Stroke recovery enhancing therapies: lessons from recent clinical trials

Poststroke recovery processes include restoration or compensation of function, respectively functions initially lost or new functions acquired after an injury. Therapeutic interventions can enhance these processes and/or reduce processes impeding regeneration. Numerous experimental studies suggest great opportunities for such treatments, but the results from recent large clinical trials using neuromodulators such as dopamine and fluoxetine are disappointing. The reasons for this are manifold affecting forward translation of results from animals models into the human situation. This "translational road block" is defined by differences between animals and humans with regard to the genetic and epigenetic background, size and anatomy of the brain, cerebral vascular anatomy, immune system, as well as clinical function and behavior. Backward blockade includes the incompatible adaption of targets and outcomes in clinical trials with regard to prior preclinical findings. For example, the design of clinical recovery trials varies widely and was characterized by the selection of different clinical endpoints, the inclusion a broad spectrum of stroke subtypes and clinical syndromes as well as different time windows for treatment initiation after infarct onset. This review will discuss these aspects based on the results of the recent stroke recovery trials with the goal to contribute to the currently biggest unmet need in stroke research - the development of a recovery enhancing therapy that improves the functional outcome of a chronic stroke patient.