Neuromodulation through sacral nerve roots 2 to 4 with a Finetech-Brindley sacral posterior and anterior root stimulator

Acute suppression of lower limb spasm by sacral afferent stimulation for people with spinal cord injury: A pilot study

Lower limb spasm and spasticity may develop following spinal cord injury (SCI), causing hyper-excitability and increased tone, which can impact function and quality of life. Pharmaceutical interventions for spasticity may cause unwanted side effects such as drowsiness and weakness. Invasive and non-invasive electrical stimulation has been shown to reduce spasticity without these side effects. The aim of this study was to investigate the effect of sacral afferent stimulation (SAS), through surface electrical stimulation of the dorsal genital nerve (N = 7), and through implanted electrodes on the sacral afferent nerve roots, on lower limb spasm and spasticity (N = 2). Provoked spasms were interrupted with conditional SAS, where stimulation commenced following a provoked spasm, or unconditional stimulation, which was applied continuously. Conditionally and unconditionally applied SAS was shown to suppress acute provoked spasms in people with SCI. There was a statistically significant reduction in area under the curve of quadriceps electromyography during acute spasm with SAS compared to a control spasm. These results show that SAS may provide a safe, low-cost method of reducing acute spasm and spasticity in people living with SCI. SAS through implanted electrodes may also provide an additional function to sacral nerve stimulation devices.

A Multielectrode Nerve Cuff for Chronic Velocity Selective Recording in a sheep model

Supra-sacral spinal cord injury (SCI) causes loss of bladder fullness sensation and bladder over-activity, leading to retention and incontinence respectively. Velocity selective recording (VSR) of nerve roots innervating the bladder might enable identification of bladder activity. A 10-electrode nerve cuff for sacral nerve root VSR was developed and tested in a sheep model during acute surgeries and chronic implantation for 6 months. The cuff performed well, with 5.90±1.90 kΩ electrode, and <~800 Ω tissue impedance after 189 days implantation with a stable device and tissues. This is important information for assessing the feasibility of chronic VSR.Clinical Relevance-This demonstrates the manufacturing and performance of a neural interface for chronic monitoring of bladder nerve afferents with applications in urinary incontinence and retention management following SCI.

Spinal cord injury and neurogenic lower urinary tract dysfunction: what do we know and where are we going?

One of the well reported but difficult to manage symptoms of spinal cord injury (SCI) is neurogenic lower urinary tract dysfunction (NLUTD). The type of NLUTD is variable based on location and extent of injury. SCI affects more males and NLUTD is especially debilitating for men with incomplete injury. This review summarizes the anatomical basis of NLUTD in SCI and discusses current diagnostic and management strategies that are being utilized clinically. The last two sections address new innovations and emerging discoveries with the goal of increasing scientific interest in improving treatment options for people with SCI. Areas warranting further investigation are pinpointed to address current gaps in knowledge and/or appropriate technology.

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.

Transcutaneous Electrical Stimulation for Neurogenic Bladder Dysfunction Following Spinal Cord Injury: Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

To assess the efficacy of transcutaneous electrical nerve stimulation (TENS) for neurogenic bladder dysfunction secondary to spinal cord injury (SCI).

MATERIALS AND METHODS

A systematic search of MEDLINE, EMBASE, Web of Science, Scopus, and Cochrane libraries up to February 2021 was performed using PRISMA methodology. All randomized controlled trials (RCTs) that studied TENS for neurogenic bladder in a SCI population were included. The primary outcomes of interest were maximum cystometric capacity (MCC) and maximum detrusor pressure (Pdet). Meta-analysis was conducted with RevMan v5.3.

RESULTS

Six RCTs involving 353 participants were included. Meta-analysis showed that TENS significantly increased MCC (standardized mean difference 1.11, 95% confidence interval [CI] 0.08-2.14, p = 0.03, I²  = 54%) in acute SCI. No benefits were seen for maximum Pdet. TENS was associated with no major adverse events.

CONCLUSIONS

TENS may be an effective, safe intervention for neurogenic bladder dysfunction following SCI. Further studies are essential to confirm these results and more work is required to determine optimal stimulation parameters and duration of the treatment.

Ambulatory urodynamic monitoring assessment of dorsal genital nerve stimulation for suppression of involuntary detrusor contractions following spinal cord injury: a pilot study

STUDY DESIGN

A prospective interventional pilot study using within-individual comparisons.

OBJECTIVES

To assess the effect of dorsal genital nerve stimulation (DGNS) on urine-storage parameters in participants with spinal cord injury (SCI) and neurogenic detrusor overactivity (NDO) during natural bladder filling.

SETTING

The London Spinal Cord Injuries Centre at the Royal National Orthopaedic Hospital, Stanmore, UK.

METHODS

Ambulatory urodynamic monitoring (AUM) was carried out with and without DGNS, before and after a week of using DGNS at home. DGNS was applied on-demand by four participants with bladder sensation, and both continuously and intermittently by one participant with absent sensation. A Wilcoxon sign-rank test was used to test paired results of changes within an AUM session.

RESULTS

Urodynamic outcomes were improved using DGNS. Bladder capacity was increased from 244 ± 59 to 346 ± 61 ml (p = 0.0078), a mean change of 46 ± 25%. Maximum detrusor pressure was decreased from 58 ± 18 to 47 ± 18 cmH2O (p = 0.0156), a change of 17 ± 13%, and average peak detrusor pressure was decreased from 56 ± 16 to 31 ± 128 cmH2O (p = 0.0156), a mean reduction of 50 ± 19%. There was an increase in the number of detrusor contractions from the first involuntary detrusor contraction to a strong desire, urgency or incontinence, from 1.5 ± 1.4 to 4.3 ± 1.7, and an increase in time of 23 ± 22 min. There were no changes in baseline outcomes following home use of DGNS.

