Spinal Cord Lower Urinary Tract Control in Humans

Background and Objective: Although there have been significant advancements in functional magnetic resonance imaging (fMRI) studies that have enhanced our understanding of brain control over bladder function in humans, a notable gap still exists in exploring spinal cord involvement in real-time. The objective of this study was to develop and validate an fMRI protocol to assess innate spinal cord activity in humans within regions associated with bladder function. Methods: Twenty healthy adult participants 9 men, 11 women underwent functional magnetic resonance imaging (fMRI) of the spinal cord during implementation of a natural bladder filling protocol and simulated bulbocavernosus reflex (sBCR). Anatomical images were obtained, followed by resting-state and task-based fMRI assessments during both full and empty bladder states. Functional spinal neuroimaging data were analyzed using a custom pipeline comprised of Spinal Cord Toolbox, FSL, and MATLAB scripts for preprocessing and analysis. Key Findings and Limitations: Our preliminary findings revealed activation in 15 participants (7 men, 8 women), exhibiting diverse patterns of activity across the T10-S5 neuronal segments during task-fMRI sessions conducted with both empty and full bladder conditions during sBCR. The identified activated regions included sympathetic (T10-L2), parasympathetic (S2–S4), and somatic nuclei (S2–S4), previously implicated in facilitating lower urinary tract (LUT) control. Notably, our preliminary findings suggest that sex differences may influence these activation patterns, though further investigation and second-level analysis are warranted to confirm this observation. Conclusions: Although preliminary, our findings demonstrate, for the first time, the efficacy of our fMRI protocol in detecting task-induced activity in the lumbosacral spinal cord, underscoring our capability to precisely target specific regions responsible for regulating LUT function.