Epidural electrical stimulation and hemodynamic control after spinal cord injury

Abstract

Spinal cord injury impairs cerebral autoregulation (i.e., the buffering of changes in blood pressure in an effort to maintain cerebral blood flow constant) and baroreflex sensitivity (i.e., the appropriate heart rate responses to changes in blood pressure), due in part to the disruption of supraspinal sympathetic control of circuits below the level of injury. This impairment is almost certainly associated with the greater risk of cerebrovascular and heart disease observed in this population.We have previously shown in people with spinal cord injury that epidural electrical stimulation of the spinal cord below the level of injury (eSTIM) activates disconnected sympathetic circuits. Furthermore, long‐term daily application of eSTIM can in some cases lead to plasticity that restores function, even when eSTIM is off. It is not clear if eSTIM activation of sympathetic circuits restores cerebral autoregulation and baroreflex function after spinal cord injury, or if functionally‐relevant plasticity occurs after long‐term application of eSTIM.Here, we show that activating eSTIM immediately improves cerebral autoregulation and baroreflex sensitivity. These positive immediate effects were repeatable over several months. Long‐term daily eSTIM for at least 12 weeks did not affect cerebral autoregulation or baroreflex function when stimulation was off, indicating that functionally‐relevant plasticity did not occur. In conclusion, immediate application of eSTIM may be a viable therapy for improving hemodynamic control after spinal cord injury.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada, Canadian Institutes of Health Research, Libin Cardiovascular Institute of Alberta, Hotchkiss Brain Institute, Compute Canada.Cerebral autoregulation was consistently improved with the activation of eSTIM as indicated by increased phase lag between blood pressure and cerebral blood flow. Cardiovagal baroreflex function was also improved as indicated by more rapid heart rate responses to changes in blood pressure. **indicates significant difference (p<0.005)Figure 1