Principles Underlying Post-Stroke Recovery of Upper Extremity Sensorimotor Function – A Neuroimaging Perspective

Book excerpt: Neuroimaging post-stroke has the potential to uncover underlying principles of disordered function and recovery characterizing defined patient groups, including their long term course as well as individual variations. (MRI) measuring task related activation as well as resting state. Functional MRI can be performed by MRI to detect blood flow and associated changes in brain function. For structural MRI robust and accurate computational anatomical methods like voxel-based morphometry and surface based techniques are available. The investigation of the connectivity between brain regions and disruption after stroke is facilitated by diffusion tensor imaging (DTI). Intra- and interhemispheric coherence may be studied by the use of the techniques of electroencephalography and transcranial magnetic stimulation. Consecutive phases of stroke recovery (acute, subacute, early chronic and late chronic stages) are each distinguished by intrinsic processes. The site and size of lesions entail partially different functional implications. New strategies to establish a specific function of a lesion site. Large-scale lesions often imply poor cerebral blood flow which impedes recovery significantly and possibly interferes with BOLD response of functional MRI. Thus, depending on the site and size of the infarct, the patterns of recovery will vary. These include, in the perilesional area, intrinsic compensatory mechanisms using alternative cortical and subcortical pathways, or behavioral compensatory strategies, eg by using the non-affected limb. In this context, behavioral and neuroimaging measures should be developed and applied to delineate aspects of learning during recovery. Of special interest in the recovery of hand paresis is the interplay between sensory and motor areas in the posterior parietal cortex. The dominant disability should be, from the level of elementary to hierarchically higher processes, such as neglect, apraxia, and motor planning. In summary, this research covers new trends in state of the art neuroimaging of stroke during recovery from upper limb paresis. Integration of behavioral and neuroimaging findings in probabilistic brain atlases.