Pudendal Stimulation Research Articles

Characterization of bilateral, pudendal nerve-evoked, urethral rhabdosphincter contractions in anesthetized cats

Pudendal (PUD) efferent activity contracts urethral rhabdosphincters to resist urine leakage. This study evaluates the potential for PUD nerve stimulation to provide benefit for urinary incontinence. Acute responses of the urethral rhabdosphincter to modulation of current amplitude, pulse duration (PD), and frequency of stimulation were examined. Urethral pressure was measured using a microtip catheter in chloralose-anesthetized, male cats with or without acute spinalization at T10. Stimulation was applied from an external pulse generator coupled to cuff electrodes placed around left and right PUD nerves in the ischiorectal fossa, central to its branching. Bladder pressure clamp techniques were used for testing effects of stimulation on time and rate of leakage during PUD stimulation. Single pulses (0.1 ms) produced single transient increases in urethral pressure that peaked at 50 ms and diminished to 50% of peak at 90 ms. Threshold current was 88 ± 30μA with maximal responses occurring with 50% increases in current. Peak pressures increased with increasing PDs between 40–180μs. Summation, tetany, peak pressures, and fatigue of responses to increasing stimulation frequencies during 2 min periods of stimulation are described. Stimulation under pressures that are typical during bladder filling or during bladder contractions (30–40 cm H2O) prevented leakage up to an hour in some animals, increased the median time to leak from 0.3 min to 56.0 min, and decreased the median rate of leakage from 1.44 ml/min to 0.04 ml/min when leakage did occur in less than hour. During rapid elevations in bladder pressure to simulate a Valsalva-like bladder pressure (120 cm H2O), PUD stimulation increased the median time to leak from 9 s to 93 s and decreased the median rate of leakage from 5.5 ml/min to 3.4 ml/min. These results support future studies of bilateral PUD stimulation in a clinically-relevant, animal model of urinary incontinence.

Laparoscopic implantation of electrodes for bilateral neuromodulation of the pudendal nerves and S3 nerve roots for treating pelvic pain and voiding dysfunction.

The objective of this video is to describe the technique for laparoscopic implantation of electrodes for bilateral neuromodulation of S3 and pudendal nerves. We report a successful case of a 48-year-old woman with spina bifida occulta referred with a 14-year history of intense acyclic pelvic pain, urinary hesitancy, and intermittent flow refractory to various conservative measures. The procedure began with the removal of two previously placed InterStims. A quadripolar electrode was then laparoscopically inserted into Alcock's canal and attached to the pelvic pectineal line. Another lead was placed juxtaneurally to S3. Lead contacts were then exteriorized, and the peritoneum closed. The same procedure was then performed on the contralateral side. The leads were connected to a 16-pole rechargeable pulse generator. Postoperatively, the patient developed an acute dissection and partial thrombosis of the external iliac artery, which was treated endovascularly. Complete pain resolution was observed with simultaneous S3 and pudendal stimulation, with pudendal stimulation turned off for voiding. We conclude that laparoscopic implantation of neuromodulation electrodes allows simultaneous stimulation of S3 and pudendal nerves, providing more programming options and possibly increasing success rates in complex pelvic floor dysfunction cases.

Screening and Optimization of Nerve Targets and Parameters Reveals Inhibitory Effect of Pudendal Stimulation on Rat Bladder Hypersensitivity.

