Electrical Stimulation and Neuromodulation in Storage and Emptying Failure

Campbell-Walsh Urology, 11th Edition

PART XII

Urine Transport, Storage, and Emptying

81 Electrical Stimulation and Neuromodulation in Storage and Emptying Failure

Sandip P. Vasavada; Raymond R. Rackley

Questions

The current approved indications for sacral neuromodulation include all of the following EXCEPT:
urinary urgency.
urinary frequency.
urgency urinary incontinence.
interstitial cystitis.
idiopathic nonobstructive urinary retention.
Which patient is NOT well suited for current neuromodulation therapies?
A 65-year-old insulin-dependent diabetic man with bladder areflexia and nonobstructive urinary retention
A 67-year-old woman who has had a cerebrovascular accident and now has urinary urgency and frequency
A 41-year-old woman with urgency urinary incontinence
A 55-year-old woman who has had vaginal sling surgery and urgency urinary incontinence
A 36-year-old woman with a history of interstitial cystitis with minimal pain who voids between 20 and 25 times per day
What reflex or reflexes are responsible for modulation of bladder function?
Guarding
Bladder afferent loop
Bladder bladder
Bladder urethral
a and b
Which of the following is(are) considered the major clinical concern(s) associated with performing a sacral rhizotomy?
Pelvic pain
Creation of bladder areflexia
Abnormal sexual function
Pelvic and lower extremity sensory or motor abnormalities
c and d
The S3 sensory and motor response pattern to electrical stimulation is best described as having which one of the following?
Plantarflexion of the entire foot with sensation in the leg and buttock
Levator reflex (bellows reflex) and sensations in the leg and buttock
Dorsiflexion of the great toe and bellows reflex and pulling sensation in the rectum, scrotum, or vagina
Plantarflexion of the first three toes of the foot and sensation of pulling in the rectum or vagina
Bellows reflex (levator contraction) and sensation of pulling of the rectum
What is the main concern when performing magnetic resonance imaging (MRI) in the setting of neuromodulation and pacemaker-type devices?
Potential of dislodgement of the pacemaker
Heating of the electrical leads
Heating of the pacemaker
Potentially fatal arrhythmias
Significant neuromuscular injury risk
Which of the following represents the best clinical scenario for use of neuromodulation therapy in a patient with multiple sclerosis (MS)?
Detrusor sphincter dyssynergy
Bedridden with significant functional incontinence
Mild symptoms with no potential need for future MRI
A poorly compliant bladder
Areflexic bladder
What skeletal landmarks are associated with the S3 nerve foramen?
9 cm from the tip of the coccyx
11 cm from the tip of the coccyx
13 cm from the tip of the coccyx
The inferior aspect of the sacral iliac joints
a and d
Perhaps the main reason why neuromodulation devices are not currently approved for use in the United States by the Food and Drug Administration in pediatric patients is due to:
lack of efficacy.
potential worsening of neuromuscular function due to bony abnormalities (spina bifida and myelomeningocele).
lack of data on growth of the spinal cord and nerve roots in the setting of neuromodulation devices.
worsening of bowel function (Hinman bladder syndrome).
excellent results with noninvasive therapies (transcutaneous electrical nerve stimulation) and therefore no reason to perform more invasive sacral neuromodulation in the long term.
The best option for a patient who has undergone a failed stage I sacral neuromodulation for severe refractory urgency urinary incontinence (Medtronic [Minneapolis, MN] InterStim stage I) is:
anticholinergic therapy.
bilateral stimulation.
radical cystectomy and ileal conduit.
vaginal sling procedure.
bladder augmentation.
Which of the following statements is FALSE about the dorsal genital nerve?
Specific branches include the dorsal nerve of the penis in males and clitoral nerve in females.
It is an afferent nerve that carries sensory information.
Proximally, it carries sensory information from the hypogastric nerve.
It is a pure sensory afferent nerve branch of the pudendal nerve.
It has been proposed as a contributor to the pudendal pelvic nerve reflex.
An implantable pulse generator (IPG) infection would be best treated by:
intravenous antibiotics.
oral antibiotics.
irrigation of the pocket.
removal of the entire device.
a and b.
Which of the following statements about impedances is FALSE?
Impedance is best described as the resistance of flow of electrons through a circuit.
If there is too much resistance, no current will flow (open).
