Introduction: Neurogenic bladder dysfunction is a debilitating sequela of various neurological disorders. Our understanding of the brain circuits involved in micturition has grown immensely over the past decade. Yet, assessing the functional attributes of spinal cord in relation to bladder function has proven to be a challenge. This study sought to utilize a novel neuroimaging modality, functional ultrasound imaging (fUSI), to characterize the spinal cord hemodynamics in response to micturition in rats. Methods: After inducing anesthesia with urethane, 12-14 week-old female Sprague-Dawley rats underwent multi-level laminectomy at T12-L1 to expose the lumbosacral spinal cord for fUSI recording. A transducer was inserted and secured to the bladder dome to record the pressure dynamics. A catheter connected to an infusion pump was inserted in the same location to fill the bladder with saline at constant rates of 0.1 and 0.2 ml/min. The fUSI recording was performed in sagittal and transverse planes and bladder pressure was recorded simultaneously. The dynamic changes in bladder pressure during the filling and voiding states were correlated to the power Doppler signal to illustrate the functional-anatomical correlates of micturition in spinal cord. Results: The bladder filling induced region-specific signal changes in spinal cord that were correlated with the temporal bladder pressure dynamics. The statistical parametric maps and event-related-average curves revealed region-specific changes in spinal cord hemodynamics that corresponded to bladder pressure during filling and voiding states. Spinal cord regions that yielded a significant hemodynamic response during the filling and voiding events were determined. Conclusions: Robust methods for assessment of spinal cord function in relation to micturition were lacking prior to this study. We employed a novel urodynamic-functional imaging model to illustrate the changes in fUSI signal in response to bladder filling and voiding, which revealed the spatiotemporal correlations between the spinal cord hemodynamics and micturition. The present model enables functional imaging of the spinal cord during voiding, and simultaneously captures multiple spinal cord levels across the sagittal plane. fUSI offers unique insights into the neural correlates of bladder function within the spinal cord, bridging a current gap in neuro-urology. SOURCE OF Funding: N/A
