BJU International (2001), 87, 723–731
`
`Neuromodulation techniques in the treatment of the
`overactive bladder
`
`J . G R O E N and J . L . H . R . B O S C H
`Department of Urology, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands
`
`Introduction
`
`Symptoms of an overactive bladder often remain a
`therapeutic problem despite optimal use of conservative
`treatment methods including drug therapy, behavioural
`therapy, pelvic floor exercises and biofeedback. In the last
`decade, sacral nerve neuromodulation has been con-
`firmed as a valuable addition to the therapeutic arsenal.
`The success of sacral neuromodulation has renewed
`interest
`in other neuromodulation techniques. The
`current techniques of neuromodulation for treating the
`overactive bladder are:
`
`’ anogenital electrical stimulation;
`’ transcutaneous electrical nerve stimulation (TENS);
`’ sacral nerve neuromodulation;
`’ percutaneous posterior tibial nerve stimulation (Stoller
`afferent nerve stimulation, SANS);
`’ magnetic stimulation.
`
`Mechanism of action
`
`It is unknown how neuromodulation works; indeed, it is
`even unknown whether neuromodulation only works at
`the spinal level or whether supraspinal pathways are
`involved [1]. The most
`important spinal
`inhibitory
`mechanisms of the micturition reflex are [2]:
`
`’ The guarding reflex: increased activity of the striated
`urethral sphincter in response to bladder filling,
`reflexively inducing detrusor relaxation;
`’ Edvardsen’s reflex: increased activity of the sympa-
`thetic nervous system in response to bladder filling;
`’ Anal dilatation (afferent pathway: anorectal branches
`of the pelvic nerve; prevents voiding during defecation);
`’ Gentle mechanical
`stimulation of
`the
`genital
`region (afferent pathway: dorsal clitoral or penile
`branches of the pudendal nerve; prevents voiding
`during intercourse);
`
`Accepted for publication 1 March 2001
`
`# 2001 BJU International
`
`’ Physical activity; afferent pathway: muscle afferents
`from the limbs (but not from the pelvic floor!; prevents
`voiding during fighting or fleeing);
`
`Most of the afferent fibres involved in the above
`inhibitory mechanisms reach the spinal cord via the
`dorsal roots of the sacral nerves. Edvardsen’s reflex can
`also be activated by stimulation of afferent anorectal
`branches of the pelvic nerve and afferent dorsal clitoral or
`penile branches of the pudendal nerve, at least in cats. Its
`role in humans is probably limited [3].
`At least two potential mechanisms are possible: (i)
`activation of efferent fibres to the striated urethral
`sphincter reflexively cause detrusor relaxation; and (ii)
`activation of afferent fibres causes inhibition at a spinal or
`a supraspinal level. Based on experiments in dogs and
`observations in humans, Tanagho and Schmidt [4], who
`introduced sacral neuromodulation into the field of
`urology, adhered to the first theory. However, measure-
`ments of the urethral pressure profile and of urethral
`resistance during voiding do not indicate that the striated
`sphincter is activated with the stimulation parameters
`currently used [5]. Interesting studies supporting the
`second theory are those in which the dorsal clitoral or
`dorsal penile nerve, purely afferent branches of the
`pudendal nerve, were electrically stimulated. This
`induced a strong inhibition of the micturition reflex
`and detrusor hyper-reflexia in healthy volunteers and
`patients with a hyper-reflexive bladder [6–8]. Fowler et al.
`[9] measured the latency of the anal sphincter contrac-
`tion during a peripheral nerve evaluation (PNE) test in
`women who were candidates for sacral neuromodula-
`tion, and concluded that this response was mediated by a
`polysynaptic reflex rather than the result of efferent
`stimulation. Experimental work in spinalized rats showed
`that neuromodulation reduced the degree of hyper-
`reflexia as well as the expression of c-fos after bladder
`instillation with acetic acid [10]
`(C-fos protein is
`expressed in the spinal cord after irritation of the lower
`urinary tract; this expression is mainly mediated by
`afferent C fibres). This result shows that inhibition of
`afferent C fibre activity may be one of the underlying
`
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`72 4 J . G R O E N a n d J . L . H . R . BO S C H
`
`mechanisms of neuromodulation. However, it does not
`explain the beneficial effects of neuromodulation in
`patients with idiopathic detrusor instability or urgency-
`frequency. In conclusion, the mechanism of action of
`neuromodulation remains in debate. Stimulation of
`afferent pathways seems to play a crucial role.