Neuromodulation has been reported to reliably improve symptoms of bladder overactivity and sometimes pain. The effect of electrical stimulation of several nerve pathways demonstrated to alter cystometric responses to bladder distension was examined on nociceptive responses in models of bladder hypersensitivity. Bladder hypersensitivity was produced by several published methods including neonatal inflammation, acute inflammation, and chronic stress. Effects of different sites of stimulation (L6 and T13 nerve roots, proximal and distal pudendal nerves [PNs]) on nociceptive reflex responses to urinary bladder distension in urethane-anesthetized female rats were assessed and a parametric analysis of parameters of stimulation was performed. Bilateral biphasic stimulation of the proximal PNs resulted in statistically significant inhibition of visceromotor and cardiovascular responses to bladder distension in rats made hypersensitive by neonatal bladder inflammation. We found a range of optimal stimulation frequencies (5-10 Hz) which produced robust inhibitory effects when using short pulse widths (100-240 μs). Onset of inhibition was within minutes and persisted for several minutes after the stimulus was discontinued. Use of bilateral PN stimulation in acute inflammation and stress-induced hypersensitivity models as well as unilateral stimulation, very distal PN cutaneous branch stimulation, and stimulation of the T13 and L6 nerve roots all proved ineffective with the parameters used. This study suggests that inhibitory effects of bilateral PN stimulation can be evoked in a rodent hypersensitivity model at relatively low frequencies with short pulse widths. The onset of effect is rapid, which suggests the potential for treating episodic pain in painful bladder disorders.

Stimulation of the Neurovascular Bundle Results in Rhabdosphincter Contraction in a Proportion of Men Undergoing Radical Prostatectomy

To use nerve conduction studies to clarify the functional innervation of the male urethral rhabdosphincter (RS). In particular, to test the hypothesis that in some men, fibers of the neurovascular bundle supply the RS. These fibers may be at risk during radical prostatectomy. Men undergoing robot-assisted radical prostatectomy for clinically localized prostate cancer were included. Men with a history of pelvic surgery and/or radiation and/or trauma, obesity, or neurological diseases were excluded. Nerve conduction studies were performed before and after prostate removal. The St. Mark's pudendal electrode was used for pudendal (control) stimulation. The ProPep Nerve-Monitoring System (ProPep Surgical, Austin, TX) was used to stimulate the neurovascular bundle at the level of the prostate base, mid, and apex. ProPep needle electrodes inserted into the RS were used to measure evoked compound motor action potential response. Results were only included if a valid pudendal control was elicited. Seventeen men in total underwent investigation. Valid measurements were obtained after initial quality control in seven. In two cases, evidence of sphincteric activation was observed, providing evidence to support neurovascular bundle innervation of the RS. In the other five patients, no intrapelvic nerve supply was demonstrated. Somatic nerve supply to the RS is variable. Direct intrapelvic supply to the RS may exist in some men. This may be one explanation as to why some patients unexpectedly develop severe urinary incontinence postoperatively despite technically satisfactory surgery. Further research is required to validate our findings.

Effects of pudendal neuromodulation on bladder function in chronic spinal cord-injured rats

Few studies have investigated the feasibility of using pudendal neuromodulation to regulate bladder function in spinal cord-injured (SCI) animals. The present study aimed to determine the effects of electrical activation of the pudendal sensory branch on improving voiding functions in rats 6 weeks after a spinal cord injury and to explore the underlying neuromodulatory mechanisms. Two urodynamic measurements were used to assess the effects of electrical stimulation (ES) on bladder and urethral functions: simultaneous recordings of the intravesical pressure (IVP) during continuous isotonic transvesical infusion (i.e., isotonic IVP) and external urethral sphincter (EUS) electromyography (EUS-EMG), and simultaneous recordings of transvesical pressure under isovolumetric conditions (i.e., isovolumetric IVP) and urethral perfusion pressure (UPP). Six weeks after the SCI, the rats showed voiding dysfunction, as indicated by abnormal cystometric measurements (e.g., increased volume threshold, increased contraction amplitude, and increased residual volume, and decreased voided volume). The voiding efficiency (VE) decreased to 13% after the SCI, but increased to 22-34% after applying pudendal afferent stimulation. In addition, pudendal stimulation significantly increased the EUS burst period and increased the difference between the UPP and the high-frequency oscillation (HFO) baselines, and changed the time offset between bladder and EUS activities. These findings suggest that pudendal afferent stimulation improved the VE by prolonging the micturition interval, decreased the urethral resistance, and recovered detrusor-sphincter dyssynergia during the voiding phase. This study demonstrates the feasibility of using pudendal neuromodulation in chronic SCI rats. These results could aid in developing an advanced neural prosthesis to restore bladder function in clinical settings.