CONCLUSIONS

DGNS may be applied on-demand, intermittently or continuously, to increase bladder capacity, decrease storage pressures and provide extra time. Improvements were made in addition to existing antimuscarinic medication regimes.

A Urodynamic Comparison of Neural Targets for Transcutaneous Electrical Stimulation to Acutely Suppress Detrusor Contractions Following Spinal Cord Injury

Objectives

To assess and compare the effect of transcutaneous Dorsal Genital Nerve Stimulation (DGNS), Tibial Nerve Stimulation (TNS), Sacral Nerve Stimulation (SNS), and Spinal Stimulation (SS) on Neurogenic Detrusor Overactivity (NDO) and bladder capacity in people with Spinal Cord Injuries (SCI).

Materials and Methods

Seven male participants with supra-sacral SCI were tested. Standard cystometry (CMG) was performed to assess bladder activity at baseline and with stimulation applied at each site. This was conducted over four separate sessions. All stimulation was monophasic, 15 Hz, 200 μS pulses and applied at maximum tolerable amplitude. Results were analysed against individual control results from within the same session.

Results

Dorsal Genital Nerve Stimulation increased bladder capacity by 153 ± 146 ml (p = 0.016) or 117 ± 201%. DGNS, TNS and SNS all increased the volume held following the first reflex contraction, by 161 ± 175, 46 ± 62, and 34 ± 33 ml (p = 0.016, p = 0.031, p = 0.016), respectively. SS results showed small reduction of 33 ± 26 ml (p = 0.063) from baseline bladder capacity in five participants. Maximum Detrusor Pressure before leakage was increased during TNS, by 10 ± 13 cmH₂O (p = 0.031) but was unchanged during stimulation of other sites. DGNS only was able to suppress at least one detrusor contraction in five participants and reduced first peak detrusor pressure below 40 cmH₂O in these 5. Continuous TNS, SNS, and SS produced non-significant changes in bladder capacity from baseline, comparable to conditional stimulation. Increase in bladder capacity correlated with stimulation amplitude for DGNS but not TNS, SNS or SS.

Conclusion

In this pilot study DGNS acutely suppressed detrusor contractions and increased bladder capacity whereas TNS, SNS, and SS did not. This is the first within individual comparison of surface stimulation sites for management of NDO in SCI individuals.

Closed-loop stimulation of the pelvic nerve for optimal micturition

OBJECTIVE

Neural stimulation to restore bladder function has traditionally relied on open-loop approaches that used pre-set parameters, which do not adapt to suboptimal outcomes. The goal of this study was to examine the effectiveness of a novel closed-loop stimulation paradigm for improving micturition or bladder voiding.

APPROACH

We compared the voiding efficiency obtained with this closed-loop framework against open-loop stimulation paradigms in anesthetized rats. The bladder pressures that preceded voiding, and the minimum current amplitudes for stimulating the pelvic nerves to evoke bladder contractions, were first calibrated for each animal. An automated closed-loop system was used to initiate voiding upon bladder fullness, adapt the stimulation current by using real-time bladder pressure changes to classify voiding outcomes, and halt stimulation when the bladder had been emptied or when the safe stimulation limit was reached.

MAIN RESULTS

In vivo testing demonstrated that the closed-loop system achieved high voiding efficiency or VE (75.7%  ±  3.07%, mean  ±  standard error of the mean) and outperformed open-loop systems with either conserved number of stimulation epochs (63.2%  ±  4.90% VE) or conserved charge injected (32.0%  ±  1.70% VE). Post-hoc analyses suggest that the classification algorithm can be further improved with data from additional closed-loop experiments.

SIGNIFICANCE

This novel approach may be applied to an implantable device for treating underactive bladder (<60% VE), especially in cases where under- or over-stimulation of the nerve is a concern.

Translating promising strategies for bowel and bladder management in spinal cord injury

Loss of control over voiding following spinal cord injury (SCI) impacts autonomy, participation and dignity, and can cause life-threatening complications. The importance of SCI bowel and bladder dysfunction warrants significantly more attention from researchers in the field. To address this gap, key SCI clinicians, researchers, government and private funding organizations met to share knowledge and examine emerging approaches. This report reviews recommendations from this effort to identify and prioritize near-term treatment, investigational and translational approaches to addressing the pressing needs of people with SCI.

Novel Neurostimulation of Autonomic Pelvic Nerves Overcomes Bladder-Sphincter Dyssynergia