If there is too little resistance, excessive current will flow.
If there is a broken circuit, electrons cannot flow, and this will result in low impedance measurements.
Unipolar measurements are most useful for identifying open circuits during impedance testing.
Which of the following statements is FALSE about the Brindley device?
It requires intact neuron pathways between the sacral cord and nuclei, pelvic nerve, and bladder to function.
It works best in a state of long-term areflexic bladder function.
It is used most often in patients with insufficient or nonreflex micturition after spinal cord injury.
It is usually coupled with sacral posterior rhizotomy.
Electrodes are applied extradurally to S2, S3, and S4 nerve roots.
Direct electrical stimulation of the bladder often results in all of the following EXCEPT:
pelvic musculature contraction.
erection.
defecation.
bladder neck opening.
ejaculation.
Which one of the following statements regarding the use of the Brindley device is FALSE?
It requires intact neural pathways between the sacral cord and the bladder.
Sacral posterior rhizotomy is generally performed.
Myogenic decompensation is a contraindication.
Electrodes are applied extradurally to sacral roots S2 to S4.
It utilizes the principle of poststimulation voiding.
Which of the following statements regarding neurostimulation or neuromodulation is FALSE?
The desired effect of neurostimulation is through direct stimulation of nerves and muscles.
Neurostimulation is mainly reserved for neurogenic conditions.
Neurostimulation produces a delayed clinical response.
The effect of neuromodulation is achieved through alteration of neurotransmission processes.
Neuromodulation may be useful for neurogenic as well as non-neurogenic conditions.
Which of the following studies is (are) the most useful in predicting which patients will or will not respond to sacral neuromodulation?
Uroflow/postvoid residual monitoring
Voiding diary
Urodynamics/electromyography
Percutaneous lead placement and trial stimulation
c and d
Which of the following is(are) relative clinical contraindications for excluding potential candidates for neuromodulation and neurostimulation therapies?
Patients with significant anatomic abnormalities in the spine or sacrum that may present challenges to gaining access
Patients who cannot manage their devices or judge the clinical outcomes due to mental incapacitation
Patients with physical limitations that prevent them from achieving normal pelvic organ function such as functional urinary incontinence
Patients who are noncompliant
All of the above
Which of the following statements best characterizes bilateral S3 nerve root stimulation for sacral neuromodulation therapy?
It is a rational consideration for salvage therapy or added benefit as the bladder receives bilateral innervation.
It is an approach alternative to failed unilateral stimulation in patients with urinary retention.
Initial basis for this approach produced in spinal cord-injured animal models suggests this may be a potential approach in humans.
All of the above.
a and c only.
Potential sites of selective nerve stimulation other than the S3 sacral root for neuromodulation therapies for pelvic health conditions include which of the following?
S4 sacral root
Pudendal nerve
Dorsal genital nerve
Posterior tibial nerve
All of the above
When troubleshooting the complication of IPG site discomfort or pain, which of the following statements best describes the necessary action(s) needed?
Rule out IPG site infection by physical examination.
Turn off the device and ask the patient if the discomfort is still present to differentiate IPG pocket site issues from IPG electrical output-related causes.
If the IPG discomfort is output related, check whether bipolar stimulation is better than unipolar stimulation.
If IPG site discomfort is output related, check impedances because a current leak may be present from the neuroelectrode to extension lead connection.
All of the above.
When patients report recurrent symptoms after reduction or improvement of symptoms with sacral neuromodulation therapy, which of the following should be undertaken to evaluate the reason for the loss of clinical efficacy?
Check the device settings for inadvertent on/off changes and battery performance.
Evaluate the stimulation perception and anatomic localization for changes.
Check for intermittent stimulation perception via positional changes of the patient because this may suggest lead migration or a loose lead connection.
Obtain a radiograph to detect macro changes in the neuroelectrode position if findings in b and c are evident.
All of the above.