`
`Electrical parameters
`
`Most devices available for electrical stimulation use
`bipolar
`(alternating)
`square-wave pulses
`[11]. The
`rationale of
`the bipolarity is
`the minimization of
`electrochemical reactions at the site of the electrode
`and thereby of the risk of tissue damage. A pulse duration
`of 0.2–0.5 ms has been found to be optimal in inhibiting
`the bladder, but longer pulses (1 ms) are also used.
`Physiologically, the optimal stimulation frequency is 5–
`10 Hz or even 5–6 Hz [2]. However,
`frequencies of
`<10 Hz
`soon become unpleasant when the pulse
`amplitude increases. The possible intensity of stimulation
`is therefore limited. This may explain why in some
`clinical testing the degree of bladder inhibition was
`independent of the stimulation frequency at 5–20 Hz.
`Some authors use a frequency as high as 50 Hz. The
`desired pulse amplitude depends on the neuromodulation
`technique; it should be as high as possible in anogenital
`electrical stimulation, while a value just above the
`detection threshold is considered to be sufficient in sacral
`nerve neuromodulation. Intermittent pulse trains are
`sometimes used to reduce pelvic floor muscle fatigue, but
`this mode of stimulation may not be optimal
`in the
`treatment of an overactive bladder [11].
`
`Anogenital electrical stimulation
`
`The first publications on anogenital electrical stimulation
`as a treatment option in the overactive bladder appeared
`in the 1970s [2]. Good results have been described by
`mainly Scandinavian and Japanese authors in the 1980s,
`and the technique can now be considered an established
`treatment [12]; however, satisfaction is not unanimous.
`This review focuses on comparative studies of the last
`decade.
`Technique. The method implies the insertion of plugs
`equipped with electrodes into the anal canal and (or) the
`vagina (Fig. 1); circular penile electrodes are available for
`men. Two modes of this type of neuromodulation can
`be distinguished.
`‘Long-term’ or ‘chronic’ stimulation
`implies a home-treatment programme for several months
`(e.g. 3–12). Stimulation is applied daily for many hours
`(e.g. 6–8) at a low intensity and may also take place
`during the night. This way of stimulation is mainly used
`for patients with stress incontinence and is not discussed
`here. In ‘acute’ or ‘short-term’ maximal stimulation the
`
`patient is treated in a limited number of sessions (usually
`4–20, sometimes many more) taking 15–30 min each.
`The intensity is as high as possible, i.e. just below the
`level of discomfort. Usually, this is about 1.5–2 times
`the perception threshold [13]. Treatment may take place
`weekly or during a series of consecutive days (sometimes
`twice daily) and can be undertaken in the outpatient
`clinic as well as at home. In addition to patients with an
`overactive bladder only, it may also be applied in patients
`with mixed incontinence [14]. Re-treatment may be
`useful.
`Evidence. Anogenital electrostimulation reportedly has
`a beneficial effect in about half of the patients [14,15],
`but
`the published results vary considerably. While
`Eriksen et al. [16] reported a clinical success rate of
`85% and 77% immediately after therapy and at 1 year of
`follow-up, respectively, Kulseng-Hanssen et al. [17], also
`studying women with idiopathic detrusor instability and
`urge incontinence, found no significant improvement in
`objective outcome measures, and stopped using the
`method. A closer examination of the available data is
`therefore necessary.
`A few studies have compared the effect of electro-
`stimulation with that of treatment with a sham device.
`Such a device has the same appearance as the normal
`equipment, but has no stimulus output. Most authors
`found that active treatment was symptomatically and
`cystometrically superior to sham treatment [18–20], but
`Abel et al. [21] found no significant differences, possibly
`because these authors treated postmenopausal women.
`Smith [22]
`found that
`the symptomatic result of
`intravaginal electrotherapy was at least as good as that
`of the anticholinergic propantheline bromide.
`Suitable patients. Subjective success rates of patients
`considering themselves cured or improved are as high as
`85% [16], but such rates depend heavily on the selection
`of patients. As an example, Primus and Kramer [23]
`
`Fig. 1. Plugs with electrodes for anal (left) and vaginal (right)
`stimulation.
`
`# 2001 BJU International 87, 723–731
`
`Petitioner - Avation Medical, Inc.