Restoration from acute urinary dysfunction using Utah electrode arrays implanted into the feline pudendal nerve.

To investigate intrafascicular pudendal nerve stimulation in felines as a means to restore urinary function in acute models of urinary incontinence, overactive bladder, and underactive bladder. Felines were anesthetized, and high-electrode-count (48 electrodes; 25 electrodes/mm(2) ) electrode arrays were implanted intrafascicularly into the pudendal nerve trunk. Electrodes were mapped for their ability to selectively or nonselectively excite the external anal sphincter, external urethral sphincter, and the detrusor bladder muscle. Statistical analysis was carried out to quantify reflexive voiding efficiencies, mean impedances of the microelectrodes used in this study, and to determine what differences, if any, in bladder contraction amplitudes were evoked by different electrode configurations. Multielectrode arrays implanted into the pudendal nerve trunk were able to selectively and nonselectively excite genitourinary muscles. After inducing urinary incontinence with bilateral pudendal nerve transections (proximal to the implants), electrical stimulation delivered through certain microelectrodes was able to significantly reduce leaking (p = 0.008). Electrical stimulation delivered through detrusor selective electrodes was able to inhibit reflexive bladder contractions and excite bladder contractions, depending on the stimulation frequency. Specific electrode configurations were able to drive significantly (p < 0.001) larger bladder contractions than other electrode configurations, depending on the preparation. Successful reflexively or electrically driven bladder contractions were achieved in 46% and 38% of the preparations, respectively, an observation that has not been noted in previously published feline pudendal stimulation studies. Multielectrode arrays implanted intrafascicularly into the pudendal nerve trunk may provide a promising new clinical neuromodulation therapy for the restoration of urinary function.

Effects of pudendal nerve stimulation with different frequency on bladder dysfunction in spinal cord injury dogs

Objective To determine the effects of pudendal ncrve stimulation with different frequency(5 Hz,20 Hz) on bladder dysfunction dogs after spinal cord injury.Methods The study was done in 4 dogs which chronic spinal cord transection at T9-T10 level.All the dogs underwent electrical stimulation of pudendal nerve (5 Hz,20 Hz).Then,bladder capacity,compliance,non-voiding contraction number (NVC) and voiding efficiency before and during stimulation were compared.Results The bladder capacity and the compliance was increased ( 58.9 ± 17.4) ％ and (53.1 ± 4.9 ) ％ ( P ＜ 0.05 ) by pudendal nerve stimulation with low frequency (5 Hz).Detrusor overactivity can be inhibited and the NVC decreased from 1.7 ± 1.3 to 0.9 ± 1.1.Pudendal nerve stimulation with medium frequency ( 20 Hz) can induce bladder contraction and increased voiding efficiency from (5.8 ± 1.0) ％ to ( 16.3 ± 2.6 ) ％ ( P ＜0.05).Conclusions Pudendal nerve stimulation with low frequency can inhibit detrusor overactivity and increase the bladder capacity and compliance in spinal cord injury dogs.Pudendal nerve stimulation with medium frequency can induce bladder contraction and increased voiding efficicncy. Key words: Bladder; Spinal cord injury; Pudendal nerve stimulation; Dogs; Urodynamics

Sacral Neuromodulation with an Implantable Pulse Generator in Children with Lower Urinary Tract Symptoms: 15-Year Experience

