Economic consequences of an implanted neuroprosthesis for bladder and bowel management

Neurostimulation on lumbosacral nerves as a new treatment for spinal cord injury impairments and its impact on cortical activity: a narrative review

Spinal cord injury (SCI) can cause significant motor, sensory, and autonomic dysfunction by disrupting neural connections. As a result, it is a global health challenge that requires innovative interventions to improve outcomes. This review assesses the wide-ranging impacts of SCI and focuses on the laparoscopic implantation of neuroprosthesis (LION) as an emerging and promising rehabilitation technique. The LION technique involves the surgical implantation of electrodes on lumbosacral nerves to stimulate paralyzed muscles. Recent findings have demonstrated significant improvements in mobility, sexual function, and bladder/bowel control in chronic SCI patients following LION therapy. This manuscript revisits the potential physiological mechanisms underlying these results, including neuroplasticity and modulation of autonomic activity. Additionally, we discuss potential future applications and amendments of LION therapy. This study emphasizes the potential of neuromodulation as a complementary approach to traditional rehabilitation, that can provide a beacon of hope for improving functionality and quality of life for individuals with SCI.

Neuroprosthesis for individuals with spinal cord injury

OBJECTIVE

Individuals who sustain a traumatic spinal cord injury (SCI) often have a loss of multiple body systems. Significant functional improvement can be gained by individual SCI through the use of neuroprostheses based on electrical stimulation. The most common actions produced are grasp, overhead reach, trunk posture, standing, stepping, bladder/bowel/sexual function, and respiratory functions.

METHODS

We review the fundamental principles of electrical stimulation, which are established, allowing stimulation to be safely delivered through implanted devices for many decades. We review four common clinical applications for SCI, including grasp/reach, standing/stepping, bladder/bowel function, and respiratory functions. Systems used to implement these functions have many common features, but are also customized based on the functional goals of each approach. Further, neuroprosthetic systems are customized based on the needs of each user.

RESULTS & CONCLUSION

The results to date show that implanted neuroprostheses can have a significant impact on the health, function, and quality of life for individuals with SCI. A key focus for the future is to make implanted neuroprostheses broadly available to the SCI population.

Adapting the Finetech-Brindley Sacral Anterior Root Stimulator for Bioelectronic Medicine. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:6406-6411. [PMID: 34892578 DOI: 10.1109/embc46164.2021.9630995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The Finetech-Brindley Sacral Anterior Root Stimulator (SARS) is a low cost and reliable system. The architecture has been used for various bioelectric treatments, including several thousand implanted systems for restoring bladder function following spinal cord injury (SCI). Extending the operational frequency range would expand the capability of the system; enabling, for example, the exploration of eliminating the rhizotomy through an electrical nerve block. The distributed architecture of the SARS system enables stimulation parameters to be adjusted without modifying the implant design or manufacturing. To explore the design degrees-of-freedom, a circuit simulation was created and validated using a modified SARS system that supported stimulation frequencies up to 600 Hz. The simulation was also used to explore high frequency (up to 30kHz) behaviour, and to determine the constraints on charge delivered at the higher rates. A key constraint found was the DC blocking capacitors, designed originally for low frequency operation, not fully discharging within a shortened stimulation period. Within these current implant constraints, we demonstrate the potential capability for higher frequency operation that is consistent with presynaptic stimulation block, and also define targeted circuit improvements for future extension of stimulation capability.

Sacral Anterior Root Stimulation and Visceral Function Outcomes in Spinal Cord Injury-A Systematic Review of the Literature Over Four Decades

OBJECTIVE

Sacral anterior root stimulation (SARS) was developed 40 years ago to restore urinary and bowel functions to individuals with spinal cord injury. Mostly used to restore lower urinary tract function, SARS implantation is coupled with sacral deafferentation to counteract the problems of chronic detrusor sphincter dyssynergia and detrusor overactivity. In this article, we systematically review 40 years of SARS implantation and assess the medical added value of this approach in accordance with the PRISMA guidelines. We identified 4 axes of investigation: 1) impact on visceral functions, 2) implantation safety and device reliability, 3) individuals' quality of life, and 4) additional information about the procedure.

METHODS

A systematic review was performed. Three databases were consulted: PubMed, EBSCOhost, and Pascal. A total of 219 abstracts were screened and 38 articles were retained for analysis (1147 implantations).

RESULTS

The SARS technique showed good clinical results (85.9% of individuals used their implant for micturition and 67.9% to ease bowel movements) and improved individual quality of life. Conversely, several sources of complications were reported after implantation (e.g., surgical complications and failure).

CONCLUSIONS

Despite promising results, a decline in implantations was observed. This decline can be linked to the complication rate, as well as to the development of new therapeutics (e.g., botulinum toxin) and directions for research (spinal cord stimulation) that may have an impact on people. Nevertheless, the lack of alternatives in the short-term suggests that the SARS implant is still relevant for the restoration of visceral functions after spinal cord injury.

Current State of Knowledge on Digital Rectal Stimulation in Individuals With Traumatic and Nontraumatic Spinal Cord Injury: A Scoping Review

OBJECTIVES

To map and characterize the nature of the evidence on the use of digital rectal stimulation for bowel management in individuals with spinal cord injury (SCI).

DATA SOURCES

Five electronic databases were searched (ie, MEDLINE, EMBASE, CINAHL, Cochrane CENTRAL, and Cochrane Incontinence Group) from 1990 to November 2019.

STUDY SELECTION

Articles that provided information on the use of digital rectal stimulation either alone or in combination with treatments were included. Title and abstract screening was split between 2 reviewers after reaching consensus on the first 100 studies screened. Full-texts were reviewed independently by 2 reviewers. Discrepancies were resolved by a third reviewer.

DATA EXTRACTION

The data extraction form was developed by 2 reviewers and piloted. Data were extracted by one reviewer and checked for accuracy by a second reviewer.

