There is growing evidence that electrical and magnetic brain stimulation can improve motor function and motor learning following brain damage. Rodent and primate studies have strongly demonstrated that combining cortical stimulation (CS) with skilled motor rehabilitative training enhances functional motor recovery following stroke. Brain stimulation following traumatic brain injury (TBI) is less well studied, but early pre-clinical and human pilot studies suggest that it is a promising treatment for TBI-induced motor impairments as well. This review will first discuss the evidence supporting brain stimulation efficacy derived from the stroke research field as proof of principle and then will review the few studies exploring neuromodulation in experimental TBI studies.

Background Electrical and magnetic brain stimulation can improve motor function following stroke in humans, rats and non-human primates, especially when paired with rehabilitative training (RT). Previously, we found in rodent stroke models that epidural electrical cortical stimulation (CS) of the ipsilesional motor cortex (MC) combined with motor rehabilitative training enhances motor function and motor cortical plasticity. It was unknown whether CS following experimental traumatic brain injury (TBI) would have similar effects. Objective To test the effects of CS combined with motor training after moderate/severe TBI on behavioral outcome and motor cortical organization. Methods Following unilateral controlled cortical impact (CCI) over the caudal forelimb area (CFA) of MC in adult male rats, forelimb reach training was administered daily over 9 weeks concurrently with sub-threshold 100Hz monopolar CS or no-stimulation control procedures. The rate and magnitude of behavioral improvements and changes in forelimb movement representations in the injured MC as revealed by intracortical microstimulation (ICMS) were measured. Results CCI resulted in severe motor impairments persisting throughout the 9 weeks of training in both groups, but CS treated animals had significantly greater behavioral improvements. CS also increased wrist motor cortical representation, one of the main movements used in the training task, compared to RT alone. However, the overall recovery level was modest, leaving animals still extremely impaired. Conclusions These data suggest that CS may be useful for improving rehabilitation efficacy after TBI but also raise the possibility that the CS parameters that are highly effective following stroke are suboptimal after moderate/severe TBI.