Sacral nerve modulation with an implantable pulse generator is not an established treatment in children. This therapy has been described for dysfunctional elimination syndrome and neurogenic bladder. We report 2 new indications for this approach in children, ie bladder overactivity and Fowler syndrome. The aim of this study was to improve the results of future treatment for sacral neuromodulation in children by describing factors favorable for good outcomes with this method. A total of 18 children 9 to 17 years old were studied. Mean ± SD followup was 28.8 ± 43.8 months. Of the patients 16 underwent S3 sacral neuromodulation and 7 underwent pudendal stimulation (5 as a revision, 2 from the beginning). Initial full response was achieved in 9 of 18 patients (50%) and partial response in 5 (28%). In patients presenting with incontinence mean ± SD number of incontinence episodes weekly improved significantly from 23.2 ± 12.4 to 1.3 ± 2.63 (p <0.05). In patients requiring clean intermittent catheterization there was a significant decrease in mean ± SD daily frequency of catheterization from 5.2 ± 1.6 to 2.0 ± 1.9 (p <0.05). At the end of the study 6 of 15 patients (40%) had a full response and 5 (33%) had a partial response, while 4 implantable pulse generator devices (27%) were explanted because of failure. Sacral neuromodulation is feasible in the pediatric population, with good short-term (78% full or partial response) and satisfactory long-term results (73%). Sacral neuromodulation can offer good results for overactive bladder, dysfunctional elimination syndrome and Fowler syndrome. Pudendal nerve stimulation is a feasible salvage treatment that can be useful in cases when S3 implantation is impossible or unsuccessful.

New strategies of pelvic nerves stimulation for recovery of pelvic visceral functions and locomotion in paraplegics

To present new strategies of pelvic nerves stimulation to enhance micturition, to control spasticity, and to recover locomotion in paraplegics. Three consecutive patients-Th5, Th7, and Th10 spinal cord injured-underwent laparoscopic transperitoneal implantation of octipolar electrodes to the sciatic and the pudendal nerves and one double extradural Brindley-Finetech electrode bilaterally to the sacral nerve roots S3 and S4. The two octipolar electrodes were connected to an implanted rechargeable generator, while the double Brindley electrode was connected to an implanted Brindley-Finetech receiver block. Continuous stimulation of the sciatic and pudendal nerves at a frequency of 20 Hz in all three patients permits complete control of the spasticity of the lower extremities and of reflex incontinence. Bladder emptying is obtained by sacral nerve roots stimulation alone in the first patient, by simple interruption of pudendal stimulation in the second ("pudendal-deblockade") and by simultaneous sacral nerve roots stimulation with high-frequency pudendal nerve blockade in the third patient. Functional electrical stimulation of the femoral nerves enables the Th4 paraplegics lower-limb cycling and the two further patients standing and alternative locomotion. This short series indicated that laparoscopic implantation of neuroprothesis to the pelvic nerves offers absolutely new strategies based on new combinations of various reported methods to enhance bladder functions and to recover some locomotion in paraplegics.

Chronic pudendal neuromodulation: Expanding available treatment options for refractory urologic symptoms

Chronic pudendal nerve stimulation (CPNS) is a logical alternative particularly in those who fail sacral stimulation. We evaluated symptoms, complications, and satisfaction after CPNS. We retrospectively reviewed patients having a tined lead placed at the pudendal nerve via the ischial-rectal approach. Demographics, history, complications, and pre-implant voiding diary data were collected. In those responding to CPNS, post-implant symptom changes were measured with the Interstitial Cystitis Symptom and Problem indices (ICSI-PI) and voiding diaries at 3, 6, and 12 months, and a mailed survey. The majority of 84 patients (78.6% female; age 51.8 ± 16.9 years) had interstitial cystitis/painful bladder syndrome, or overactive bladder. Pudendal response (≥ 50% improvement) occurred in 60/84 (71.4%), however 5 of these chose sacral neuromodulation. Almost all (93.2%) who had previously failed sacral neuromodulation responded to pudendal stimulation. Outcomes were evaluated in 55 continuing on CPNS (median follow up 24.1 months). Seven complications requiring 5 revisions, and 4 other re-operations occurred. Five were explanted. Over time, significant improvements in frequency (P < 0.0001), voided volume (P < 0.0001), incontinence (P < 0.0001), and urgency (P = 0.0019) occurred. ICSI-PI scores significantly improved over 12 months (P < 0.0001). Survey responses indicated that most still had a device (35/40; 87.5%) continuously in use (24/29; 82.8%), and overall bladder, pelvic pain, incontinence, urgency, and frequency symptoms had improved. CPNS is a reasonable alternative in complex patients refractory to other therapies including sacral neuromodulation. Continued research is needed to fully assess long-term outcomes and identify predictors of success.