The disruption of coordination between smooth muscle contraction in the bladder and the relaxation of the external urethral sphincter (EUS) striated muscle is a common issue in dysfunctional bladders. It is a significant challenge to overcome for neuromodulation approaches to restore bladder control. Bladder-sphincter dyssynergia leads to undesirably high bladder pressures, and poor voiding outcomes, which can pose life-threatening secondary complications. Mixed pelvic nerves are potential peripheral targets for stimulation to treat dysfunctional bladders, but typical electrical stimulation of pelvic nerves activates both the parasympathetic efferent pathway to excite the bladder, as well as the sensory afferent pathway that causes unwanted sphincter contractions. Thus, a novel pelvic nerve stimulation paradigm is required. In anesthetized female rats, we combined a low frequency (10 Hz) stimulation to evoke bladder contraction, and a more proximal 20 kHz stimulation of the pelvic nerve to block afferent activation, in order to produce micturition with reduced bladder-sphincter dyssynergia. Increasing the phase width of low frequency stimulation from 150 to 300 μs alone was able to improve voiding outcome significantly. However, low frequency stimulation of pelvic nerves alone evoked short latency (19.9–20.5 ms) dyssynergic EUS responses, which were abolished with a non-reversible proximal central pelvic nerve cut. We demonstrated that a proximal 20 kHz stimulation of pelvic nerves generated brief onset effects at lower current amplitudes, and was able to either partially or fully block the short latency EUS responses depending on the ratio of the blocking to stimulation current. Our results indicate that ratios >10 increased the efficacy of blocking EUS contractions. Importantly, we also demonstrated for the first time that this combined low and high frequency stimulation approach produced graded control of the bladder, while reversibly blocking afferent signals that elicited dyssynergic EUS contractions, thus improving voiding by 40.5 ± 12.3%. Our findings support advancing pelvic nerves as a suitable neuromodulation target for treating bladder dysfunction, and demonstrate the feasibility of an alternative method to non-reversible nerve transection and sub-optimal intermittent stimulation methods to reduce dyssynergia.

Killing the goose

The regulatory framework for implanted medical devices is preventing severely impaired people from benefitting from rehabilitation research. Consequently, research effort is wasted and we are unable to use implants to reduce the costs of healthcare. The framework should be altered so that it is economically possible to get new devices for small patient groups into widespread use.

Surgical Neurostimulation for Spinal Cord Injury

Traumatic spinal cord injury (SCI) is a devastating neurological condition characterized by a constellation of symptoms including paralysis, paraesthesia, pain, cardiovascular, bladder, bowel and sexual dysfunction. Current treatment for SCI involves acute resuscitation, aggressive rehabilitation and symptomatic treatment for complications. Despite the progress in scientific understanding, regenerative therapies are lacking. In this review, we outline the current state and future potential of invasive and non-invasive neuromodulation strategies including deep brain stimulation (DBS), spinal cord stimulation (SCS), motor cortex stimulation (MCS), transcutaneous direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) in the context of SCI. We consider the ability of these therapies to address pain, sensorimotor symptoms and autonomic dysregulation associated with SCI. In addition to the potential to make important contributions to SCI treatment, neuromodulation has the added ability to contribute to our understanding of spinal cord neurobiology and the pathophysiology of SCI.

Suburothelial Bladder Contraction Detection with Implanted Pressure Sensor

Aims

Managing bladder pressure in patients with neurogenic bladders is needed to improve rehabilitation options, avoid upper tract damage, incontinence, and their associated co-morbidities and mortality. Current methods of determining bladder contractions are not amenable to chronic or ambulatory settings. In this study we evaluated detection of bladder contractions using a novel piezoelectric catheter-free pressure sensor placed in a suburothelial bladder location in animals.

Methods

Wired prototypes of the pressure monitor were implanted into 2 nonsurvival (feline and canine) and one 13-day survival (canine) animal. Vesical pressures were obtained from the device in both suburothelial and intraluminal locations and simultaneously from a pressure sensing catheter in the bladder. Intravesical pressure was monitored in the survival animal over 10 days from the suburothelial location and necropsy was performed to assess migration and erosion.

Results

In the nonsurvival animals, the average correlation between device and reference catheter data was high during both electrically stimulated bladder contractions and manual compressions (r = 0.93±0.03, r = 0.89±0.03). Measured pressures correlated strongly (r = 0.98±0.02) when the device was placed in the bladder lumen. The survival animal initially recorded physiologic data, but later this deteriorated. However, endstage intraluminal device recordings correlated (r = 0.85±0.13) with the pressure catheter. Significant erosion of the implant through the detrusor was found.

Conclusions

This study confirms correlation between suburothelial pressure readings and intravesical bladder pressures. Due to device erosion during ambulatory studies, a wireless implant is recommended for clinical rehabilitation applications.

Bladder response to acute sacral neuromodulation while treating rats in different phases of complete spinal cord injury: a preliminary study

Background:

Compared to conventional therapies, sacral neuromodulation (SNM) may offer an alternative, non-destructive treatment for SCI patients with bladder dysfunction. Understanding bladder response to SNM treatment for SCI in different phases may yield new insights for innovative use of this promising technique.

Materials and Methods:

Female Sprague-Dawley rats were used in this study to examine the effects of acute SNM on bladder reflex in complete SCI rats. All rats were anesthetized and set up for continuous saline infusion. Acute SNM treatment was implemented for about 6 hours for each rat. Cystometric parameters, including time between contractions, contraction duration, bladder peak pressure, and number of uninhibited contractions, were analyzed and compared within rats before and after SNM treatment.

Results:

For the spinally transected rats during early phase (less than two weeks post spinalization), the time between contractions and contraction duration both increased after SNM treatments, yet the increased amplitude was about or less than 20%. For the spinally transected rats with a longer days survival (about two to four weeks post spinalization), the time between contractions and contraction duration substantially increased after SNM treatment and the changes for their average values were more than 90%. For the spinally transected rats with a much longer days survival (more than five weeks post spinalization), the time between contractions and contraction duration increased after SNM treatments, yet the magnitude of changes were less than 30%.

Conclusion:

The present study suggested that the significant effectiveness of SNM for complete SCI played its role after the spinal shock phase and prior to the development of detrusor overactivity. It indicated that the time point of SNM treatment is necessary to be paid attention.

Extradural implantation of sacral anterior root stimulator in spinal cord injury patients

AIMS

To evaluate the efficacy and complications of extradural sacral anterior root stimulation (SARS) implantation in patients with neurogenic detrusor overactivity (NDO) resulting from spinal cord injury (SCI).

