Diffusion imaging in post-stroke plasticity: capacity and adequacy of visualization

Abstract

In recovery from stroke an essential mechanism is plasticity, in which changes in the strength of synaptic connections lead to functional or morphological reorganization. The methods that are commonly used to study post-stroke recovery in the brain predominantly measure brain function, indicating that activation patterns change. However, changing activation patterns do not necessarily reflect plasticity and plasticity is mainly determined by structural connectivity. With diffusion imaging (DI) structural connections can be visualized and quantified and it is suggested that DI is able to determine whether fiber reorganization accounts for changing activation patterns. The objective of the present review was to determine whether the relation between plasticity, DI and recovery is as straightforward as assumed. It is found that the relation between DI, plasticity and recovery is very complex. Changes in DI metrics do not necessarily reflect plasticity mechanisms and occurring plasticity does not always result in (beneficial) recovery changes. Nevertheless, DI is a valuable and necessary tool in investigating the occurrence of plasticity. By combining DI with functional techniques and outcome measures, structural changes can be coupled to changes in activation patterns, and by relating this to functional outcome, more understanding will be gained about the occurrence and significance of plasticity.