DATA SYNTHESIS

A total of 4841 studies were screened, including 425 full text articles; 33 articles were identified. Thirty-two studies focused solely on individuals with SCI and 1 study explored the experiences of caregivers of individuals with SCI. The majority of participants were aged between 30 and 59 years old. Most studies used quantitative methods (n=30, 91%). Fourteen of the studies (42%) were cross-sectional. Within experimental or quasiexperimental designs, digital rectal stimulation was commonly studied as an adjunct to other methods such as suppositories or enemas. Incontinence and defecation time were the most commonly examined outcomes.

CONCLUSION

There were few studies found that focus on digital rectal stimulation. Further studies examining experience, effectiveness, complications, and long-term outcomes are warranted.

Bowel Outcome Prediction After Traumatic Spinal Cord Injury: Longitudinal Cohort Study

Background. Predicting functional outcomes after traumatic spinal cord injury (SCI) is essential for counseling, rehabilitation planning, and discharge. Moreover, the outcome prognosis is crucial for patient stratification when designing clinical trials. However, no valid prediction rule is currently available for bowel outcomes after a SCI. Objective. To generate a model for predicting the achievement of independent, reliable bowel management at 1 year after traumatic SCI. Methods. We performed multivariable logistic regression analyses of data for 1250 patients with traumatic SCIs that were included in the European Multicenter Study about Spinal Cord Injury. The resulting model was prospectively validated on data for 186 patients. As potential predictors, we evaluated age, sex, and variables from the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) and the Spinal Cord Independence Measure (SCIM), measured within 40 days of the injury. A positive outcome at 1 year post-SCI was assessed with item 7 of the SCIM. Results. The model relied on a single predictor, the ISNCSCI total motor score—that is, the sum of muscle strengths in 5 key muscle groups in each limb. The area under the receiver operating characteristics curve (aROC) was 0.837 (95% CI: 0.815-0.859). The prospective validation confirmed high predictive power: aROC = 0.817 (95% CI: 0.754-0.881). Conclusions. We generated a valid model for predicting independent, reliable bowel management at 1 year after traumatic SCI. Its application could improve counseling, optimize patient-tailored rehabilitation planning, and become crucial for appropriate patient stratification in future clinical trials.

Economic Consequences of an Implanted Neuroprosthesis in Subjects with Spinal Cord Injury for Restoration of an Effective Cough

Objective: To determine if an implanted neuroprosthesis for restoration of an effective cough is less costly than conventional methods of respiratory management. Methods: Nonrandomized clinical trial of participants (N = 14) with spinal cord injury (SCI) using the Cough Stimulator device in the inpatient hospital setting for Cough Stimulator implantation and outpatient hospital or residence for follow-up. A neuroprosthesis was implanted for restoration of an effective cough. The annual costs associated with respiratory management, without (pre implantation) and with (post implantation) the neuroprosthesis, were examined over a 4-year period. Results: The total cost related to implantation of the Cough Stimulator was $59,891, with no maintenance costs over subsequent years. The incidence of respiratory tract infections and the need for caregiver support fell significantly following implantation. The costs associated with respiratory tract infections fell significantly from a mean of $36,406 ± 11,855/year to $13,284 ± 7,035/year (p < .05) pre and post implantation, respectively. Costs fell further to $8,817 ± 5,990 and $4,467 ± 4,404 following the 2nd and 3rd years post implantation (p < .05), respectively. The costs associated with caregiver support fell significantly from $25,312 ± 8,019/year to $2,630 ± 2,233/year (p < .05) pre and post implantation, respectively, and remained low in subsequent years (p < .05). Other costs related to secretion management fell significantly and remained low in subsequent years (p < .05). Break-even analysis demonstrated that this point was reached in the first year. Conclusion: The results of this investigation demonstrate that implantation and use of the Cough Stimulator resulted in significant reductions in the overall costs of respiratory management in this patient population.

Prediction of Bladder Outcomes after Traumatic Spinal Cord Injury: A Longitudinal Cohort Study

BACKGROUND

Neurogenic bladder dysfunction represents one of the most common and devastating sequelae of traumatic spinal cord injury (SCI). As early prediction of bladder outcomes is essential to counsel patients and to plan neurourological management, we aimed to develop and validate a model to predict urinary continence and complete bladder emptying 1 y after traumatic SCI.

METHODS AND FINDINGS

Using multivariate logistic regression analysis from the data of 1,250 patients with traumatic SCI included in the European Multicenter Spinal Cord Injury study, we developed two prediction models of urinary continence and complete bladder emptying 1 y after traumatic SCI and performed an external validation in 111 patients. As predictors, we evaluated age, gender, and all variables of the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) and of the Spinal Cord Independence Measure (SCIM). Urinary continence and complete bladder emptying 1 y after SCI were assessed through item 6 of SCIM. The full model relies on lower extremity motor score (LEMS), light-touch sensation in the S3 dermatome of ISNCSI, and SCIM subscale respiration and sphincter management: the area under the receiver operating characteristics curve (aROC) was 0.936 (95% confidence interval [CI]: 0.922-0.951). The simplified model is based on LEMS only: the aROC was 0.912 (95% CI: 0.895-0.930). External validation of the full and simplified models confirmed the excellent predictive power: the aROCs were 0.965 (95% CI: 0.934-0.996) and 0.972 (95% CI 0.943-0.999), respectively. This study is limited by the substantial number of patients with a missing 1-y outcome and by differences between derivation and validation cohort.

CONCLUSIONS

Our study provides two simple and reliable models to predict urinary continence and complete bladder emptying 1 y after traumatic SCI. Early prediction of bladder function might optimize counselling and patient-tailored rehabilitative interventions and improve patient stratification in future clinical trials.

A cost-utility analysis of sacral anterior root stimulation (SARS) compared with medical treatment in patients with complete spinal cord injury with a neurogenic bladder

BACKGROUND CONTEXT

Sacral anterior root stimulation (SARS) and posterior sacral rhizotomy restores the ability to urinate on demand with low residual volumes, which is a key for preventing urinary complications that account for 10% of the causes of death in patients with spinal cord injury with a neurogenic bladder. Nevertheless, comparative cost-effectiveness results on a long time horizon are lacking to adequately inform decisions of reimbursement.

