The advent of diffusion tensor imaging (DTI)–MRI allows direct in vivo visualisation of white matter fibre tracts, opening a window on the important issue of functional connectivity in normal human brain. Furthermore, it provides a tool for measurement of fibre tract integrity in diseases of the central nervous system. Thus it is becoming possible to assess in a single patient whether specific fibre tracts will escape damage and also to relate these changes to clinical outcome. In particular, the application of DTI to the study of retrograde/anterograde degeneration of white matter pathways secondary to focal ischaemia may provide new insights into the mechanisms implicated in loss as well as recovery of function after stroke.

In this issue, two articles have applied DTI to investigate the time course and clinical correlates of secondary degeneration after subcortical stroke involving the motor pathway in patients who were prospectively studied over 3 months (within 1 week, 4 weeks and 12 weeks after stroke). To date, few data were available …