`Ex. 1014, p. 724
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`N E UR O M O D U L A T I O N F O R T R E A T I N G T H E O V E R A C T I V E B L A D D E R 7 2 5
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`obtained a success rate of 64% in a group of patients with
`idiopathic detrusor instability 2 years after treatment,
`while all patients with multiple sclerosis who initially had
`benefited from treatment relapsed within 2 months
`(although daily treatment of these patients at home
`was useful). Disappointing results have also been
`obtained in patients with spinal cord injury and elderly
`cognitively impaired nursing-home patients [24,25].
`Careful patient selection is crucial for good results and
`maximal electrical stimulation should not be used as a
`last resort [12]. However, failure of previous pharmaco-
`logical treatment does not exclude a good response
`beforehand [16,23].
`Treatment scheme and parameters. The intensity of
`stimulation should be as high as possible. Geirsson and
`Fall [12] noted that the results obtained with a routine
`outpatient procedure were far less good than those
`obtained in their prospective research series. They
`hypothesized that this was partly because the routine
`procedure was undertaken by a nurse with no doctor
`present; in the presence of a doctor, it is usually easier to
`persuade a patient to accept a high stimulation intensity.
`These authors also noted that the most successful results
`published were obtained in series using a stimulation
`frequency of < 20 Hz, while physiologically frequencies
`of 5–10 Hz are optimal in inhibiting the bladder. Possibly
`a higher frequency permits a higher stimulation inten-
`sity, as not every single pulse is detected. No data are
`available on the minimum number of
`treatments
`required. Primus and Kramer [23] found that some
`patients did not improve until the fifth treatment, and
`recommended treating patients at
`least 10 times.
`Intuitively,
`it may be expected that treatment on a
`daily basis will be more effective than weekly treatment;
`this hypothesis has not been tested. Siegel et al. [26]
`found no significant difference between daily and every-
`other-day treatment.
`Long-term effectiveness. Few studies reported success
`rates after a follow-up of >6 months; of the 17 patients
`treated by Yamanishi et al. [20], seven remained cured
`for at least 9 months on average after stimulation with
`no intervention, while another six achieved control with
`re-treatment. After a 2-year follow-up, 64% of 45
`patients with idiopathic detrusor instability [23] still
`reported subjective satisfaction; several needed re-treat-
`ment sessions and the remaining patients had relapsed.
`The success rate of 85% initially obtained by Eriksen et al.
`[16] in 48 women with idiopathic problems declined to
`77% after 1 year. Bratt et al. [27] traced these patients
`after 10 years; 27 were evaluable and symptoms of urge
`incontinence were reported by 78%. However, 30%
`leaked only once a week or less; 60% were satisfied with
`maximal electrical stimulation and would recommend it
`to a friend.
`
`# 2001 BJU International 87, 723–731
`
`Side-effects. No severe side-effects have been reported;
`local pain and diarrhoea disappear after a brief pause
`in therapy [18]. Mucosal irritation seldom occurs; the
`lesion quickly heals during a temporary break in
`the treatment [2].
`
`Transcutaneous electrical nerve stimulation
`
`TENS is used widely in the treatment of pain in a variety
`of conditions. Fall et al. [28] successfully treated patients
`with interstitial cystitis, using surface electrodes attached
`over the suprapubic area.
`the
`Technique.
`In treating the overactive bladder,
`electrodes are usually attached over the S2 and S3
`dermatomes
`(peri-anal
`region) or over
`the sacral
`foramina S2 and S3 (Fig. 2). Stimulation takes place
`for 20 min to several hours daily during one or more
`weeks. The intensity of stimulation should not exceed
`the level of discomfort.
`Evidence. Acute cystometric effects of TENS have been
`shown in patients with an unstable bladder [29,30]. The
`effects in patients with sensory urgency were uncertain;
`the bladder volume at first desire to void increased
`significantly with TENS over the suprapubic region, but
`not with TENS over the S2 to S3 sacral foramina. Bladder
`capacity did not respond at both sites in these patients
`[30]. However, of the patients treated by Walsh et al.
`[31], 76% and 60% reported an improvement in daytime
`frequency and urgency, respectively, while 56% noted a
`reduction of nocturia. Most of these patients had sensory
`urgency. Hasan et al. [29] found that urinary frequency
`
`Fig. 2. TENS in a child with electrodes stuck over the sacral
`foramina.
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`types of neuromodulation by its continuous
`other
`stimulation and close nerve contact, while the site of
`stimulation is closest to the spinal cord. A characteristic
`feature is the implantation of a pulse generator and an
`electrode stimulating one of the sacral nerves S3. These
`nerves have a higher representation in the bladder
`than the nerves S4 and cause less inconvenience to
`the legs than the nerves S2. Patients only undergo the
`implantation procedure if the preceding so-called PNE
`test was successful,
`i.e. only pre-selected patients are
`treated.