PURPOSE

This study aimed to estimate the long-term cost-utility of SARS using the Finetech-Brindley device compared with medical treatment (anticholinergics+catheterization).

STUDY DESIGN/SETTINGS

The following study design is used for the paper: Markov model elaborated with a 10-year time horizon; with four irreversible states: (1) initial treatment, (2) year 1 of surgery for urinary complication, (3) year >1 of surgery for urinary complication, and (4) death; and reversible states: urinary calculi; Finetech-Brindley device failures.

PATIENT SAMPLE

The sample consisted of theoretical cohorts of patients with a complete spinal cord lesion since ≥1 year, and a neurogenic bladder.

OUTCOME MEASURES

Effectiveness was expressed as quality adjusted life years (QALYs). Costs were valued in EUR 2013 in the perspective of the French health system.

METHODS

A systematic review and meta-analyses were performed to estimate transition probabilities and QALYs. Costs were estimated from the literature, and through simulations using the 2013 French prospective payment system classification. Probabilistic analyses were conducted to handle parameter uncertainty.

RESULTS

In the base case analysis (2.5% discount rate), the cost-utility ratio was 12,710 EUR per QALY gained. At a threshold of 30,000 EUR per QALY the probability of SARS being cost-effective compared with medical treatment was 60%. If the French Healthcare System reimbursed SARS for 80 patients per year during 10 years (anticipated target population), the expected incremental net health benefit would be 174 QALYs, and the expected value of perfect information (EVPI) would be 4.735 million EUR. The highest partial EVPI is reached for utility values and costs (1.3-1.6 million EUR).

CONCLUSIONS

Our model shows that SARS using Finetech-Brindley device offers the most important benefit and should be considered cost-effective at a cost-effectiveness threshold of 30,000 EUR per QALY. Despite a high uncertainty, EVPI and partial EVPI may indicate that further research would not be profitable to inform decision-making.

Functional electrical stimulation and spinal cord injury

Spinal cord injuries (SCI) can disrupt communications between the brain and the body, resulting in loss of control over otherwise intact neuromuscular systems. Functional electrical stimulation (FES) of the central and peripheral nervous system can use these intact neuromuscular systems to provide therapeutic exercise options to allow functional restoration and to manage medical complications following SCI. The use of FES for the restoration of muscular and organ functions may significantly decrease the morbidity and mortality following SCI. Many FES devices are commercially available and should be considered as part of the lifelong rehabilitation care plan for all eligible persons with SCI.

Electrical stimulation for the treatment of lower urinary tract dysfunction after spinal cord injury

Electrical stimulation for bladder control is an alternative to traditional methods of treating neurogenic lower urinary tract dysfunction (NLUTD) resulting from spinal cord injury (SCI). In this review, we systematically discuss the neurophysiology of bladder dysfunction following SCI and the applications of electrical stimulation for bladder control following SCI, spanning from historic clinical approaches to recent pre-clinical studies that offer promising new strategies that may improve the feasibility and success of electrical stimulation therapy in patients with SCI. Electrical stimulation provides a unique opportunity to control bladder function by exploiting neural control mechanisms. Our understanding of the applications and limitations of electrical stimulation for bladder control has improved due to many pre-clinical studies performed in animals and translational clinical studies. Techniques that have emerged as possible opportunities to control bladder function include pudendal nerve stimulation and novel methods of stimulation, such as high frequency nerve block. Further development of novel applications of electrical stimulation will drive progress towards effective therapy for SCI. The optimal solution for restoration of bladder control may encompass a combination of efficient, targeted electrical stimulation, possibly at multiple locations, and pharmacological treatment to enhance symptom control.

Comparative cost-effectiveness analysis of sacral anterior root stimulation for rehabilitation of bladder dysfunction in spinal cord injured patients

BACKGROUND

Urinary disorders account for 10% of deaths in patients with complete spinal cord injury. Sacral anterior root stimulation (SARS) may be a valuable therapeutic option to restore complete and voluntary micturition (CVM), but questions on its cost-effectiveness remain.

OBJECTIVE

To evaluate the cost-effectiveness of SARS to restore CVM in patients with complete spinal cord injury.

METHODS

We conducted a nonrandomized, multicenter, parallel-group cohort study comparing SARS vs. current medical treatments with catheterization or reflex micturition. CVM was assessed at 12 months (end of follow-up) by urodynamic examination. Medical and nonmedical costs were measured in the perspective of the French national health insurance. Linear regression models were used to estimate the incremental net benefit ((Equation is included in full-text article.); λ = willingness-to-pay) adjusted for potential confounders, and P (INB >0) (i.e., probability of SARS being cost-effective vs medical treatment) for different values of λ.

RESULTS

Twenty-five patients were included in each group in 2005 to 2009. At inclusion, mean age was 41 years; 45 (90%) patients were male, and 29 (59%) patients were paraplegic. At 12 months, 15 (60%) patients with SARS had a CVM vs. 3 (12%) patients with medical treatment (P < .001). The total mean cost was 42,803 €; and 8762 €, respectively (P < .001). After adjustment for CVM and voiding methods at inclusion, P (INB >0) was 74% at λ = 100,000 €. This probability was 94% in a sensitivity analysis excluding 6 patients presenting a CVM at inclusion.

CONCLUSION

The effectiveness and cost of SARS are much higher than for medical treatment. Our results inform decision makers of the opportunity to reimburse SARS in this vulnerable population.

Selective activation of the human tibial and common peroneal nerves with a flat interface nerve electrode

OBJECTIVE

Electrical stimulation has been shown effective in restoring basic lower extremity motor function in individuals with paralysis. We tested the hypothesis that a flat interface nerve electrode (FINE) placed around the human tibial or common peroneal nerve above the knee can selectively activate each of the most important muscles these nerves innervate for use in a neuroprosthesis to control ankle motion.

