Motor cortex stimulation does not lead to functional recovery after experimental cortical injury in rats

Background: Motor impairments are among the major complications that develop after cortical damage caused by either stroke or traumatic brain injury. Motor cortex stimulation (MCS) can improve motor functions in animal models of stroke by inducing neuroplasticity. Objective: In the current study, the therapeutic effect of chronic MCS was assessed in a rat model of severe cortical damage. Methods: A controlled cortical impact (CCI) was applied to the forelimb area of the motor cortex followed by implantation of a flat electrode covering the lesioned area. Forelimb function was assessed using the Montoya staircase test and the cylinder test before and after a period of chronic MCS. Furthermore, the effect of MCS on tissue metabolism and lesion size was measured using [F-18]-fluorodesoxyglucose (FDG) mu PET scanning. Results: CCI caused a considerable lesion at the level of the motor cortex and dorsal striatum together with a long-lasting behavioral phenotype of forelimb impairment. However, MCS applied to the CCI lesion did not lead to any improvement in limb functioning when compared to non-stimulated control rats. Also, MCS neither changed lesion size nor distribution of FDG. Conclusion: The use of MCS as a standalone treatment did not improve motor impairments in a rat model of severe cortical damage using our specific treatment modalities.