UC San Diego

Epidural electrical stimulation (EES) has garnered interest as a treatment option for spinal cord injury and has promoted the recovery of autonomic and voluntary motor function in patients with paraplegia. While spatiotemporal EES has been optimized to facilitate functional movement, there remains an unmet need for targeted, spatially selective stimulation of the spinal cord. We employed a 156-channel, thin-film, conformal, and low-impedance Platinum Nanorod microelectrode array for focal EES of the rat lumbar spinal cord. We first investigated the neuroanatomy of the rat lumbar spinal cord through dissection and MRI to inform the size and implantation location of the microelectrode array. We tailored the shape of the electrode to promote conformity to the curvilinear surface of the spinal cord and implemented on-electrode ground contacts to facilitate the delivery of spatially controlled stimulation to the dorsal root entry zones. We characterized the capabilities of the final dorsal microelectrode array through an analysis of selective muscle recruitment. Lastly, we assessed the feasibility of high-density microelectrode arrays with circumferential and dorsolateral spinal cord coverage for activation of dorsal nerve roots running within the intrathecal space. In summary, our high-density, conformal microelectrode array provides the spatial resolution and conformity necessary to deliver focal stimulation to the rat lumbar spinal cord and selectively activate hindlimb muscles.