APPROACH

During intraoperative trials involving three subjects, an eight-contact FINE was placed around the tibial and/or common peroneal nerve, proximal to the popliteal fossa. The FINE's ability to selectively recruit muscles innervated by these nerves was assessed. Data were used to estimate the potential to restore active plantarflexion or dorsiflexion while balancing inversion and eversion using a biomechanical simulation.

MAIN RESULTS

With minimal spillover to non-targets, at least three of the four targets in the tibial nerve, including two of the three muscles constituting the triceps surae, were independently and selectively recruited in all subjects. As acceptable levels of spillover increased, recruitment of the target muscles increased. Selective activation of muscles innervated by the peroneal nerve was more challenging.

SIGNIFICANCE

Estimated joint moments suggest that plantarflexion sufficient for propulsion during stance phase of gait and dorsiflexion sufficient to prevent foot drop during swing can be achieved, accompanied by a small but tolerable inversion or eversion moment.

Exploratory study of perceived quality of life with implanted standing neuroprostheses

Individuals with spinal cord injury (SCI) need options for negotiating architectural barriers, completing essential transfers, and accessing items on high shelves or in cupboards that cannot be reached from the wheelchair or safely managed with reachers. Case Western Reserve University (CWRU) and the Department of Veterans Affairs (VA) have developed an assistive technology device to assist individuals with SCI to stand and transfer. The 8-channel implanted CWRU-VA system enables persons with SCI to exercise, stand, and maneuver in the vicinity of their wheelchairs. Interventions that decrease barriers to mobility and participation can have a significant effect on an individual's perceived quality of life (QOL). This study uses a qualitative research methodology comprised of a series of semi-structured interviews to determine the effects on perceived QOL of an implanted 8-channel functional electrical stimulation (FES) system for standing after SCI. The results reveal that individuals with SCI currently using an implanted FES standing system perceived significant improvements in QOL related to the neuroprosthesis. Implanted neuroprostheses for standing have the potential to improve QOL for veterans living with SCI.

Neural activity generated in the neural placode and nerve roots in the neonate with spina bifida

OBJECT

The authors conducted a study to determine the neurophysiological capacity of the neural placode in spina bifida neonates and to determine if the spinal nerve roots in these neonates had normal stimulation.

METHODS

The authors present a case series of 2 neonates born with open neural tube defects who underwent neural tube closure within 24 hours of birth. Neurophysiological monitoring and electrical stimulation of the placode and nerve roots was performed before and after closure of the neural tube.

RESULTS

Stimulation of nerve roots resulted in evoked electromyographic responses in distinct muscle groups, indicative of the myotome innervation pattern. Stimulation threshold did not change significantly after closure of the placode. Stimulation within the placode generated an alternating pattern of activity in the left and right legs.

CONCLUSIONS

Closure of the neural tube did not affect the stimulation threshold of the nerve roots, which remained easily excitable. The viability of the nerve roots suggests that they may be candidates for neural prostheses in the future. The neural placode contains basic neural elements for generating a locomotor-like pattern in response to tonic neural inputs.

High frequency sacral root nerve block allows bladder voiding

AIMS

Dyssynergic reflexive external urethral sphincter (EUS) activity following spinal cord injury can prevent bladder voiding, resulting in significant medical complications. Irreversible sphincterotomies or neurotomies can prevent EUS activation and allow bladder voiding, but may cause incontinence or loss of sacral reflexes. We investigated whether kilohertz frequency (KF) electrical conduction block of the sacral roots could prevent EUS activation and allow bladder voiding.

METHODS

The S2 sacral nerve roots were stimulated bilaterally to generate bladder pressure in six cats. One S1 nerve root was stimulated proximally (20 Hz biphasic pulse trains) to evoke EUS pressure, simulating worst-case dyssynergic EUS reflexes. KF waveforms (12.5 kHz biphasic square wave) applied to an electrode implanted distally on the S1 nerve root blocked nerve conduction, preventing the increase in EUS pressure and allowing voiding.

RESULTS

Applying KF waveforms increased bladder voiding in single, limited-duration trials from 3 ± 6% to 59 ± 12%. Voiding could be increased to 82 ± 9% of the initial bladder volume by repeating or increasing the duration of the trials.

CONCLUSIONS

Sacral nerve block can prevent EUS activation and allow complete bladder voiding, potentially eliminating the need for a neurotomy. Eliminating neurotomy requirements could increase patient acceptance of bladder voiding neuroprostheses, increasing patient quality of life and reducing the cost of patient care.

Functional electrical stimulation for bladder, bowel, and sexual function

The principles of using electrical stimulation of peripheral nerves or nerve roots for restoring useful bladder, bowel, and sexual function after damage or disease of the central nervous system are described. Activation of somatic or parasympathetic efferent nerves can produce contraction of striated or smooth muscle in the bladder, rectum, and sphincters. Activation of afferent nerves can produce reflex activation of somatic muscle and reflex inhibition or activation of smooth muscle in these organs. In clinical practice these techniques have been used to produce effective emptying of the bladder and bowel in patients with spinal cord injury and to improve continence of urine and feces. Stimulation of parasympathetic efferents can produce sustained erection of the penis, and stimulation of the nerves to the seminal vesicles can produce seminal emission. Reflex erection and ejaculation can also be produced by stimulation of afferent nerves. Experimental techniques for controlling emptying and continence by a single device, and prospects for comprehensive control of bladder, bowel, and sexual function by electrical techniques are described. These may include more selective electrodes, inactivation of nerves by specific stimulus parameters, greater use of sensors, and networking of implanted components connected to the central and peripheral nervous system.

Economic impact to employers of treatment options for cardiac arrhythmias in the US health system

OBJECTIVE

To measure relative employer-sponsored postablation costs for cardiac arrhythmias (CA), specifically atrial fibrillation (AF).