MATERIALS AND METHODS

A retrospective study was conducted between 2009 and 2013, on consecutive patients with NDO associated with SCI that underwent SARS implantation. We evaluated those factors related to clinical symptoms such as urinary infection rate, erections, and episodes of autonomic dysreflexia. Data from cystometric bladder capacity (CBC) and post-void residual (PVR) volume were also analyzed.

RESULTS

Of the 104 patients included in the study, 95 (91%) patients were men with a mean (standard deviation) (SD) age of 38 (10) years. Mean (SD) time between the onset of SCI and the SARS was 78.2 (59.0) months. At baseline, 95 (91%) patients had urinary infections as compared with 16 (15%) after treatment, P < 0.001. The percentage of patients that had urinary incontinence was significantly higher at baseline than that observed after SARS, 100% versus 14%, respectively, P < 0.001. Similar results were obtained regarding dysreflexia, P < 0.001. After SARS, the mean (SD) bladder capacity was 362 (108) ml and 98 (94%) patients had a bladder capacity greater than 400 ml. As regard to the adverse effects, six patients (6%) required a suburethral mesh implant and two (2%) patients had an infection, 4 and 5 months after SARS, respectively.

CONCLUSIONS

Extradural implantation of SARS seems to be an effective and safe procedure in patients with spinal cord injury and neurogenic detrusor overactivity. Neurourol. Urodynam. 35:970-974, 2016. © 2015 Wiley Periodicals, Inc.

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.

An enhancement to velocity selective discrimination of neural recordings: extraction of neuronal firing rates

This paper describes improvements to the theory of velocity selective recording (VSR) of neural signals. Action potentials are classified and differentiated based on their conduction velocities which can be calculated from concurrent neural recordings taking at different locations on a nerve. Existing work has focussed primarily on electrically evoked compound action potentials (CAPs) where only a single evoked response per velocity is recorded. This paper extends the theory of VSR to naturally occurring neural signals recorded from rat and attempts to identify the level of activity (firing rates) within particular velocity ranges.

Dysfunction of lower urinary tract in patients with spinal cord injury

Over the past 50 years, the mortality for urorenal cause in patients with spinal cord injuries (SCI) has decreased from over 75% to 2.3%, as a result of dramatic improvements in the diagnosis and management of lower urinary tract dysfunction (LUTD). The aims of this chapter are to assess the physiopathology of upper and lower motor neuron lesion on bladder and sphincter function after SCI, to give an overview of required clinical and instrumental examination and to discuss treatment modalities. Videourodynamic examination plays a key role in the assessment and follow-up of LUTD in SCI patients, in conjunction with neurophysiological and radiological examinations. The cornerstone of bladder management in SCI is clean intermittent self-catheterization, but often other treatments are needed to achieve full continence, to reduce infections and stone formation, to protect the upper urinary tract from excessive bladder pressure, and to prevent chronic renal failure. Treatments may be pharmacologic (i.e., anticholinergic drugs and botulinum toxin) or surgical (by enterocystoplasty or urinary diversion). In selected cases, neuromodulation and sacral root stimulation can be used to reduce detrusor overactivity and empty the bladder. Management of LUTD in SCI patients requires a deep knowledge of spinal cord medicine and functioning of patients with neurologic disability.

A microchannel neuroprosthesis for bladder control after spinal cord injury in rat

A severe complication of spinal cord injury is loss of bladder function (neurogenic bladder), which is characterized by loss of bladder sensation and voluntary control of micturition (urination), and spontaneous hyperreflexive voiding against a closed sphincter (detrusor-sphincter dyssynergia). A sacral anterior root stimulator at low frequency can drive volitional bladder voiding, but surgical rhizotomy of the lumbosacral dorsal roots is needed to prevent spontaneous voiding and dyssynergia. However, rhizotomy is irreversible and eliminates sexual function, and the stimulator gives no information on bladder fullness. We designed a closed-loop neuroprosthetic interface that measures bladder fullness and prevents spontaneous voiding episodes without the need for dorsal rhizotomy in a rat model. To obtain bladder sensory information, we implanted teased dorsal roots (rootlets) within the rat vertebral column into microchannel electrodes, which provided signal amplification and noise suppression. As long as they were attached to the spinal cord, these rootlets survived for up to 3 months and contained axons and blood vessels. Electrophysiological recordings showed that half of the rootlets propagated action potentials, with firing frequency correlated to bladder fullness. When the bladder became full enough to initiate spontaneous voiding, high-frequency/amplitude sensory activity was detected. Voiding was abolished using a high-frequency depolarizing block to the ventral roots. A ventral root stimulator initiated bladder emptying at low frequency and prevented unwanted contraction at high frequency. These data suggest that sensory information from the dorsal root together with a ventral root stimulator could form the basis for a closed-loop bladder neuroprosthetic.

Anatomical feasibility of performing a nerve transfer from the femoral branch to bilateral pelvic nerves in a cadaver: a potential method to restore bladder function following proximal spinal cord injury

OBJECT

Nerve transfers are an effective means of restoring control to paralyzed somatic muscle groups and have recently been shown to be effective in denervated detrusor muscle in a canine model. A cadaveric study was performed to examine the anatomical feasibility of transferring femoral muscular nerve branches to vesical branches of the pelvic nerve as a method of potentially restoring innervation to control the detrusor muscle in humans.

METHODS

Twenty cadavers were dissected bilaterally to expose pelvic and femoral muscular nerve branches. Ease of access and ability to transfer the nerves were assessed, as were nerve cross-sectional areas.

