subacute phases the affected fiber tract demonstrates T2 and FLAIR hyperintensities. In the chronic phase the fiber tract will demonstrate atrophy, however, the T2 and FLAIR hyperintensities may persist for months after the initial inciting event.