METHODS

Regression-Controlled Employee/Spouse Database study (2001 to 2008) comparing CA patients with and without ablation and AF patients with and without ablation. Regression-adjusted monthly medical, pharmacy, sick leave, and short-term disability costs were calculated 11 months before index to 36 months after index (first ablation date or average date for nonablation patients). Relative pre/postindex comparisons between ablation and nonablation cohorts were calculated and time until ablation procedure cost recovery extrapolated.

RESULTS

Few CA (280 of 11,291; 2.48%) and AF (93 of 3062; 3.04%) patients received ablation. Ablation cohorts cost less than nonablation cohorts postablation. Estimated total ablation-period costs were recovered 38 to 50 months postablation, including employee absence payment recovery within 18 months.

CONCLUSION

Current ablation use in employer-sponsored health plans may improve health care and absence costs over time.

Patient preferences for next generation neural prostheses to restore bladder function

STUDY DESIGN

A survey administered to 66 individuals with spinal cord injury (SCI) implementing a choice-based conjoint (CBC) analysis. Six attributes with three levels each were defined and used to generate choice sets with treatment scenarios. Patients were asked to choose the scenario that they preferred most.

OBJECTIVES

To determine the utility weights for treatment characteristics as well as the overall preference for the three types of neural prostheses (NP), that is Brindley, rhizotomy-free Brindley, and pudendal nerve stimulation. Earlier studies have revealed the importance of restoration of bladder function, but no studies have been performed to determine the importance of NP features.

SETTING

Two academic affiliated medical systems' SCI outpatient and inpatient rehabilitation programs, Cleveland, OH.

METHODS

CBC analysis followed by multinomial logit modeling. Individual part-worth utilities were estimated using hierarchical Bayes.

RESULTS

Side effects had the greatest significant impact on subject choices, followed by the effectiveness on continence and voiding. NPs with rhizotomy-free sacral root stimulation were preferred (45% first choice) over pudendal afferent nerve stimulation (39% second choice) and sacral root stimulation with rhizotomy (53% third choice). Almost 20% did not want to have an NP at all times.

CONCLUSION

CBC has shown to be a valuable tool to support design choices. The data showed that persons would prefer a bladder NP with minimally invasive electrodes, which would give them complete bladder function, with no side effects and that can be operated by pushing a button and they do not have to recharge themselves.

Suppression of reflex urethral responses by sacral dermatome stimulation in an acute spinalized feline model

AIMS

Reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurological injury or disease. Aberrant urethral reflexes can prevent voiding and cause serious medical complications. Characterizing these urethral reflexes during genitourinary studies is necessary for evaluating novel pharmacological or neuroprosthetic approaches. The objectives of the present study were to generate urethral reflexes in the acute spinal feline, to quantify these reflexes, and to suppress them with electrical stimulation of the sacral dermatomes.

METHODS

This study comprised eight male cats. Anaesthesia was maintained with alpha-chloralose or sodium pentobarbital. The spinal cord was transected between T10 and T12, and nerve cuff electrodes were placed on the extradural S2 sacral roots to provide bladder activation. Bladder and urethral pressures were recorded during and after bladder contractions. Electrical stimulation was applied non-invasively to the sacral dermatomes with commercial surface electrodes.

RESULTS

Urethral reflexes were elicited consistently in six cats. The corresponding urethral pressure spikes were quantified. Putative metrics of urethral reflex activity such as the rate and average magnitude of reflex pressure spikes correlated significantly with standard urodynamic variables. Electrical stimulation of the sacral dermatomes suppressed urethral reflexes in three cats.

CONCLUSIONS

These findings in an acute spinal feline preparation demonstrate a non-invasive means of suppressing undesirable urethral reflexes. Translation of this work to clinical use could improve neuroprostheses for restoring bladder function and enhance treatment of aberrant urethral reflexes in humans.

Variable patterned pudendal nerve stimuli improves reflex bladder activation

We evaluated variable patterns of pudendal nerve (PN) stimuli for reflex bladder excitation. Reflex activation of the bladder has been demonstrated previously with 20-33 Hz continuous stimulation of PN afferents. Neuronal circuits accessed by afferent mediated pathways may respond better to physiological patterned stimuli than continuous stimulation. Unilateral PN nerve cuffs were placed in neurologically intact male cats. PN stimulation (0.5-100 Hz) was performed under isovolumetric conditions at bladder volumes up to the occurrence of distension evoked reflex contractions. Stimulus evoked reflex bladder contractions were elicited in eight cats. Across all experiments, bursting of 2-10 pulses at 100-200 Hz repeated at continuous stimulation frequencies evoked significantly larger bladder responses than continuous (single pulse) stimulation (52.0+/-44.5%). Bladder excitation was also effective at 1 Hz continuous stimuli, which is lower than typically reported. Variable patterned pulse bursting resulted in greater evoked reflex bladder pressures and increased the potential stimulation parameter space for effective bladder excitation. Improved bladder excitation should increase the efficacy of neuroprostheses for bladder control.

Dorsal rhizotomy combined with anterior sacral root stimulation for neurogenic bladder

A spinal cord lesion (traumatic or not) above the sacral micturition center may induce hyperreflexia of the detrusor, spasticity of the sphincter and vesico-sphincter dyssynergia. Eventually, alterations in the upper urinary tract can be associated with increased mortality in this patient population. Sacral rhizotomies combined with implantation of an anterior sacral root stimulator appear to be an effective method not only for the treatment of voiding dysfunction but also for defecation and sexual disorders. The clinical and electrophysiological checks and the surgical technique are described. In most series, the results show a constant improvement in the patient's functional status. Ninety percent of patients gain satisfactory continence and no longer require an incontinence appliance. Bladder capacity and compliance increase dramatically. As a consequence, urinary infection rate decreases. The majority of patients remain dry, and more than 80% have a complete voiding or a post-void residue of less than 50ml and do not require any catheterization. Anterior sacral root stimulation combined with sacral posterior rhizotomy is a valuable method to restore bladder function in spinal cord-injured patients suffering from hyperactive bladder.

