A systematic review of cerebral hemodynamic responses to neural activation following stroke.

The aim of this study was to systematically review CBF studies, assess their methodological quality, and identify trends in the association between task-related brain activation patterns and CBF changes in ischemic stroke (IS) patients. We searched the MEDLINE, EMBASE, CINAHL, and Web of Sciences databases for studies of functional recovery with quantification of CBF responses to brain activation paradigms after IS. Titles, abstracts and full text of articles were scrutinised according to pre-defined selection criteria. Two independent reviewers (AS, VH) undertook the methodological quality screening and data extraction of the included studies. Sixteen of the 1,521 identified studies were relevant. Studies showed weaknesses in key methodological criteria (e.g. population size, discussion of limitations), and only seven studies compared responses with a control population. Overall, there was no agreement between CBF responses in either the affected or unaffected hemisphere and prediction of post-IS recovery. Some studies have shown a higher CBF increase in the unaffected hemisphere when the affected hemisphere was stimulated compared to the healthy control responses. However, CBF responses in the affected hemisphere were inconsistent. Many post-IS CBF studies are of poor methodological quality, and do not demonstrate a consistent response post-IS or a relationship with recovery. Further longitudinal studies assessing the natural history of CBF responses to brain paradigms following IS should be undertaken to determine prognostic significance, and to inform future therapeutic strategies.