RESULTS

The pelvic nerve was accessed at the base of the bladder, inferior to the ureter, and accompanied by inferior vesical vessels. Muscular branches of the femoral nerve to the vastus medialis and intermedius muscles (L-3 and L-4 origins) were followed distally for 17.4 ± 0.8 cm. Two muscle branches were split from the femoral nerve trunk, and tunneled inferior to the inguinal ligament. One branch was moved medially toward the base of the bladder and linked to the ipsilateral pelvic nerve. The second branch was tunneled superior to the bladder and linked to the contralateral pelvic nerve. The cross-sectional area of the pelvic nerve vesical branch was 2.60 ± 0.169 mm(2) (mean ± SEM), and the femoral nerve branch at the suggested transection site was 4.40 ± 0.41 mm2.

CONCLUSIONS

Use of femoral nerve muscular branches from the vastus medialis and intermedius muscles for heterotopic nerve transfer of bilateral pelvic nerves is surgically feasible, based on anatomical location and cross-sectional areas.

S3 motor branch stimulation failure due to nerve fiber burning at the nerve-wire junction: A historical technical note

Background:

Sacral nerve stimulation is a minimally invasive procedure to treat spinal cord injured (SCI) patients with overactive bladder syndrome or nonobstructive urinary retention that is refractory to conservative treatment.

Methods:

In this paper, we report a case of traumatic cervical SCI with quadriplegia and spastic bladder, which was managed by third sacral motor branch stimulation in 1998.

Results:

In this case, stimulation-induced burning of nerve fibers was seen microscopically during the implantation surgery. At 2 weeks after the index surgery, the stimulator was removed due to ineffectiveness. We hypothesize that the stimulation settings of our stimulator were not appropriate for neural stimulation and led to neural destruction, fibrosis, and treatment failure.

Conclusion:

The device settings of stimulators used in neural stimulation should be appropriate for direct neural stimulation otherwise they can lead to neural destruction and treatment failure.

Neurostimulation for neurogenic bowel dysfunction

Background. Loss of normal bowel function caused by nerve injury, neurological disease or congenital defects of the nervous system is termed neurogenic bowel dysfunction (NBD). It usually includes combinations of fecal incontinence, constipation, abdominal pain and bloating. When standard treatment of NBD fails surgical procedures are often needed. Neurostimulation has also been investigated, but no consensus exists about efficacy or clinical use. Methods. A systematic literature search of NBD treated by sacral anterior root stimulation (SARS), sacral nerve stimulation (SNS), peripheral nerve stimulation, magnetic stimulation, and nerve re-routing was made in Pubmed, Embase, Scopus, and the Cochrane Library. Results. SARS improves bowel function in some patients with complete spinal cord injury (SCI). Nerve re-routing is claimed to facilitate defecation through mechanical stimulation of dermatomes in patients with complete or incomplete SCI or myelomeningocele. SNS can reduce NBD in selected patients with a variety of incomplete neurological lesions. Peripheral stimulation using electrical stimulation or magnetic stimulation may represent non-invasive alternatives. Conclusion. Numerous methods of neurostimulation to treat NBD have been investigated in pilot studies or retrospective studies. Therefore, larger controlled trials with well-defined inclusion criteria and endpoints are recommended before widespread clinical use of neurostimulation against NBD.

Electrical stimulation of sacral dermatomes can suppress aberrant urethral reflexes in felines with chronic spinal cord injury

AIMS

Uncoordinated reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurologic injury. Patterned stimulation of sacral afferent pathways can reduce abnormal EUS reflexes after acute spinal cord injury (SCI); however, effectiveness following chronic SCI is unknown.

METHODS

Four adult male cats were implanted with bilateral extradural sacral root electrodes to allow bladder activation and underwent subsequent spinal transection (T10-12). Nine weeks after SCI urethral and bladder pressures were recorded with and without sacral afferent stimulation. Surface electrodes were applied to sacral and lumbar dermatomes and stimulus amplitude set below the muscle fasciculation threshold. The stimulation pattern was varied by on/off times of fixed frequency at each location.

RESULTS

Reflexive EUS contractions were observed in all animals after chronic SCI. Patterned sacral dermatome stimulation reduced EUS reflex rate and amplitude in two of four cats. Suppression was dependent on both the stimulus location and pattern. Sacral locations and a stimulation pattern of (0.75 sec on, 0.25 sec off, 20 Hz) were effective in both responder animals.

CONCLUSIONS

Patterned sacral dermatome stimulation can reduce abnormal urethral reflexes following chronic SCI. Reflex suppression is dependent on both the stimulation location and stimulus pattern. Reduction of reflexive EUS activity after chronic SCI with this non-destructive and non-invasive approach may provide an advance for the treatment of detrusor-sphincter-dyssynergia.

Effects of acute sacral neuromodulation on bladder reflex in complete spinal cord injury rats

BACKGROUND

Neurogenic bladder associated with spinal cord injury (SCI) often results in serious disruption of lower urinary tract function. Compared to conventional therapies, sacral neuromodulation (SNM) may offer an alternative, non-destructive treatment for SCI patients with bladder dysfunction. Understanding bladder reflex changes following SCI and the effects of SNM may yield new insights for innovative use of this promising technique. Using a SCI rat model developed in this study, we investigated: 1) the bladder responses with different grades of bladder filling in intact and SCI rats; and 2) the effects of acute SNM on bladder reflex responses in SCI rats.