Minimally-invasive electrical stimulation of the pudendal nerve: a pre-clinical study for neural control of the lower urinary tract

AIMS

Electrical stimulation of afferent pudendal nerve fibers can evoke sustained bladder contractions (SBC) in cats, yet evidence of therapeutic efficacy in human subjects is lacking. This pre-clinical study was undertaken to test the hypothesis that robust bladder contractions can be generated with a minimally-invasive needle electrode.

MATERIALS AND METHODS

In seven adult cats, triggered electromyographic (EMG) signals from the external anal sphincter (EAS) were used to minimize the needle-to-nerve distance; while reflex bladder contractions were recorded as 20-sec trains of current pulses of varying amplitude (threshold to 10 mA) and frequency (1-100 Hz) were applied to the nerve. This stimulation paradigm was repeated at successively greater needle-to-nerve distances (0.5 cm intervals) and also at different electrode positions along the nerve.

RESULTS

Electrophysiological access to the pudendal nerve was consistently achieved, as indicated by the average threshold for EAS activation (0.31+/-0.19 mA). Using different combinations of stimulus amplitude and frequency, robust SBCs were evoked in every experiment. More rostral electrode positions exhibited stimulation amplitudes and corresponding maximum bladder pressures (0.68+/-0.36 mA and 25.3+/-3.5 cmH2O, respectively) that were comparable to those of more invasive stimulation methods.

CONCLUSIONS

The needle electrode provides a minimally-invasive approach that will enable the study of reflexes mediated by pudendal afferents in humans, and allow pre-operative testing before implanting a permanent device.

Sacral nerve neuromodulation for the treatment of lower bowel motility disorders

INTRODUCTION

Incontinence and constipation are common and cause a high degree of physical, social and psychological impairment. Maximal conservative therapy may improve some patients but many remain symptomatic. Surgical options are often unsatisfactory, with variable result and further options are limited. Sacral nerve stimulation uses electrical stimulation applied to the sacral nerves, eliciting a physiological effect on the lower bowel, anal sphincter and pelvic floor, resulting in clinical benefit. The objective of this study was to investigate whether sacral nerve neuromodulation can improve patients with disorders of bowel motility, when current maximal treatment has failed and to investigate the underlying physiological mechanism of action.

RESULTS

Incontinence: Nineteen patients, age 58 years (range, 37-71 years), with resistant incontinence for 6 years (range, 2-21 years) underwent stimulation. Continence improved in all at 24 months (range, 3-60 months), fourteen fully continent. Incontinent episodes decreased; 12 (range, 2-30) versus 0 (range, 0-4), P < 0.001. Urgency (P < 0.01) and quality of life improved (P < 0.05). Anal squeeze pressure (P = 0.001) and rectal sensation (P < 0.01) improved. Constipation: Four women, (aged 27-36 years) with resistant idiopathic constipation for 8-32 years underwent the first worldwide implants. Symptoms improved in all with temporary, and in three with permanent, stimulation at 8 months (range, 1-11 months). Bowel frequency increased: 1-5 versus 6-28 evacuations/3-weeks. Symptom scores and quality of life improved. Placebo effect: A double-blind, cross-over study was performed to examine placebo effect and efficacy. Once stimulation was removed, in a blinded manner, symptoms, physiological parameters and quality of life measures rapidly returned to baseline levels. Autonomic neuromodulation: Sixteen patients, median age 59 years (range, 38-71 years), were studied at 27 months (range, 2-62 years) using laser Doppler flowmetry. Chronic stimulation was at 2.8 V (range, 0.3-3.9 V). Median flux differed between none and chronic stimulation (P = 0.001). Step-wise increments caused an immediate, dose-dependent rise in flux (P < 0.0001) up to 1.0 V.

CONCLUSIONS

This research provides strong evidence that sacral nerve stimulation can improve patients with resistant incontinence and shows proof-of-concept for the treatment of constipation. The effect is unlikely to be due to placebo and the mechanism is rapidly reversible and involves a dose-dependent effect on the autonomic nerves.

Neuromuscular electrical stimulation in neurorehabilitation

This review provides a comprehensive overview of the clinical uses of neuromuscular electrical stimulation (NMES) for functional and therapeutic applications in subjects with spinal cord injury or stroke. Functional applications refer to the use of NMES to activate paralyzed muscles in precise sequence and magnitude to directly accomplish functional tasks. In therapeutic applications, NMES may lead to a specific effect that enhances function, but does not directly provide function. The specific neuroprosthetic or "functional" applications reviewed in this article include upper- and lower-limb motor movement for self-care tasks and mobility, respectively, bladder function, and respiratory control. Specific therapeutic applications include motor relearning, reduction of hemiplegic shoulder pain, muscle strengthening, prevention of muscle atrophy, prophylaxis of deep venous thrombosis, improvement of tissue oxygenation and peripheral hemodynamic functioning, and cardiopulmonary conditioning. Perspectives on future developments and clinical applications of NMES are presented.

Bladder emptying by intermittent electrical stimulation of the pudendal nerve

Persons with a suprasacral spinal cord injury cannot empty their bladder voluntarily. Bladder emptying can be restored by intermittent electrical stimulation of the sacral nerve roots (SR) to cause bladder contraction. However, this therapy requires sensory nerve transection to prevent dyssynergic contraction of the external urethral sphincter (EUS). Stimulation of the compound pudendal nerve trunk (PN) activates spinal micturition circuitry, leading to a reflex bladder contraction without a reflex EUS contraction. The present study determined if PN stimulation could produce bladder emptying without nerve transection in cats anesthetized with alpha-chloralose. With all nerves intact, intermittent PN stimulation emptied the bladder (64 +/- 14% of initial volume, n = 37 across six cats) more effectively than either distention-evoked micturition (40 +/- 19%, p < 0.001, n = 27 across six cats) or bilateral intermittent SR stimulation (25 +/- 23%, p < 0.005, n = 4 across two cats). After bilateral transection of the nerves innervating the urethral sphincter, intermittent SR stimulation voided 79 +/- 17% (n = 12 across three cats), comparable to clinical results obtained with SR stimulation. Voiding via intermittent PN stimulation did not increase after neurotomy (p > 0.10), indicating that PN stimulation was not limited by bladder-sphincter dyssynergia. Intermittent PN stimulation holds promise for restoring bladder emptying following spinal injury without requiring nerve transection.

