Magdy M. Hassouna

Stimulator design and subsequent stimulation parameter optimization for controlling micturition and reducing urethral resistance

An implantable computerized electrical stimulation system designed to induce bladder evacuation in animal models (dogs) after spinal cord transection has been realized and evaluated. This fully programmable system is based on a handheld device and generates a wide range of stimuli through multichannel implantable miniaturized stimulator. Using the new bladder stimulator and inducing reversible fatigue to the external sphincter via the pudendal nerve enables us to reduce the bladder outlet resistance, resulting in the proper emptying of the bladder during stimulation without the need for sacral nerve rhizotomies and the pudendal nerve neurectomies. Four chronically affected dogs were studied to determine the optimal stimulation parameters for inducing a sphincter fatigue that would reliably empty the bladder for the duration of the experiment. These parameters were: maximum amplitude of 1.5 mA +/- 0.5 SD, stimuli composed of a high frequency signal of 200 Hz +/- 50 SD modulated by a low frequency signal of 10 Hz +/- 5 SD, pulse width controlled by a duty-cycle of 20% +/- 10 SD, sacral nerve stimulation of 50 s +/- 25 SD and fatiguing duration of 20 s +/- 5 SD.

Computerized transcutaneous control of a multichannel implantable urinary prosthesis

A personal computer interface of a multichannel implantable urinary prosthesis is described. This system is composed of two main parts: the first one is internal and consists of an implant using a 4- mu m CMOS gate array chip controlling a wide variety of waveforms via eight monopolar channels; the second is an external controller featuring a versatile software, a PCB card plugged in a portable microcomputer, and a radiofrequency-coupled technique. This device is used to transmit the power, the data, and the synchronization clock to the implant by a simple binary signal modulating a 20-MHz carrier. The features of implant encapsulation and electrode design and fabrication are also reported.<<ETX>>

Efficacy of sacral neuromodulation in treatment of bladder pain syndrome: Long‐term follow‐up

This study was sought to evaluate the efficacy and durability of sacral neuromodulation in the treatment of bladder pain syndrome (BPS) patients.

A new prosthetic device for full bladder control

The design and testing of a versatile, implantable eight-channel urinary prothesis developed to restore a normal bladder function for patients with spinal-cord injuries are described. The main application of the device is the stimulation of particular nerves in the sacral roots. The intensity, the format and the timing of the current pulses available at the channel outputs are easily programmable. Those parameters are received transdermally by the implanted device in 13-bit blocks. The information is either loaded into internal registers for immediate processing or stored in an external implantable memory for a deferred processing. A miniaturized (4.51 mm*4.51 mm) implant has been implemented in 3- mu m CMOS full-custom technology, using a total of 12753 transistors. Tests have confirmed the functionality of the chip.<<ETX>>

Association Between Stimulation Parameters and Loss of Efficacy of Selective Sacral Nerve Root Stimulation

Objectives:u2002 This study sought to determine the association between stimulation parameters at the time of implantation and loss of efficacy on long‐term follow‐up.

Percutaneous Nerve Evaluation Test Versus Staged Test Trials for Sacral Neuromodulation: Sensitivity, Specificity, and Predictive Values of Each Technique

Purpose InterStim device is an U.S. Food and Drug Administration approved minimal invasive therapy for sacral neuromodulation for lower urinary tract dysfunction. Before InterStim implantation, a trial with the appropriate screening tests is required to determine patient therapy eligibility. There are two different techniques for patient screening: percutaneous nerve evaluation (PNE) test and staged test. Few studies have reported success and failure rates for each technique. However, test sensitivity and predictive values of either test have not been studied. The aim of our study was to determine the sensitivity and specificity of each test and to establish a decision algorithm for the most appropriate testing method to be used as a screening test. Methods This cross-sectional study was conducted from August 2009 to February 2012 and included patients with lower urinary tract dysfunction who participated in the stimulation test trial. Patients underwent PNE as the first stimulation test, while those who encountered technical difficulty during PNE or electrode migration underwent staged testing. Results A total of 213 patients, including 172 female and 41 male subjects, underwent PNE. The patients’ diagnoses included refractory overactive bladder (47.9%), nonobstructive urinary retention (29.6%), and frequency urgency syndrome (22.1%). A total of 202 patients were screened with PNE and 10 patients with staged testing. Overall sensitivity of PNE was 87.3%, and it was 90% for staged test. PNE specificity was 98.5% as compared to 92.9% for staged test. Positive and negative predictive values for PNE were 99% and 82.1% and for staged test were 90% and 92.9%, respectively. Conclusions PNE test has high specificity and positive predictive value. We recommend PNE, a simple office-based, less expensive procedure as the first option for screening.

Challenges in Sacral Neuromodulation

Sacral neuromodulation (SNM) is an effective and increasingly used therapeutic option for refractory urge incontinence, chronic urinary retention and symptoms of urgency-frequency. The potential for neuromodulation has also been shown in patients with interstitial cystitis and neurogenic urge incontinence secondary to refractory detrusor hyperreflexia. With the increasing number of patients, obvious concerns and challenges raised. Young female patients who desire to conceive showed concerns pertaining to neuromodulation in pregnancy including possible teratogenic effect, symptom management during pregnancy & the effect of mode of delivery on the Sacral electrode. Another concern is the need for MRI follow up in neurogenic patients. Post operative troubleshooting raises another challenge in patient management. In our chapter, we will discuss these challenges in details.

Sphincteric fatigue strategy for bladder control: preliminary chronic results in an animal model

Simultaneous sphincteric fatigue via pudendal nerves and sacral roots stimulation to induce bladder emptying have been reviewed in chronic paraplegic dogs experiments. Implantable urinary microstimulator and cylindrical cuff stainless steel electrodes have been used to perform chronic tests. Preliminary results show appropriate voiding in most animals. Estimation of average volume residue is 12.43%. Leg and tail animal flexion have been observed.

A dedicated microprocessor for urinary incontinence stimulator

A programmable memory-content readable urinary incontinence stimulator with very low power dissipation is presented in the paper. To keep the stimulated nerve from getting used to a fixed pattern of stimulation, the spaces in the stimulating pulse stream are randomly modulated. An important feature of this stimulator is its very low power dissipation, about 20 /spl mu/A in normal operation. This assures that the implant can work up to 10 years with a 3 AH lithium cell.<<ETX>>

The Role of Sacral Nerve Stimulation in Female Pelvic Floor Disorders

Female pelvic floor disorders, such as urge incontinence, nonobstructive urinary retention, painful bladder syndrome, fecal incontinence, chronic constipation, and sexual dysfunction, represent multiple challenges to the treating physicians. Sacral nerve modulation (SNM) gives a promising alternative and a minimally invasive treatment option for chronic pelvic floor disorders resistant to conventional treatment. This review covers the mechanism of action and surgical procedure of the SNM as well as the current and expanding indications for SNM in female pelvic floor disorders.