METHODS

An SCI rat model with overactive bladder was developed and evaluated in this study to examine the effects of acute SNM on bladder reflex in complete SCI rats. Twelve adult female Sprague-Dawley rats were divided into three groups; group I: spinally intact rats (N = 4), group II: transected (T9-T10) rats (N = 4), i.e., SCI rats, and group III: SCI rats with SNM treatment (N = 4). All rats were anesthetized and set up for continuous saline infusion. Cystometric parameters, including contraction period, contraction duration, bladder peak pressure, and number of uninhibited contractions, were analyzed and compared between groups and between conditions with and without SNM treatment for SCI rats.

RESULTS

In the intact rats, the frequency of bladder contraction was dependent upon the rate of bladder filling, while the spinal transected rats exhibited large fluctuation and demonstrated different patterns in response to saline infusion. Moreover, the bladder in SCI rats demonstrated an increased contraction period and a decreased contraction strength compared to the intact rats (all p < 0.05). In SCI rats under acute SNM treatment, bladder contraction period and duration tended to become longer, and the bladder peak pressure was decreased. The accumulating evidence indicated that acute SNM had inhibiting effects for bladder overactivity following SCI.

CONCLUSION

The spinal rat model developed in this study was suitable to investigate the effect of sacral neural stimulation on micturition reflex. The results of present study demonstrated that the micturition reflex can be modulated by sacral neural stimulation.

[The future of invasive neuromodulation: new techniques and expanded indications]

Due to the increasing popularity of neuromodulation, the number of indications and patient groups to which this technique is offered is also increasing. We evaluated the currently available data concerning neuromodulation in geriatric patients, children and patients with spinal cord injury and potential alternatives regarding neural targets and implantation techniques.The evidence of the use of neuromodulation in these patient groups is low. In geriatric patients, the use of neuromodulation seems to be justified. The few existing results concerning neuromulation in children are positive; however, there are no data about long term effects of neuromodulation on the growing organism. In patients with spinal cord injury, neuromodulation by microsurgical nerve anastomosis does not seem to be successful. According to the preliminary data of a single study, neuromodulation in acute spinal cord injury may prevent development of a neurogenic bladder dysfunction. The laparoscopic implantation of electrodes for neuromodulation unfolds new technical opportunities; however, until today there is no proof of the efficacy of this technique. Pudendal neuromodulation appears to be a meaningful addition to the therapeutic armamentarium for selected indications.The existing studies demonstrate the future opportunities of neuromodulation also in geriatric patients, children and patientens with spinal cord injuries. However, especially in the latter two groups, further studies concerning effectiveness and long term consequences are mandatory prior to offering these techniques to patients in everyday practise.

Active books: the design of an implantable stimulator that minimizes cable count using integrated circuits very close to electrodes

This paper presents an integrated stimulator that can be embedded in implantable electrode books for interfacing with nerve roots at the cauda equina. The Active Book overcomes the limitation of conventional nerve root stimulators which can only support a small number of stimulating electrodes due to cable count restriction through the dura. Instead, a distributed stimulation system with many tripole electrodes can be configured using several Active Books which are addressed sequentially. The stimulator was fabricated in a 0.6-μm high-voltage CMOS process and occupies a silicon area of 4.2 × 6.5 mm(2). The circuit was designed to deliver up to 8 mA stimulus current to tripole electrodes from an 18 V power supply. Input pad count is limited to five (two power and three control lines) hence requiring a specific procedure for downloading stimulation commands to the chip and extracting information from it. Supported commands include adjusting the amplitude of stimulus current, varying the current ratio at the two anodes in each channel, and measuring relative humidity inside the chip package. In addition to stimulation mode, the chip supports quiescent mode, dissipating less than 100 nA current from the power supply. The performance of the stimulator chip was verified with bench tests including measurements using tripoles in saline.

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.

Surgical access for electrical stimulation of the pudendal and dorsal genital nerves in the overactive bladder: a review

PURPOSE

The anatomy of the pudendal nerve and its nerve branches, especially the dorsal nerve of the penis and clitoris (dorsal genital nerves), and the clinical application of electrical stimulation of these nerves in patients with overactive bladder syndrome and detrusor overactivity are reviewed.

MATERIALS AND METHODS

A literature search was performed using the PubMed® database and reference lists of relevant studies to obtain articles concerning the anatomy as well as the electrical stimulation of the pudendal nerve and its nerve branches in patients with overactive bladder syndrome.

RESULTS

According to the anatomy, electrical stimulation of the pudendal nerve and the dorsal genital nerves to suppress involuntary detrusor contractions is possible at several sites along their course from the sacral nerves to the penis or clitoris. The nerves are accessible by minimally invasive percutaneous methods. Stimulation of the pudendal nerve and dorsal genital nerves effectively increases bladder capacity, and inhibits involuntary detrusor contractions and overactive bladder symptoms.

CONCLUSIONS

More clinically applied studies are recommended for stimulation of the dorsal genital nerves to assess its value and feasibility because most studies have been performed in an acute and experimental setting. The preferred type of electrode is not known, but if wire electrodes can be implanted and fixated well by a minimally invasive procedure, cuff electrodes are not necessary. Before deciding on continuous or conditional stimulation, chronic clinical studies are recommended because acute studies remain inconclusive. The feasibility of conditional stimulation depends on the availability of a reliable and clinically applicable detrusor activity sensor.