`Technique. To assess a patient’s suitability, a test
`electrode is placed percutaneously under local anaes-
`thesia, with the patient prone, in one of the S3 foramina
`and connected to an external pulse generator (Fig. 3a).
`The typical S3 muscle response, a bellows-like inward
`movement of the levator ani muscle and flexion of the
`great toe,
`is used to verify correct positioning of the
`electrode and proper functioning of the nerve. Stimu-
`lation is normally felt in the perineal area. After this
`acute PNE test the patient enters the subchronic test
`phase in which he or she completes a 3–7-day voiding-
`incontinence diary. Patients in whom the incontinence is
`
`a
`
`b
`
`72 6 J . G R O E N a n d J . L . H . R . BO S C H
`
`more than halved in 37% of 59 patients with an unstable
`bladder. The number of leakages also reduced by half in
`69% of those with urge incontinence. Good symptomatic
`results were also reported in a group of 55 children aged
`6–12 years [32]; 57% and 33% of those with daytime
`incontinence and bedwetting, respectively, became dry,
`while the voiding frequency became normal in 67%.
`Site of stimulation. Beneficial results of TENS at various
`sites have been reported [33], but few comparative
`studies have been undertaken. The possible sites of
`stimulation are:
`
`’ Sacral foramina S2 to S3.
`’ Sacral dermatomes S2 and S3 (peri-anal region).
`’ Dorsal penile or clitoral nerve.
`’ Suprapubic region.
`’ Thigh muscles (quadriceps muscles and hamstrings)
`[34].
`’ Common peroneal nerve.
`’ Posterior tibial nerve.
`
`The published results are conflicting; McGuire et al.
`[35] used traditional acupuncture points for inhibiting
`bladder activity over the common peroneal and posterior
`tibial nerve in the treatment of 15 patients with a
`neurogenic bladder dysfunction, and obtained good
`symptomatic results in most. However, Hasan et al.
`[29] reported a urodynamic improvement with TENS
`over the S2 and S3 dermatomes, but not with TENS over
`the posterior tibial nerve and the suprapubic region.
`Bower et al.
`[30] obtained comparable urodynamic
`results with TENS over the suprapubic region and the
`sacral foramina.
`Long-term results. The application of TENS is not useful
`if the patient is not offered the opportunity for re-
`treatment, either at
`the clinic or at home, as the
`therapeutic effects outlast the period of treatment only
`for a few months. The symptoms of 25 patients who were
`successfully treated by Walsh et al. [31] returned to
`pretreatment levels within 2 weeks in 40% of the patients
`and within 6 months in all; other authors obtained
`similar results [34,36].
`complications have been
`Side-effects. No major
`reported after using TENS. Local skin irritation at
`the site of the electrodes was seen in a third of the
`patients by Hasan et al. [29]. The use of hypo-allergic
`electrodes and limitation of the daily treatment period
`was helpful.
`
`Sacral nerve neuromodulation
`
`Sacral nerve neuromodulation (sacral nerve stimulation,
`SNS, InterStim therapy) has become established within a
`relatively short period. The method is distinguished from
`
`Fig. 3. a, Acute PNE test with a stimulation needle inserted
`through the left S3 foramen and placed parallel to the nerve S3.
`b, A pulse generator, extension cable and S3 foramen electrode
`with four stimulation points in a patient.
`
`# 2001 BJU International 87, 723–731
`
`Petitioner - Avation Medical, Inc.
`Ex. 1014, p. 726
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`N E UR O M O D U L A T I O N F O R T R E A T I N G T H E O V E R A C T I V E B L A D D E R 7 2 7
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`more than halved may receive the permanent implant,
`consisting of a foramen electrode fixed to the sacrum,
`an extension cable and a subcutaneously placed pulse
`generator (Fig. 3b).
`Evidence. The results in patients with an unstable
`bladder were recently summarized by Bosch [37];
`60–70% of patients respond to a test stimulation.
`Most studies in implanted patients showed a mean
`decrease in the grade of instability during cystometry.