Control of urinary bladder function with devices: successes and failures

The management of urinary tract dysfunction is crucial for the health and well-being of people with spinal cord injury. Devices, specifically catheters, play an important role in the daily regime of bladder management for most people with spinal cord injury. However, the high incidence of complications associated with the use of catheters, and the fact that the spinal segments involved in lower urinary tract control remain intact in most cord-injured people, continue to motivate research into devices that could harness the nervous system to provide greater control over lower urinary tract function. Mechanical devices discussed in this review include catheters, artificial urethral sphincters, urethral stents and intraurethral pumps. Additionally, many attempts to restore control of the lower urinary tract with electrical stimulation have been made. Stimulation sites have included: inside the bladder, bladder wall, thigh, pelvic floor, dorsal penile nerve, pelvic nerve, tibial nerve, sacral roots, sacral nerves and spinal cord. Catheters and sacral root stimulators are two techniques whose efficacy is well established. Some approaches have proven less successful and others are still in the development stage. Modifications to sacral root stimulation including posterior root stimulation, anodal blockade and high-frequency blockade as well as new techniques including intraspinal microstimulation, urethral afferent stimulation and injectable microstimulators are also discussed. No single device has yet restored the control and function of the lower urinary tract to the pre-injury state, but new techniques are bringing this possibility closer to reality.

[Brindley technique with intradural deafferentation and extradural implantation by a single sacral laminectomy]

AIM

We propose an improved technique for implanting a sacral root stimulator associated with dorsal sacral rhizotomy ("Brindley's technique") in a single intra-sacral approach.

METHOD

This novel technique only requires a single sacral laminectomy, consisting in a sacral deafferentation at the level of the dural cul-de-sac, facilitated by the anatomical identification of the sacral roots at this level.

RESULTS

Four patients underwent surgery using this technique since October 2002, resulting in a very satisfactory micturition status.

DISCUSSION

The aim of this technique, which is as rapid as the conventional intra-dural technique, is to obtain complete deafferentation and to induce non traumatic transdural motor stimulation at the same level. In this way, surgical goals can be reached more readily with greater safety than with other techniques.

Targeting recovery: priorities of the spinal cord-injured population

In the United States alone, there are more than 200,000 individuals living with a chronic spinal cord injury (SCI). Healthcare for these individuals creates a significant economic burden for the country, not to mention the physiological, psychological, and social suffering these people endure everyday. Regaining partial function can lead to greater independence, thereby improving quality of life. To ascertain what functions are most important to the SCI population, in regard to enhancing quality of life, a novel survey was performed in which subjects were asked to rank seven functions in order of importance to their quality of life. The survey was distributed via email, postal mail, the internet, interview, and word of mouth to the SCI community at large. A total of 681 responses were completed. Regaining arm and hand function was most important to quadriplegics, while regaining sexual function was the highest priority for paraplegics. Improving bladder and bowel function was of shared importance to both injury groups. A longitudinal analysis revealed only slight differences between individuals injured <3 years compared to those injured >3 years. The majority of participants indicated that exercise was important to functional recovery, yet more than half either did not have access to exercise or did not have access to a trained therapist to oversee that exercise. In order to improve the relevance of research in this area, the concerns of the SCI population must be better known and taken into account. This approach is consistent with and emphasized by the new NIH roadmap to discovery.

Artificial autonomic reflexes: using functional electrical stimulation to mimic bladder reflexes after injury or disease

Autonomic reflexes controlling bladder storage (continence) and emptying (micturition) involve spinal and supraspinal nerve pathways, with complex mechanisms coordinating smooth muscle activity of the lower urinary tract with voluntary muscle activity of the external urethral sphincter (EUS). These reflexes can be severely disrupted by various diseases and by neurotrauma, particularly spinal cord injury (SCI). Functional electrical stimulation (FES) refers to a group of techniques that involve application of low levels of electrical current to artificially induce or modify nerve activation or muscle contraction, in order to restore function, improve health or rectify physiological dysfunction. Various types of FES have been developed specifically for improving bladder function and while successful for many urological patients, still require substantial refinement for use after spinal cord injury. Improved knowledge of the neural circuitry and physiology of human bladder reflexes, and the mechanisms by which various types of FES alter spinal outflow, is urgently required. Following spinal cord injury, physical and chemical changes occur within peripheral, spinal and supraspinal components of bladder reflex circuitry. Better understanding of this plasticity may determine the most suitable methods of FES at particular times after injury, or may lead to new FES approaches that exploit this remodeling or perhaps even influence the plasticity. Advances in studies of the neuroanatomy, neurophysiology and plasticity of lumbosacral nerve circuits will provide many further opportunities to improve FES approaches, and will provide "artificial autonomic reflexes" that much more closely resemble the original, healthy neuronal regulatory mechanisms.

A review of sacral nerve stimulation for the treatment of faecal incontinence

Sacral nerve stimulation is an emerging surgical technique that uses chronic low-level electrical stimulation, applied to the nerves of the sacral plexus, to produce a clinically beneficial physiological effect on the lower bowel, pelvic floor and anal canal. Faecal incontinence is common, maximal conservative therapy may improve some patients but many require surgery. Results are variable and often unsatisfactory and further options are limited, the traditional end-point being the formation of a colostomy. Sacral nerve stimulation appears to be an alternative treatment that is successful, has low morbidity, is maintained in the medium term and associated with an improved quality of life. The technique has the advantage of a minimally invasive test procedure with high predictive value and the surgery is minor. The underlying mechanism of action although predominately neurological in nature remains to be determined. Precise patient selection is currently unclear however, results are superior to other techniques.