Clinical results of a brindley procedure: sacral anterior root stimulation in combination with a rhizotomy of the dorsal roots

The Brindley procedure consists of a stimulator for sacral anterior-root stimulation and a rhizotomy of the dorsal sacral roots to abolish neurogenic detrusor overactivity. Stimulation of the sacral anterior roots enables micturition, defecation, and erections. This overview discusses the technique, selection of patients and clinical results of the Brindley procedure. The Brindley procedure is suitable for a selected group of patients with complete spinal cord injury and detrusor overactivity. Overall, the Brindley procedure shows good clinical results and improves quality of life. However, to remain a valuable treatment option for the future, the technique needs some adequate changes to enable analysis of the implanted parts, to improve revision techniques of the implanted parts, and to abolish the sacral dorsal rhizotomy.

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

AIMS

To present new strategies of pelvic nerves stimulation to enhance micturition, to control spasticity, and to recover locomotion in paraplegics.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Conditional and continuous electrical stimulation increase cystometric capacity in persons with spinal cord injury

AIMS

Individuals with spinal cord injury (SCI) exhibit neurogenic detrusor overactivity (NDO) causing high intravesicle pressures and incontinence. The first aim was to measure changes in maximum cystometric capacity (MCC) evoked by electrical stimulation of the dorsal genital nerve (DGN) delivered either continuously or conditionally (only during bladder contractions) in persons with SCI. The second aim was to use the external anal sphincter electromyogram (EMG(EAS)) for real-time control of conditional stimulation.

METHODS

Serial filling cystometries were performed in nine volunteers with complete or incomplete supra-sacral SCI. Conditional stimulation was delivered automatically when detrusor pressure increased to 8-12 cmH(2)O above baseline. MCCs were measured for each treatment (continuous, conditional, and no stimulation) and compared using post-ANOVA Tukey HSD paired comparisons. Additional treatments in two subjects used the EMG(EAS) for automatic control of conditional stimulation.

RESULTS

Continuous and conditional stimulation increased MCC by 63 +/- 73 ml (36 +/- 24%) and 74 +/- 71 ml (51 +/- 37%), respectively (P < 0.05), compared to no stimulation. There was no significant difference between MCCs for conditional and continuous stimulation, but conditional stimulation significantly reduced stimulation time (174 +/- 154 sec, or 27 +/- 17% of total time) as compared to continuous stimulation (469 +/- 269 sec, 100% of total time, P < 0.001). The EMG(EAS) algorithm provided reliable detection of bladder contractions (six of six contractions over four trials) and reduced stimulation time (21 +/- 8% of total time).

CONCLUSIONS

Conditional stimulation generates increases in bladder capacity while substantially reducing stimulation time. Furthermore, EMG(EAS) was successfully used as a real-time feedback signal to control conditional electrical stimulation in a laboratory setting.

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.

Bladder inhibition or excitation by electrical perianal stimulation in a cat model of chronic spinal cord injury

OBJECTIVE

To test the hypothesis that perianal electrical stimulation (PES) in chronic spinal cord-injured (SCI) cats could induce frequency-dependent inhibitory or excitatory reflex bladder responses.

MATERIALS AND METHODS

The experiments were conducted > or =4-5 weeks after spinal cord transection at the T9-T10 level. PES was applied via a pair of hook electrodes to the perianal skin area in three awake female cats with chronic SCI. A double-lumen balloon catheter was inserted through the urethra into the bladder to monitor bladder pressure and infuse saline (2-4 mL/min).

RESULTS

Under isovolumetric conditions PES at 3-10 Hz significantly inhibited large-amplitude reflex bladder activity induced by bladder distension above the micturition volume threshold. However, PES at 20-50 Hz induced large-amplitude bladder contractions when the bladder volume was below the micturition volume threshold. Inhibitory PES (7 Hz) significantly increased the mean (sem) bladder capacity by 40 (10)% when it was applied continuously during cystometrography. The optimum excitatory PES (30 Hz) induced large-amplitude (>25 cmH(2)O), long-duration (>20 s) bladder contractions at a wide range of bladder volumes (10-90% of bladder capacity).

CONCLUSIONS

This study showed that activation of pudendal afferent fibres by PES could induce frequency-dependent reflex bladder responses in awake cats with chronic SCI, indicating that a possible noninvasive treatment based on PES could be developed to restore both continence and micturition function for patients with SCI.

Functional electrical stimulation after spinal cord injury: current use, therapeutic effects and future directions

Repair of the injured spinal cord by regeneration therapy remains an elusive goal. In contrast, progress in medical care and rehabilitation has resulted in improved health and function of persons with spinal cord injury (SCI). In the absence of a cure, raising the level of achievable function in mobility and self-care will first and foremost depend on creative use of the rapidly advancing technology that has been so widely applied in our society. Building on achievements in microelectronics, microprocessing and neuroscience, rehabilitation medicine scientists have succeeded in developing functional electrical stimulation (FES) systems that enable certain individuals with SCI to use their paralyzed hands, arms, trunk, legs and diaphragm for functional purposes and gain a degree of control over bladder and bowel evacuation. This review presents an overview of the progress made, describes the current challenges and suggests ways to improve further FES systems and make these more widely available.

Bladder inhibition or voiding induced by pudendal nerve stimulation in chronic spinal cord injured cats

AIMS

To investigate pudendal-to-bladder spinal reflexes in chronic spinal cord injured (SCI) cats induced by electrical stimulation of the pudendal nerve.

METHODS

Bladder inhibition or voiding induced by pudendal nerve stimulation at different frequencies (3 or 20 Hz) was studied in three female, chronic SCI cats under alpha-chloralose anesthesia.

