Enhanced Motor Recovery after Stroke with Combined Cortical Stimulation and Rehabilitative Training Is Dependent on Infarct Location

Background. Cortical electrical stimulation of the motor cortex in combination with rehabilitative training (CS/RT) has been shown to enhance motor recovery in animal models of focal cortical stroke, yet in clinical trials, the effects are much less robust. The variability of stroke location in human patient populations that include both cortical and subcortical brain regions may contribute to the failure to find consistent effects clinically. Objective. This study sought to determine whether infarct location influences the enhanced motor recovery previously observed in response to CS/RT. The efficacy of CS/RT to promote improvements in motor function was examined in 2 different rat models of stroke that varied the amount and location of cortical and subcortical damage. Methods. Ischemic infarctions were induced by injecting the vasoconstricting peptide endothelin-1 either (1) onto the middle cerebral artery (MCA) producing damage to the frontal cortex and lateral striatum or (2) into a subcortical region producing damage to the posterior thalamus and internal capsule (subcortical capsular ischemic injury [SCII]). Daily CS/RT or RT alone was then given for 20 days, during which time performance on a skilled reaching task was assessed. Results. Animals with MCA occlusion infarctions exhibited enhanced improvements on a skilled reaching task in response to CS/RT relative to RT alone. No such enhancement was observed in animals with SCII infarctions across the 20 days of treatment. Conclusions. The efficacy of CS for enhancing motor recovery after stroke may depend in part on the extent and location of the ischemic infarct.