Answers

d. Interstitial cystitis.Although used commonly for interstitial cystitis (IC) symptoms, urgency/frequency IC is not truly an indication for the sacral neuromodulation devices. Several groups have seen benefits of sacral neuromodulation in IC patients, and there may be an expanding indication for this in the future.
a. A 65-year-old insulin-dependent diabetic man with bladder areflexia and nonobstructive urinary retention. It is implied that the end organ response (bladder in this case) should have good function for sacral neuromodulation and, for that matter, any form of neuromodulation to work.Neurostimulation may be different, but even if neurostimulation were used, simultaneous relaxation of the outlet would be required for a coordinated contraction and emptying phase to ensue.
e. a and b. Two important reflexes may play an important role in modulation of bladder function: the guarding reflex and the bladder afferent loop reflex. Both reflexes promote urine storage under sympathetic tone.The guarding reflex guards or prevents urine loss from times of cough or other physical stress that would normally trigger a micturition episode. Suprapontine input from the brain turns off the guarding reflex during micturition to allow efficient and complete emptying. The bladder afferent reflex works through sacral interneurons that then activate storage through pudendal nerve efferent pathways directed toward the urethral sphincter. Similar to the guarding reflex, the bladder afferent reflex promotes continence during periods of bladder filling and is quiet during micturition.
e. c and d. Bilateral anterior and posterior sacral rhizotomy or conusectomy converts a hyperreflexic bladder to an areflexic one. This alone may be inappropriate therapy because it also adversely affects the rectum, anal and urethral sphincters, sexual function, and the lower extremities.In an attempt to leave sphincter and sexual function intact, selective motor nerve section was originally introduced as a treatment to increase bladder capacity by abolishing only the motor supply responsible for involuntary contractions.
c. Dorsiflexion of the great toe and bellows reflex and pulling sensation in the rectum, scrotum, or vagina.The characteristic response of the S3 nerve distribution based on its lower innervation is to the levator musculature (bellows contraction) of the anus and ipsilateral great toe contraction. The other answers suggest either S2 stimulation (leg rotation) or S4 levator contraction.
b. Heating of the electrical leads.Although many concerns exist for MRI and pacemaker devices, it has been shown that the main concern is heating of the electrical leads. This may, in turn, traumatize blood vessels, nerve roots, or other structures that the leads themselves are next to. Currently, MRI is contraindicated in the presence of a pacemaker.
c. Mild symptoms with no potential need for future MRI.It is unknown whether subcategories of MS patients (delayed emptying/storage dysfunction, areflexia, poor compliance) would be very good candidates for sacral neuromodulation, although it is doubtful based on disease severity alone. A mildly symptomatic patient without functional issues (e.g., can get to the bathroom in time with no major mobility issues) probably would be the best patient.
e. a and d.The measurements for the rough vicinity of the S3 nerve foramen have been tested by using the "cross hair" technique (Chai et al, 2000)* and simple measurements. The answers b and c are incorrect because they represent measurements from the anal verge (11 cm), and 13 cm is too far in general from the coccyx and would likely place one near S2 or S1.
c. Lack of data on growth of the spinal cord and nerve roots in the setting of neuromodulation devices.Pediatric patients have undergone sacral neuromodulation in off-label trials, but large-scale use has been limited by lack of data on the growth of the pediatric patient and the relation of the sacral lead with regard to the sacral nerve roots, and so on. Although noninvasive therapies have worked, they are limited by the need for continued repeat therapy to maintain durability of result.
e. Bladder augmentation.The patient should have tried and failed anticholinergic therapy before having the sacral neuromodulation therapy. Scheepens and coworkers have shown that bilateral stimulation, although logical, has not been shown in urgency incontinent patients to lead to much improvement (Scheepens et al, 2002). One could argue that contralateral lead placement should be attempted, but no prospective trials have shown that this makes a difference in outcomes. The vaginal sling procedure and radical cystectomy are not indicated per se in this condition (the vaginal sling is for stress urinary incontinence, and cystectomy is too radical).
c. Proximally, it carries sensory information from the hypogastric nerve.The dorsal genital nerve is a terminal branch of the pudendal nerve and is being investigated for functional neuromodulation outcomes via a percutaneous approach. It does not carry information directly from the hypogastric nerve.
d. Removal of the entire device.Because an IPG is a foreign body, it could harbor bacteria within a biofilm created by the infection. Accordingly, it is best to have it removed in its entirety. Antibiotics and irrigation for the most part are temporizing measures. Furthermore, there is risk of an infection tracking along the sacral lead, which may create a sacral infection.
d. If there is a broken circuit, electrons cannot flow, and this will result in low impedance measurements.Impedance describes the resistance to the flow of electrons through a circuit. Impedance or resistance is an integral part of any functioning circuit; however, if there is too much resistance, no current will flow (open). If there is too little resistance, excessive current flow resulting in diminished battery longevity occurs (short). If the circuit is broken somehow, electrons cannot flow. This is called an "open" circuit, and impedance measurements are high. Open circuits can be caused by a fractured lead or extension wires, loose connections, and so on.