`Symptomatically, about half of patients with urge
`incontinence and no neurogenic causes had >90%
`improvement in their incontinence, with 25% having a
`50–90% improvement and another 25% <50% improve-
`ment. The latter patients should be considered failures,
`because the results of
`the permanent
`implant are
`apparently worse than those of the test stimulation. As
`in other types of neuromodulation,
`the correlation
`between the urodynamic and the symptomatic improve-
`ment is only partial. In two comparative multicentre
`studies involving patients with refractory urge incon-
`tinence
`and urgency-frequency,
`respectively
`(not
`necessarily with urodynamically confirmed detrusor
`instability) half of the patients in whom the PNE test
`was successful were implanted [38,39]. Implantation
`was delayed for 6 months in the remaining patients, who
`received standard medical treatment and comprised the
`control group. The stimulation groups had significantly
`better symptomatic results than the control groups at
`6 months of follow-up.
`Suitable patients. At present, the only way to determine
`whether a patient is a candidate for implantation is a PNE
`test. Attempts to identify factors predicting the success of
`SNS failed [39,40]. On average, men do less well than
`women, probably because men have more severe grades
`of bladder overactivity than women before they become
`incontinent [37]. Psychological factors seem to play an
`important role [37,41]. A neurogenic cause of
`the
`bladder overactivity is no reason to exclude a patient
`from treatment; good results have been reported in
`patients with a variety of neurogenic lesions [42,43].
`Long-term effectiveness. In 45 patients with a mean
`follow-up of 47 months the cure rate decreased to < 80%
`and 65% after 1 and 1.5 years, respectively, but sub-
`sequently remained constant through the fifth year [44].
`The symptomatic results obtained at 6 months remained
`stable during a mean follow-up of 44 months in seven
`of nine women with neurogenic urge incontinence
`[43]. The symptoms return to the baseline level within
`a few days after discontinuing SNS [38,39].
`Side-effects and complications. The need to reposition the
`electrode after migration is the most frequently reported
`complication, occurring in < 20% of patients [39,44].
`Fracture of the electrode or the extension cable and
`technical problems with the pulse generator occasionally
`
`# 2001 BJU International 87, 723–731
`
`occur. A few patients complained of pain at the site of the
`pulse generator, which resolved after repositioning. Pain
`in the leg can be resolved by reducing the stimulation
`amplitude. Other complications are rare; nerve damage
`caused by continuous stimulation has not been reported
`[39,44].
`
`Current developments
`
`Two-stage implant. Displacement of the electrode during
`the PNE test may give a falsely negative result. Janknegt
`et al. [45] therefore repeated the test by placing a
`permanent electrode and an extension cable in patients
`in whom displacement was suspected, and connecting
`those to an external pulse generator. The permanent
`pulse generator was placed at a later stage if the patient
`had a good response (which was the case in eight of the
`10 patients). The current search for better test electrodes
`will hopefully reduce the need to perform extra surgical
`procedures [46].
`Bilateral stimulation and sacral laminectomy. Bilateral
`stimulation combined with a small sacral laminectomy
`to allow optimum electrode placement and fixation
`was first described by Hohenfellner et al. [47]. The
`value of the increased invasiveness of SNS remains to
`be determined.
`Buttock placement of the pulse generator. The pulse
`generator is traditionally placed in a lower abdominal
`pocket. Buttock placement has the advantage that the
`patient needs no repositioning during the operation and
`saves < 1 h of operative time [48].
`Conditional neuromodulation. Oliver et al. [49] found
`that neuromodulation applied only at moments of an
`increased level of urge suppressed this sensation. The
`usefulness of conditional neuromodulation in patients
`has still to be determined; it will extend the longevity of
`the pulse generator, which at present is 5–7 years.
`
`Percutaneous posterior tibial nerve stimulation
`
`Intuitively, the pelvic region is the most logical place to
`seek a site for neuromodulation, but physiological
`mechanisms permit suppression of bladder overactivity
`from a more distant location.
`Technique. A 34 G stainless steel or other thin needle is
`inserted 5 cm cephalad from the medial malleolus and
`just posterior to the margin of the tibia (Fig. 4). This point
`is known as the Sp-6 point in acupuncture. The needle is
`advanced to the medial edge of the fibula. A ground pad is
`usually attached to the medial surface of the calcaneous.
`Flexion of
`the great
`toe upon electrical stimulation
`indicates the correct positioning of the needle; a tingling
`sensation is often felt. Treatment usually takes place
`weekly for 10–12 weeks over 20–30 min.
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`72 8 J . G R O E N a n d J . L . H . R . BO S C H
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`Fig. 4. SANS with stimulation needle and ground pad.