RESULTS

Voiding induced by a slow infusion (2-4 ml/min) of saline into the bladder was very inefficient (voiding efficiency=7.3%+/-0.9%). Pudendal nerve stimulation at 3 Hz applied during the slow infusion inhibited reflex bladder activity, and significantly increased bladder capacity to 147.2+/-6.1% of its control capacity. When the 3-Hz stimulation was terminated, voiding rapidly occurred and the voiding efficiency was increased to 25.4+/-6.1%, but residual bladder volume was not reduced. Pudendal nerve stimulation at 20 Hz induced large bladder contractions, but failed to induce voiding during the stimulation due to the direct activation of the motor pathway to the external urethral sphincter. However, intermittent pudendal nerve stimulation at 20 Hz induced post-stimulus voiding with 78.3+/-12.1% voiding efficiency. The voiding pressures (39.3+/-6.2 cmH2O) induced by the intermittent pudendal nerve stimulation were higher than the voiding pressures (23.1+/-1.7 cmH2O) induced by bladder distension. The flow rate during post-stimulus voiding induced by the intermittent pudendal nerve stimulation was significantly higher (0.93+/-0.04 ml/sec) than during voiding induced by bladder distension (0.23+/-0.07 ml/sec).

CONCLUSIONS

This study indicates that a neural prosthetic device based on pudendal nerve stimulation might be developed to restore micturition function for people with SCI.

Refractory neurogenic detrusor overactivity

Refractory neurogenic detrusor overactivity refers to the clinical condition that is no longer manageable by anticholinergic therapy. This condition represents a formidable task to caregivers because the treatment of urinary incontinence and adequate protection of the upper urinary tract become extremely difficult. Treatment options for refractory neurogenic detrusor overactivity include detrusor injections of botulinum toxin and intravesical instillation of vanilloid compounds, mainly resiniferatoxin, or anticholinergic drugs. If these options fail, bladder augmentation or sacral anterior root stimulation offers excellent outcomes, although at much higher costs and risks to the patients.

Closed loop electrical control of urinary continence

PURPOSE

Individuals with spinal cord injury or neurological disorders may have neurogenic detrusor contractions at low volumes (bladder hyperreflexia), which cause incontinence and can lead to significant health problems. Bladder contractions can be suppressed by electrical stimulation of inhibitory pathways but continuous activation may lead to habituation of the inhibitory reflex and loss of continence. We determined whether conditional stimulation with electrical stimulation of inhibitory pathways applied only at the onset of nascent bladder contractions allows the bladder to fill to a greater volume before continence is lost compared with continuous stimulation.

MATERIALS AND METHODS

In 6 alpha-chloralose anesthetized cats cystometry was performed to compare the volume at which continence was lost under the conditions of no stimulation, continuous stimulation and conditional electrical stimulation of inhibitory pathways. PNT ENG was used to detect the onset of bladder contractions and it served as the input to an event triggered control system that regulated conditional stimulation to maintain continence.

RESULTS

Conditional stimulation controlled by PNT ENG increased bladder capacity by 36% over no stimulation and by 15% over continuous stimulation (p <0.001 and 0.027, respectively). The event triggered control system decreased stimulation time by 67% compared to continuous stimulation.

CONCLUSIONS

Conditional electrical stimulation of inhibitory pathways is more effective than continuous stimulation. A control system triggered by PNT ENG can maintain urinary continence.

Integrated control of lower urinary tract--clinical perspective

The neural mechanisms that determine social bladder control are reviewed, with a particular emphasis on the role played by sensation in the process. Much has been learnt about the neural control of the bladder from studying patients with neurological disease and those disorders that are known to disrupt bladder storage are described. Possible approaches to treatment of the resulting incontinence are reviewed and it is acknowledged that in the future, the optimal treatment for incontinence may be determined by its precise underlying pathophysiology in each instance, for example, suprapontine causes requiring different medication to spinal causes. Although the main emphasis of urological research and development so far has been the treatment of incontinence, effective therapy for other bladder disorders such an impaired emptying or bladder pain could have an important impact on the bladder symptoms of many patients.

Implantable FES system for upright mobility and bladder and bowel function for individuals with spinal cord injury

STUDY DESIGN

Postintervention.

OBJECTIVES

To determine the effectiveness of the Praxis multifunctional implantable functional electrical stimulation (FES) system (Neopraxis Pty. Ltd, Lane Cove, NSW, Australia) to provide standing and stepping ability and bladder and bowel management for individuals with motor complete thoracic level spinal cord injuries (SCI).

SETTING

Pediatric orthopedic hospital specializing in SCI.

SUBJECTS

Three males, ages 17 and 21 years, with motor-complete thoracic level SCI and intact lower motor neurons to the muscles targeted for stimulation.

METHODS

Each subject was successfully implanted with the Praxis FES system. All three subjects received electrodes for upright mobility and the first two subjects received additional electrodes for stimulated bladder and bowel management. Following training, subjects were evaluated in their ability to use FES for nine mobility activities. Acute and chronic experiments of the effect of stimulation on bowel and bladder function were also performed.

RESULTS

All three subjects could independently stand up from the wheelchair and could walk at least 6 m using a swing through gait pattern. Two subjects were able to independently perform swing through gait for 6 min and one subject was able to independently ascend and descend stairs. Suppression of reflex bladder contractions by neuromodulation (subject 1) and stimulated contractions of the rectum (subject 2) were observed in acute experiments. When stimulation was applied over the course of several weeks, a positive effect on bowel function was measured. Stimulated bladder contractions were not achieved.

CONCLUSION

The feasibility of using the Praxis FES system for upright mobility and aiding aspects of bladder and bowel function was demonstrated with three subjects with thoracic level SCI.

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.