b. It works best in a state of long-term areflexic bladder function.The chief applications of the Brindley device are in patients with inefficient or nonreflex micturition after spinal cord injury. Prerequisites for use are described by Fischer et al (1993) as the following: (1) intact neural pathways between the sacral cord nuclei of the pelvic nerve and the bladder and (2) a bladder that is capable of contracting.
d. Bladder neck opening. The spread of current to other pelvic structures the stimulus thresholds of which are lower than that of the bladder has often resulted in (1) abdominal, pelvic, and perineal pain; (2) a desire to defecate or defecation; (3) contraction of the pelvic and leg muscles; and (4) erection and ejaculation in males. It has also been noted that the increase in intravesical pressure was generally not coordinated with bladder neck opening or with pelvic floor relaxation and that other measures to accomplish voiding may be necessary.
d. Electrodes are applied extradurally to sacral roots S2 to S4.Prerequisites for such use were described in one study as (1) intact neural pathways between the sacral cord nuclei of the pelvic nerve and the bladder and (2) a bladder that is capable of contracting. The chief application is in patients with inefficient or no reflex micturition after spinal cord injury. Simultaneous bladder and striated sphincter stimulation is obviated by sacral posterior rhizotomy, usually complete, which also (1) eliminates reflex incontinence and (2) improves low bladder compliance, if present. Electrodes are applied intradurally to the S2, S3, and S4 roots, but the pairs can be activated independently. The current Brindley stimulator uses the principle of poststimulus voiding, a term first introduced by Jonas and Tanagho (1975). Relaxation time of the striated sphincter after a stimulus train is shorter than the relaxation time of the detrusor smooth muscle. Therefore, when interrupted pulse trains instead of continuous stimulus trains are used, poststimulus voiding is achieved between the pulse trains because of the higher sustained intravesical pressure when compared with the striated sphincter.
c. Neurostimulation produces a delayed clinical response.In neurostimulation, the use of electrical stimuli on nerves and muscles has mainly been developed for achieving immediate clinical responses in neurogenic conditions of pelvic organ dysfunction, whereas in neuromodulation, the use of electrical stimuli to nerves has been developed for altering neurotransmission processes in cases of non-neurogenic as well as neurogenic conditions.
d. Percutaneous lead placement and trial stimulation.Despite all the studies done to date, there are no defined preclinical factors such as urodynamic findings that can predict which patients will or will not have a response to sacral neuromodulation. Thus, a trial of stimulation via a temporary or percutaneous lead placement is the best predictor of long-term clinical responsiveness.
e. All of the above.Whereas most patients who have failed more conservative therapies are considered candidates for neurostimulation and neuromodulation therapies, all of the above clinical considerations for excluding patients from this therapy should be considered. Furthermore, relative contraindications for patients who may be considering or who have an implantable electrical stimulation device are the issues of MRI and pregnancy.
d. All of the above.Bilateral stimulation has been suggested as an alternative, particularly in failed unilateral lead placements, for potential salvage or added benefit as the bladder receives bilateral innervation. The initial basis to consider bilateral stimulation was based on animal studies demonstrating that bilateral stimulation yielded a more profound effect on bladder inhibition than did unilateral stimulation. Only one clinical study has been performed to demonstrate the potential differences in unilateral versus bilateral stimulation (Scheepens et al, 2002). This study showed no significant difference in outcomes for unilateral versus bilateral stimulation with regard to urgency urinary incontinence, frequency, or severity of leakage in the overactive bladder group, although, overall, results were impressive in both categories. The patients in the retention group had better parameters of emptying (volume per void) in bilateral as compared with unilateral stimulation.
e. All of the above.The introduction of new stimulation methods as well as application of these methods to all the different nerve locations listed will continue to provide improved treatment alternatives, as shown in animal models and human applications. In addition, these innovations will provide the ability to further develop testable hypotheses of more basic questions on electrical neurostimulation, neuromodulation, and neurophysiology of the autonomic, somatic, and central pathways that regulate pelvic organ function.
e. All of the above.The probable causes of IPG site discomfort or pain are IPG pocket related or IPG output related. Pocket-related causes of discomfort include infection, pocket location (waistline), pocket dimension (too tight, too loose), seroma, and erosion. One should turn off the IPG and determine if the discomfort is still present to differentiate pocket-related from output-related cause. If the discomfort is persistent, the cause is not related to the IPG electrical output. In the absence of clinical signs of infection, IPG pocket-related causes such as pocket size, seroma, and erosion should be considered. If the discomfort disappears, the IPG electrical output is likely causing discomfort or pain. Output-related causes include sensitivity to unipolar stimulation if this mode is used or a current leak as demonstrated by abnormal impedances.
e. All of the above.When the patient presents with recurrent symptoms, one should evaluate the stimulation perception. The possibilities are that the patient perceives the stimulation in a wrong location as compared with baseline, has no stimulation, or has intermittent stimulation based on lead migration or mechanical issues related to a loose connection or elevated impedances.

