In this issue, two original articles from highly experienced groups report on the use of diffusion tensor imaging (DTI) to map the dynamics of secondary degeneration after stroke (see pp 200–5 and 266–8). Thomalla et al¹ monitored in two patients the time course of Wallerian degeneration (WD) of the pyramidal tract following striatocapsular stroke. DTI was obtained on three occasions from the subacute into the chronic stage. They found a progressive decrease of the fractional anisotropy (FA) with an increase in mean diffusivity (MD) in the pyramidal tract at the level of the cerebral peduncle, reflecting the changes expected in WD—a progressive disintegration of fibre structure. Hervé et al² serially studied nine patients from 1 week to 6 months following MCA territory stroke, focusing on the ipsilateral thalamus. They found significant increases …