Potential Use of Pudendal Nerve Stimulation for Voiding Dysfunction

Voiding dysfunction—including urinary urgency, urinary frequency, urge incontinence, and nonobstructed urinary retention—and neurogenic bladder are common diagnoses that can be difficult to treat. Neuromodulation is typically reserved for patients who are intolerant or refractory to medication. Sacral nerve stimulation has been used successfully to treat voiding dysfunction and has a long record of safety and efficacy. Pudendal nerve stimulation is emerging as another option in the treatment of voiding dysfunction. Recent reports have shown that pudendal nerve stimulation is at least as effective as sacral nerve stimulation and works in some instances in which sacral stimulation has failed. Furthermore, in a direct comparison, patients chose pudendal stimulation as a superior option.

Influence of naloxone on inhibitory pudendal-to-bladder reflex in cats

To determine the involvement of opioid receptors in the inhibitory pudendal-to-bladder reflex, the effect of naloxone (0.01–1 mg/kg, i.v.), an opioid receptor antagonist, on the inhibition of bladder activity evoked by pudendal nerve stimulation was investigated in α-chloralose anesthetized cats. The inhibition of reflex isovolumetric bladder contractions induced by pudendal nerve stimulation (5–10 Hz) at intensity threshold (T) for producing complete inhibition was significantly suppressed by naloxone at a high dose (0.3 mg/kg). However, the inhibition elicited at higher intensities (1.5–3 T) was not changed. Naloxone (1 mg/kg) did not alter the frequency dependence of the inhibitory effect of pudendal stimulation. During cystometrograms (CMGs) pudendal nerve stimulation significantly increased bladder capacity to 155.1 ± 24.5% and 163.4 ± 10% of the control at stimulation intensities of 1 T and 1.5–3 T, respectively. After administration of naloxone (1 mg/kg), the bladder capacity during pudendal nerve stimulation at inhibition threshold (1 T) was not significantly different from control, but it was significantly increased at higher intensities (1.5–3 T). Naloxone alone markedly reduced bladder capacity to 43 ± 11.1% of the control, and pudendal stimulation completely reversed this facilitatory effect. This study revealed that activation of opioid receptors contributes to or facilitates the inhibitory pudendal-to-bladder reflex. The reduction in bladder capacity after naloxone treatment also indicates that endogenous opioid peptides mediate a tonic inhibition of micturition. Understanding the neurotransmitter mechanisms involved in the inhibitory pudendal-to-bladder reflex could promote the development of new treatments for bladder overactivity and incontinence.

Cortical substrate of bladder control in SCI and the effect of peripheral pudendal stimulation

We investigated (i) the central representation of lower urinary tract (LUT) control and (ii–iii) the acute and short-term central neuromodulatory effect of peripheral pudendal nerve stimulation in incomplete spinal cord injured (SCI) patients using functional magnetic resonance imaging (fMRI). The urinary bladder of eight SCI patients has been passively filled and emptied using a catheter, to identify the neural substrate of bladder control (i), and with simultaneous peripheral pudendal nerve stimulation to investigate its acute central neuromodulatory effect (ii). To identify the potential effects of pudendal nerve stimulation treatment (iii), six patients underwent a 2-week training using pudendal nerve stimulation followed by another fMRI session of bladder filling. The pre- and post-training fMRI results have been compared and correlated with the patient's pre- and post-training urological status. Our results suggest that the central representation of bladder filling sensation is preserved in the subacute stage of incomplete SCI. However, compared to earlier data from healthy subjects, it shows decreased neural response in right prefrontal areas and increased in left prefrontal regions, indicating diminished inhibitory micturition control as well as, compensatory or decompensatory reorganization of bladder control. We also provide evidence for a neuromodulatory effect of acute pudendal nerve stimulation, which was most prominent in the right posterior insula, a brain region implicated in homeostatic interoception in human. Pudendal stimulation training also induced significant neuromodulation, predominantly signal increases, in the normal cortical network of bladder control. Correlations with the patient's urological status indicate that this neuromodulatory effect may reflect the clinical improvement following training.

