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Purpose: Prior to implantation of a chronic sacral neurostimulator, it is important to establish which patients might profit from this kind of therapy in order to ensure, by means of a PNE (peripheral nerve evaluation) test, that the implantation of a permanent stimulating device is effective. In this study we compared the two different techniques used in our department (implantation of the permanent neurostimulation electrodes, the so-called "two-stage-implantation" vs. conventional PNE)., Materials and Methods: We performed a sacral nerve stimulation in 53 patients (mean age: 49.7 years, range: 14 - 75 years) over a minimum of 5 days. In 42 patients we performed a conventional PNE, 11 patients underwent "two-stage implantation" with implantation of the permanent electrodes., Results: 52 of 53 patients received bilateral test stimulation (9 % at S2, 91 % at S3). One patient underwent unilateral PNE (S3) because of an anatomic deformity of the os sacrum. In 20 cases the conventional PNE-test (cPNE) was successful according to standard criteria (47.6 % of all cPNE). The response rate of "two-stage implantation" with implantation of the permanent electrodes was 81.8 % (9 of 11 patients)., Conclusions: The success rate of implantation of permanent neurostimulation electrodes in selecting patients for the permanent implant is significantly higher than the conventional PNE. In this group patients with neurogenic and overactive bladder dysfunctions showed the highest response rates to sacral nerve stimulation and are the most likely to benefit from sacral neuromodulation.

Objective: To investigate different stimulation signals for the peripheral nerve evaluation test (PNE, carried out before implanting a sacral neuromodulator for functional voiding dysfunction) in an animal model and to determine their efficacy, as up to 80% of patients do not respond to the PNE test., Materials and Methods: PNE foramen electrodes were placed in the S3 of 12 anaesthetized Göttingen minipigs. First, detrusor instabilities were induced by the intravesical instillation of formalin. A 10-min stimulation phase with both a quasi-trapezoidal (QT) signal and a rectangular signal followed. An interval of 30 min elapsed between the series of stimulations. The attained bladder pressure values were registered on a urodynamic unit and evaluated as contractions and amplitudes per minute. Six minipigs were treated in the same way but were not stimulated and served as a control group., Results: After formalin instillation, the mean (sd) number of involuntary detrusor contractions was 3.5 (0.8)/min and the sum of amplitudes 7.2 (1.1) cmH2O/min. Subsequent NaCl instillation and QT-stimulation reduced the contractions to 0.3 (0.3)/min and the sum of amplitudes to 0.8 (0.4) cmH2O/min. Stimulation with a rectangular signal, as used in the PNE test, followed after an interval of 10 min, giving 1.1 (0.1) contractions/min and a sum of amplitudes of 5.1 (2.4) cmH2O/min. Within the control group there was no significant reduction., Conclusions: These results show that QT-stimulation suppresses uncontrollable detrusor contractions in the minipig more effectively than the conventional rectangular stimulation presently applied in sacral neuromodulation.

Objective: Aim of this study was to evaluate whether the carbachol test and the nerve lesions responsible for bladder dysfunction possess predictive value in patients with chronic urinary retention who undergo temporary sacral neuromodulation (PNE test)., Material and Methods: In 1999 and 2000, PNE tests were performed in 24 patients with chronic urinary retention and acontractile detrusor previously assessed by urodynamics. In 18 patients, a carbachol test was performed during urodynamics. The diagnosis related to the acontractile detrusor was additionally assessed and compared to the successful outcome of the PNE test., Results: The PNE test was successful in 8 of the 24 patients (33.3 %). The bladder was completely emptied during the PNE test in 3 of the 10 patients with negative carbachol test and in 3 of the 8 patients with positive carbachol test. The highest success rate (80 %) was observed in patients after hysterectomy, whereas after lumbosacral pulposal prolapse or with a CNS tumor, it was only 20 - 33.3 %., Conclusions: We conclude that sacral neuromodulation is an effective treatment option in patients with nonobstructive urinary retention. The carbachol test does not possess any definitive predictive value with respect to the success rate of sacral neuromodulation in patients with chronic urinary retention. The success rate more likely depends on the localisation of the nerve lesion. PNE tests should be performed in all patients with therapy resistent nonobstructive urinary retention, as no other predictive factors exist.

Purpose: Prior to implantation of a sacral neuromodulator we carried out PNE tests (peripheral nerve evaluation test) with bilateral test stimulation to establish which patients might profit from this kind of therapy. In contrast to the original unilateral technique used by Tanagho and Schmidt, we performed bilateral PNE test stimulation. Moreover, we analysed the diagnostic characteristics of those patients who had positive PNE test results and could thus receive a chronic sacral neuromodulator., Materials and Methods: We performed bilateral PNE test stimulation in 70 patients (mean age: 53.6 yrs; 41 with retention symptoms and 29 with a hyperactive detrusor) over a minimum of 3 days. Retrospectively, we analysed the distribution of diagnostic characteristics (retention vs. overactive bladder and neurogenic vs. idiopathic) in the implant recipients., Results: All patients received bilateral PNE test stimulation, during which the stimulation amplitudes were adjusted individually for each side. 8 patients were treated with the original PNE-electrode (model 0 041 830 - 002, Medtronic Inc., USA) without success. Of the remaining 62 patients, who were treated with an improved electrode, the PNE test was successful in 32 cases (51.6 %). Twenty-seven of these patients suffered from a neurogenic bladder dysfunction, and, in 5 cases, the causes were idiopathic., Conclusions: Bilateral PNE-test stimulation and the use of advanced PNE electrodes (model 3057, Medtronic Inc., USA) led to a positive PNE result in 51.6 % of the tested patients. Of these, the group with neurogenic bladder dysfunctions showed the highest response rate. Compared with the success rates in the multicenter study, we were able to increase the overall PNE response rate significantly. For this reason, we prefer a bilateral PNE-test with side-specific stimulation.

