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BMC Urology  2010 

Finite element modeling and in vivo analysis of electrode configurations for selective stimulation of pudendal afferent fibers

DOI: 10.1186/1471-2490-10-11

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Abstract:

A finite element model (FEM) of the male cat urethra and surrounding structures was generated to simulate IES with a variety of electrode configurations and locations. The activating functions (AFs) along pudendal afferent branches innervating the cat urethra were determined. Additionally, the thresholds for activation of pudendal afferent branches were measured in α-chloralose anesthetized cats.Maximum AFs evoked by intraurethral stimulation in the FEM and in vivo threshold intensities were dependent on stimulation location and electrode configuration.A ring electrode configuration is ideal for IES. Stimulation near the urethral meatus or prostate can activate the pudendal afferent fibers at the lowest intensities, and allowed selective activation of the dorsal penile nerve or cranial sensory nerve, respectively. Electrode location was a more important factor than electrode configuration for determining stimulation threshold intensity and nerve selectivity.Pudendal nerve stimulation is a potential means of restoring bladder function to persons with spinal cord injury (SCI). Stimulation of sensory (afferent) fibers either in the dorsal penile branch (DNP) or the cranial sensory branch (CSN) of the pudendal nerve can evoke stimulation frequency-dependent contraction or relaxation of the urinary bladder in cats [1,2]. However, the existence of comparable reflexes in persons with SCI remains unclear. In both experimental and clinical settings, intraurethral electrical stimulation (IES) has been utilized as a minimally invasive method to investigate these reflexes. However, the activation of multiple nerve pathways (pudendal and pelvic) by this approach did not enable identification of the specific sensory nerves responsible for the evoked bladder reflexes. The present study used a finite element model (FEM) and parallel in vivo measurements in the male cat to quantify the effects of electrode configuration and position on intraurethral activation of pudendal afferent n

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