Functional Impact of the Rhabdosphincter Branch of the Pelvic Nerve on the Membranous Urethra in Comparison to That of the Pudendal Nerve in Male Rabbits

Introduction: The innervation of the membranous urethra (MU) is still under debate. We analysed the functional effects of electrostimulation of the rhabdosphincter branch of the pelvic nerve (RBP) on the MU in a standardized male rabbit model, paying attention both to the efferent and the possible afferent effects of stimulation. Material and Methods: Six male rabbits (chinchilla bastards) were included in this study. Pudendal nerve branches as well as pelvic nerve branches were exposed bilaterally in all animals. Randomized electrostimulation trials of both the pudendal nerve fibres and the RBP were carried out using a biphasic signal (0.3 mA, 200 μs). The stimulation frequency ranged from 10 to 40 Hz in a randomized pattern. Changes in MU pressure were measured urodynamically. The pressure changes occurring as a result of stimulation were compared in both nerve structures. At the end of the stimulation trial, the RBP and the pudendal nerve were dissected at different positions before repeating the stimulation and the MU pressure recording. Results: The mean MU baseline pressure without stimulation was 24 cm H₂O (range 21–27) in all animals. During unilateral pudendal stimulation, the mean pressure response rose by highly significant values (p < 0.005) compared to baseline. The pressure response was frequency dependent. Stimulation of the RBP resulted in a small but significant change of the MU pressure in the lower frequency range (10 and 20 Hz) (p > 0.05). On performing stimulation at higher frequencies, there was no significant difference from baseline. The pressure response of the MU during stimulation of the intact RBP did not differ significantly from the response after dissection of the RBP. However, after dissecting the pudendal nerve, the MU pressure response to RBP stimulation was diminished. Conclusion: Our results confirm the primacy of the pudendal nerve in the innervation of the MU. Stimulation of the RBP, however, may produce an afferent signal which is transmitted to the pudendal nerve, thus resulting in a pressure increase of the MU and contributing towards continence. We showed the importance of the RBP to maintain full urinary continence in rabbits. Our results suggest that substantially higher continence rates can be achieved through a nerve-sparing procedure in radical prostatectomy. Nerve-sparing radical prostatectomy incidentally also protects the RBP from injury.

Cortical Evoked Potentials in Subjects with True Premature Ejaculation/Im Kortex hervorgerufene Potentiale bei Patienten mit echter vorzeitiger Ejakulation

Cortical somato-sensory evoked potentials (SEPs) from pudendal stimulation were determined in 23 patients with true premature ejaculation (TPE) and in 25 subjects as a control group. SEPs give a cortical representation of the sensory stimuli arising from the genital area. The amplitudes of the evoked response in the cortical area (P1-N1-P2 wave) were 4.96 +/- 1.89 microV in subjects with TPE and 3.79 - 1.38 microV in the controls (means +/- SD). This difference is statistically significative (P less than 0.005). Our results show a greater cortical representation of the sensory stimuli from the genital area and suggest an organic basis for TPE.

Impact of Electrostimulation of Neurovascular Bundles and Pudendal Nerves on the Membranous Urethra in Male Rabbits