The aim of this study was to evaluate the percutaneous nerve evaluation (PNE) test success in patients with nonobstructive urinary retention. A total of 24 PNE tests were performed in patients with nonobstructive urinary retention and in 18 patients, a carbachol test was performed during urodynamics. The diagnosis relating to the acontractile detrusor was also assessed and compared to the outcome of the PNE test. The PNE test was successful in eight of 24 patients (33.3%) with the the highest success rate being observed in patients after hysterectomy (80%). It was successful in five of 12 patients with negative carbachol tests and in three of six patients with positive carbachol tests. We conclude that sacral neuromodulation is an effective treatment option in patients with nonobstructive urinary retention. PNE tests should be performed in all patients with therapy resistant nonobstructive urinary retention, because predictive factors do not exist.

Objectives: Sacral neuromodulation represents chronic stimulation of the sacral (S3) nerve. So far, the mode of action and neuro-anatomical basis is unclear. Sacral reflex mechanisms as well as pontine or cortical centers of modulation have been postulated. Our aim was to evaluate possible alterations in electroencephalogram (EEG) activity as an indicator of a supraspinally mediated mechanism of sacral neuromodulation., Materials and Methods: We analyzed serial EEGs (apparatus: Kölner Vitaport System) using electrodes placed at Fz, Cz, Cz' and Pz in 10 patients. Subsequently, the sacral (S3) nerve was stimulated by means of an impulse generator (Medtronic, Interstim 3023) using an on-off paradigm with a 1.5s "on" interval followed by a 10s stimulation break. Raw data were analyzed using both Matlab 4.0 software and a specially developed averaging routine., Results: All patients demonstrated a cortical potential complex following sacral root stimulation with an early electronegative component at 50 ms with a mean amplitude of 23 microV followed by a late potential component with a mean latency of 253 ms and a mean amplitude of 5 microV, both with a maximum at Cz, corresponding to the post-central gyrus. This finding occurred irrespective of patient's reports of actually feeling the neuromodulator being switched on and off., Conclusion: In neuromodulation responders, both short and long latency cortical potentials can be reproduced with a maximum at the sensory cortical area. Although these potentials are similar to cognitively mediated "event-related potentials", they are clearly distinct from any subjective sensory or even painful response since several patients of this series have not been able to feel any neuromodulator action. Therefore, this pilot study indicates a supraspinally mediated site of modulation, most probably in sensory cortex areas.

The implantable neuromodulation system described by Tanagho and Schmidt enables unilateral sacral nerve stimulation. Reports have been made on sacral neuromodulation failures of up to 50% in patients undergoing this procedure. We chose the bilateral electrode implantation and a minimal invasive laminectomy to ensure a more effective modulation and better placement and fixation of the electrodes. After successful assessment using a peripheral nerve evaluation test, 20 patients (14 with detrusor instability, 6 with hypocontractile detrusor) underwent minimally invasive laminectomy and bilateral electrode placement. In the patients with detrusor instability, the incontinence episodes were reduced from 7.2 to 1 per day and the bladder capacity improved from 198 to 352 ml. In patients with hypocontractile detrusor, the initial residual urine level of 450 ml dropped to 108 ml. Maximum detrusor pressure during micturition rose from 12 cmH2O initially to 34 cmH2O. The average follow up period was 17.5 months. There was no sign of deterioration in the modulation effect in any of the patients. Bilateral electrode implantation and the new sacral approach allow optimal neuromodulation in patients with bladder dysfunction. Laminectomy enables optimum electrode placement and fixation with minimal trauma.

Purpose: Cryotechnique for selective block of the urethral sphincter and simultaneous activation of the bladder was developed to achieve physiological micturition during sacral anterior root stimulation (SARS)., Materials and Methods: In ten foxhounds SARS of S2 was carried out while extradurally both spinal nerves S2 were cooled down from positive 25C in a stepwise fashion until a sphincter block was observed. Subsequently, SARS of S2 was performed while the pudendal nerves were cooled down from + 15C. The effects of spinal and pudendal nerve cold block on the urethral sphincter and bladder during SARS and the recovery time were monitored by urodynamic investigation., Results: A complete cold block of the urethral sphincter during spinal nerve cooling was achieved in all cases. During pudendal nerve cooling, the sphincter was completely blocked in two, and incompletely blocked in four dogs. Cold block temperature of the spinal nerves averaged +11.7C and of the pudendal nerves +6.2C. During SARS and spinal nerve cooling, an increase in intravesical pressure up to 13 cm. water was recognized, and recovery time was on average 6.6 minutes. Intravesical pressure remained unchanged during pudendal nerve cooling, with recovery time being less than 1 minute. The cold block was always reversible., Conclusions: Cryotechnique is an excellent method for selective and reversible block of the urethral sphincter during SARS to avoid detrusor-sphincter-dyssynergia. The application of cryotechnique in functional electrical stimulation leads to an improvement of quality of life in para- or tetraplegic patients because of selective nerve stimulation with optimization of micturition, standing, walking and grasping and does so without the necessity of surgical dorsal root rhizotomy.