1009 In-House Microelectrode Arrays Detect Urodynamic Changes in Spinal Cord Compound Action Potentials

INTRODUCTION: Neurogenic bladder dysfunction secondary to spinal cord injuries (SCI) significantly decreases quality of life and predisposes patients to severe sequelae, such as urinary tract infections and septicemia. Spinal cord-machine interface (SCMI) is a promising approach to restore bladder functions. In this study, we fabricated integrated planar microelectrode arrays (MEA) for the detection of axonal compound action potentials (CAPs). This enabled the recording of axonal signals corresponding to bladder filling and bladder volume, an essential component for the development of a bidirectional, closed loop bladder-control neuroprostheses. METHODS: We fabricated 16- and 32-channel MEA on a shank probe that was inserted into the dorsolateral white matter containing the ascending Lissauer's tract, of six female Sprague-Dawley rats via a T12-L1 laminectomy. Bladders were surgically catheterized and 0.9% normal saline was infused at a constant rate, held, emptied, and repeated for multiple trials. Firing rates were correlated with different bladder states. RESULTS: Distinct firing rate changes within the Lissauer tract were observed during bladder filling, holding and emptying states. We mostly observed axonal CAPs that were maximally active during filling or holding states, with reduction in firing rates during emptying. These CAP patterns could be repeatedly detected only via their specific channels, confirming the spatial specificity of our electrode interface. CONCLUSIONS: Bladder states are differentially encoded by specific regions in the Lissauer tract and coding varies between filling, holding and emptying phases. In decoding such axonal signals, MEA could serve as a viable means to detect the bladder states in patients with SCI. Additionally, this electrode interface can be more broadly applied for other applications of SCMI beyond restoration of bladder function.