Intraspinal Microstimulation of Dorsolateral Funiculus for Coordinated Bladder Control

Neurogenic lower urinary tract dysfunction (NLUTD) represents a common and severe complication following spinal cord injury (SCI), profoundly impacting the quality of life and contributing to significant morbidity through recurrent infections and renal complications. Current management strategies impose significant compromises, with clean intermittent catheterization (CIC) being burdensome and showing poor long-term adherence, while sacral anterior root stimulation (SARS) typically restores emptying but lacks sensory feedback. In this study, we explore whether targeted electrical microstimulation of ascending bladder afferent pathways within the lumbar dorsolateral funiculus (DLF) can recreate afferent signals of bladder fullness. Using custom-fabricated intraspinal microelectrode arrays, we characterized the spatiotemporal patterns of bladder-responsive neural activity in the L2-L4 spinal segments of anesthetized rats during controlled bladder filling cycles. Mapping experiments revealed highly localized neural responses within DLF that exhibited robust firing patterns associated with bladder filling. Furthermore, patterned electrical microstimulation delivered to DLF coordinates corresponding to filling-responsive zones successfully triggered coordinated voiding in 91.7% of trials, characterized by appropriate intravesical pressure increases and rhythmic external urethral sphincter (EUS) activity. The evoked responses demonstrated remarkable spatial specificity without concurrent hindlimb motor activation, as contrasted with spinothalamic tract (STT) stimulation. These findings identify DLF as a promising anatomical substrate for targeted electrical microstimulation and establish proof-of-concept for the sensory component of a future closed-loop neuroprosthetic system aimed at restoring bladder function following SCI.