Restoring function after spinal cord injury

BACKGROUND

By affecting young people during the most productive period of their lives, spinal cord injury is a devastating problem for modern society. A decade ago, treating SCI seemed frustrating and hopeless because of the tremendous morbidity and mortality, life-shattering impact, and limited therapeutic options associated with the condition. Today, however, an understanding of the underlying pathophysiological mechanisms, the development of neuroprotective interventions, and progress toward regenerative interventions are increasing hope for functional restoration.

REVIEW SUMMARY

This study addresses the present understanding of SCI, including the etiology, pathophysiology, treatment, and scientific advances. The discussion of treatment options includes a critical review of high-dose methylprednisolone and GM-1 ganglioside therapy. The concept that limited rebuilding can provide a disproportionate improvement in quality of life is emphasized throughout.

CONCLUSIONS

New surgical procedures, pharmacologic treatments, and functional neuromuscular stimulation methods have evolved over the last decades that can improve functional outcomes after spinal cord injury, but limiting secondary injury remains the primary goal. Tissue replacement strategies, including the use of embryonic stem cells, become an important tool and can restore function in animal models. Controlled clinical trials are now required to confirm these observations. The ultimate goal is to harness the body's own potential to replace lost central nervous system cells by activation of endogenous progenitor cell repair mechanisms.

Permanent sacral nerve stimulation for treatment of idiopathic constipation

BACKGROUND

Constipation can usually be managed using conservative therapies. A proportion of patients require more intensive treatment. Surgery provides variable results. This paper describes an alternative approach, in which the neural control of the bowel and pelvic floor is modified, using permanent sacral nerve stimulation.

METHODS

Four women (aged 27-36 years), underwent temporary and then permanent stimulation. All had idiopathic constipation, resistant to maximal therapy, with symptoms for 8-32 years. Clinical evaluation, bowel diary, Wexner constipation score, symptom analogue score, quality of life questionnaire and anorectal physiology were completed.

RESULTS

There was a marked improvement in all patients with temporary, and in three with permanent, stimulation. Median follow-up was 8 (range 1-11) months. Bowel frequency increased from 1-6 to 6-28 evacuations per 3 weeks. Improvement occurred, at longest-follow-up, in median (range) evacuation score (4 (0-4) versus 1 (0-4)), time with abdominal pain (98 (95-100) versus 12 (0-100) per cent), time with bloating (100 (95-100) versus 12 (5-100) per cent), Wexner score (21 (20-22) versus 9 (1-20)), analogue score (22 (16-32) versus 80 (20-98)) and quality of life. Maximum anal resting and squeeze pressures increased. Rectal sensation was altered. Transit time normalized in one patient.

CONCLUSION

Permanent sacral nerve stimulation can be used to treat patients with resistant idiopathic constipation.

Electrical stimulation for the treatment of bladder dysfunction: current status and future possibilities

Electrical stimulation of peripheral nerves can be used to cause muscle contraction, to activate reflexes, and to modulate some functions of the central nervous system (neuromodulation). If applied to the spinal cord or nerves controlling the lower urinary tract, electrical stimulation can produce bladder or sphincter contraction, produce micturition, and can be applied as a medical treatment in cases of incontinence and urinary retention. This article first reviews the history of electrical stimulation applied for treatment of bladder dysfunction and then focuses on the implantable Finetech-Brindley stimulator to produce bladder emptying, and on external and implantable neuromodulation systems for treatment of incontinence. We conclude by summarizing some recent research efforts including: (a) combined sacral posterior and anterior sacral root stimulator implant (SPARSI), (b) selective stimulation of nerve fibers for selective detrusor activation by sacral ventral root stimulation, (c) microstimulation of the spinal cord, and (d) a newly proposed closed-loop bladder neuroprosthesis to treat incontinence caused by bladder overactivity.

Spinal-cord injury

More than a decade ago, spinal-cord injury meant confinement to a wheelchair and a lifetime of medical comorbidity. The physician's armamentarium of treatments was very limited, and provision of care for individuals with spinal-cord injury was usually met with frustration. Advances in the neurosciences have drawn attention to research into spinal-cord injury. Nowadays, advanced interventions provide high hope for regeneration and functional restoration. As scientific advances become more frequent, scepticism is giving way to the ideas that spinal-cord injury will eventually be repairable and that strategies to restore function are within our grasp. We address the present understanding of spinal-cord injury, its cause, pathophysiology, diagnosis, and treatment, and look at promising research avenues. We also discuss new treatment options, including functional electric stimulation and part-weight-supported walking.

An implantable neuroprosthesis for restoring bladder and bowel control to patients with spinal cord injuries: a multicenter trial

OBJECTIVE

To evaluate the safety and efficacy of an implanted neuroprosthesis for management of the neurogenic bladder and bowel in individuals with spinal cord injury (SCI).

DESIGN

Prospective study comparing bladder and bowel control before and at 3, 6, and 12 months after implantation of the neuroprosthesis.

SETTING

Six US hospitals specializing in treatment of SCI.

PATIENTS

Twenty-three neurologically stable patients with complete suprasacral SCIs.

INTERVENTION

Implantation of an externally controlled neuroprosthesis for stimulating the sacral nerves and posterior sacral rhizotomy.

MAIN OUTCOME MEASURES

Ability to urinate more than 200mL on demand and a resulting postvoid residual volume of less than 50mL.

RESULTS

At 1-year follow-up, 18 of 21 patients could urinate more than 200mL with the neuroprosthesis, and 15 of 21 had postvoid volumes less than 50mL (median, 15mL). Urinary tract infection, catheter use, reflex incontinence, anticholinergic drug use, and autonomic dysreflexia were substantially reduced. At 1-year follow-up, 15 of 17 patients reduced the time spent with bowel management.

CONCLUSIONS

Neural stimulation and posterior rhizotomy is a safe and effective method of bladder and bowel management after suprasacral SCI.