Chapter review

The mechanism of neuromodulation may be activation of neurons that cause inhibition at spinal and supraspinal levels.
For neuromodulation to work, there must be at least some communication between sacral outflow and the pontine micturition center so as to allow for processing of reflexes that may be inhibited by the brain.
Neuromodulation has been used in fecal incontinence and constipation as well as bladder dysfunction.
Suppression of interneuronal transmission in the bladder reflex may be how sacral neuromodulation affects detrusor overactivity.
The detrusor is usually innervated primarily by S3; rectal stimulation occurs in S2, S3, and S4; and erectile stimulation is mainly a function of S2.
Transcutaneous electrical stimulation demonstrates good efficacy but has a limited role because of the constant need to administer the therapy.
Sympathetic tone, for the most part, is dominant for the majority of time and provides for continence and storage of urine; parasympathetic stimulation results in a detrusor contraction and emptying of the bladder.
There are no preclinical factors that can predict which patients will or will not respond to neuromodulation.
Two important reflexes may play an important role in modulation of bladder function: the guarding reflex and the bladder afferent loop reflex. Both reflexes promote urine storage under sympathetic tone.
Direct electrical stimulation of the bladder has often resulted in (1) abdominal, pelvic, and perineal pain; (2) a desire to defecate or defecation; (3) contraction of the pelvic and leg muscles; and (4) erection and ejaculation in males. An increase in intravesical pressure has also been noted.

^* Sources referenced can be found in Campbell-Walsh Urology, 11th Edition, on the Expert Consult website.

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