The pathophysiology of post-prostatectomy incontinence is supposed to be multifactorial. The impact of the neurovascular bundles on sphincter function is still under debate. We clarified the impact of cavernous nerves function on the MU. We compared MU pressure responses in male rabbits following electrophysiological stimulation trials on the neurovascular bundles vs pudendal nerve stimulation. Six male Chinchilla Bastard rabbits were included in this study. Pudendal and cavernous nerve branches were exposed bilaterally in all animals. Randomized electrostimulation of pudendal nerve fibers and the cavernous nerves, as confirmed by erection,) were done using a biphasic signal form of 0.3 mA for 200 microseconds. Stimulation frequency was changed in a randomized pattern from 10 to 40 Hz. Changes in MU pressure were measured urodynamically via a transurethral microtip catheter placed in the MU. Stimulation responses of the 2 nerve structures were compared. Mean baseline pressure in the MU without stimulation was 23 cm H(2)O (range 20 to 25) in all animals. During unilateral pudendal stimulation the mean pressure response increased highly significantly to 33, 43, 59 and 60 cm H(2)O at 10, 20, 30 and 40 Hz, respectively (p <0.005). In contrast, compared to baseline pressure cavernous nerve stimulation did not result in any significant changes in proximal urethral pressure (mean 23 cm H(2)O, range 20 to 25, p >0.05). Our results confirm the primacy of the pudendal nerve in the external urethral sphincter innervation. In contrast, stimulation of the cavernous nerves did not produce any pressure changes in the MU. These results confirm that the neurovascular bundles have no functional impact on the MU.

Sacral versus pudendal nerve stimulation for voiding dysfunction: A prospective, single‐blinded, randomized, crossover trial

The objective of the study was to compare sacral nerve stimulation (SNS) to pudendal nerve stimulation (PNS) for voiding dysfunction. Thirty subjects with voiding dysfunction had a tined lead placed at S3 and a second electrode implanted at the pudendal nerve via a posterior approach. In a blinded, randomized fashion, each lead was tested for 7 days. Voiding diaries and questionnaires were completed and outcomes monitored. The time to place a sacral lead was 25.85 min, pudendal lead 23.71 min (P = 0.57). Twenty-four of 30 (80%) subjects responded and had a permanent implant placed. PNS was chosen as a superior lead in 79.2%, SNS was superior in 20.8%. The order in which the lead was simulated had no impact on the final lead implanted and no carry over effect was seen. Overall reduction in symptoms was 63% for PNS and 46% for SNS (P = 0.02). On a 7-point scale from markedly worse to markedly better, the pudendal lead was superior to sacral for pelvic pain (P = 0.024), urgency (P = 0.005), frequency (P = 0.007), and bowel function (P = 0.049). Complications were minimal. This is the first blinded study of sacral versus pudendal stimulation for voiding dysfunction. Successful implantation of a pudendal lead was achieved in all subjects. The majority of subjects chose PNS to be superior to SNS. More patients and longer term data is needed to confirm these promising results.

Conditioning stimulus can influence an external urethral sphincter contraction evoked by a magnetic stimulation

To study the effect of a conditioning stimulus on an external urethral sphincter (EUS)contraction evoked by a magnetic stimulation at different time intervals. Seven healthy male volunteers underwent EUS pressure measurement. At baseline, magnetic stimulation of the lumbosacral spinal cord above the motor threshold was performed and evoked EUS pressure responses were recorded. The lumbosacral magnetic stimulation was repeated with same intensity, while a selective electrical dorsal penile nerve stimulation below the bulbocavernosus reflex (BCR) threshold was preceding at five different intervals (10, 20, 30, 50, 100 msec). The protocol was performed with empty and full bladder (BLA), and baseline responses were statistically compared to those with combined stimulation. When the dorsal penile nerve electrical stimulation preceded the lumbosacral magnetic stimulation by 20 msec (P=0.0048), 50 msec (P=0.0039), or 100 msec (P=0.0002), the amplitudes of the EUS pressure response with empty BLA were significantly reduced compared to lumbosacral magnetic stimulation alone. With a filled BLA, the amplitudes of the EUS were significantly reduced only at an interval of 50 msec (P<0.0001). A conditional sensory pudendal stimulation seems to have the capacity to inhibit the external urethral sphincter contraction induced by a magnetic stimulation. The inhibitory effect seems to depend on the latency between the peripheral and lumbosacral stimulation as well as on the degree of BLA filling. It remains to be proved if the neuromodulative effect of the conditional stimulus occurs at a spinal or supraspinal level.