`
`Evidence. McGuire et al. [35] used acupuncture points
`in TENS and obtained good symptomatic results; Chang
`[50] was the first to report results with the needle
`technique, showing statistically significant changes in
`the maximum cystometric capacity and maximum flow
`rate in a group of 26 women immediately after a 30-min
`treatment. Such changes were absent in a control group
`of 26 women. In addition, the proportion of patients who
`became stable and had subjective symptomatic improve-
`ment was greater in the treated group. Despite these
`promising results
`from the technique,
`it did not
`appear in urological practice until a commercial version
`(PercSANS@) became available recently. Most of the
`results of SANS to date are reported only in abstracts.
`Clinical success rates of 67–81% were reported during
`the ICS and EAU congresses of 1999 and 2000.
`Urodynamic results were reported by Klingler et al.
`[51], who found that bladder instability was eradicated
`in nine of 13 patients and improved in one. The bladder
`capacity increased significantly from a mean of 197 to
`252 mL.
`Long-term results. Stoller [52] described an 81% clinical
`success rate in 90 patients after a mean follow-up of
`5.1 years. Patients were treated continuously with
`increasing intervals between treatments; some patients
`treated themselves at home. These promising results
`were a reason to start the development of a minimally
`invasive peripheral implant device. No side-effects have
`been reported.
`
`Magnetic stimulation
`
`An electric current, e.g. through a coil, induces a mag-
`netic field, and a changing magnetic field in turn induces
`an electric field. These physical laws can be applied to
`stimulate the sacral roots or the pudendal nerves
`noninvasively using a magnetic field. This is possible
`because body tissues do not significantly attenuate such
`a field, but in contrast have a high electrical impedance.
`
`Fig. 5. Commercially available chair for magnetic stimulation.
`
`The advantage of magnetic stimulation over electrical
`stimulation is therefore that the stimulation intensity
`at the level of the nerves can be high [53]. Reports of
`magnetic stimulation in the context of the overactive
`bladder almost all originate from two groups.
`Technique. McFarlane et al. [54], who to date have
`applied magnetic stimulation for research purposes only,
`place a specially designed coil tangentially over the sacral
`skin and connect it to a stimulator. The muscle response
`of the toes (or the EMG response of the toe flexors to single
`pulses) is used for correct positioning of the coil. The
`optimal position is usually < 10 cm below the iliac crests
`and 5 cm lateral to the midline [54]; stimulation lasts for
`2–5 s. Yamanishi et al. [55] developed a chair with a coil
`and a cooling system in its seat; patients are instructed to
`sit so that the anus is positioned at the centre of the coil
`and so that the highest anal contraction is felt during
`stimulation (Fig. 5). Patients are treated twice a week
`for 5 weeks; one session lasts 15 min with cycles of
`60 s on/30 s off.
`Evidence. The group lead by Craggs was the first to
`show that magnetic stimulation of S3 acutely suppresses
`
`# 2001 BJU International 87, 723–731
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`Petitioner - Avation Medical, Inc.
`Ex. 1014, p. 728
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`N E UR O M O D U L A T I O N F O R T R E A T I N G T H E O V E R A C T I V E B L A D D E R 7 2 9
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`provoked unstable contractions in idiopathic and neuro-
`genic patients [54,56]. Stimulation also abolished the
`sensation of urgency. Yamanishi et al. [53] compared the
`acute cystometric effects of magnetic stimulation with
`those of anogenital electrical stimulation; the inhibition
`of detrusor overactivity was greater with magnetic
`stimulation. The same group of authors treated eight
`patients with urge incontinence, mainly neurogenic [55].
`The mean (SD) bladder volume at first desire to void and
`maximum cystometric capacity increased considerably
`from 160 (101) to 277 (52) mL, and from 211 (91) to
`336 (35) mL, respectively; the latter change was sig-
`nificant. Clinically, six patients were considered cured or
`improved. Daytime voiding frequency and the number of
`daytime leakages significantly decreased from 9.5 (2.8)
`to 8.1 (3.5), and from 3.1 (3.1) to 1.5 (1.2), respectively.
`Long-term effectiveness. No data on patients with pure
`urge incontinence are available. Sand et al. [57] treated
`76 women with mixed incontinence; considering only
`those women with no identified risk factors, 11 of 16 had
`a >50% improvement in the number of incontinence
`episodes per day at 2 weeks after therapy, while eight of
`14 did so at 18 weeks.
`Side-effects. Magnetic stimulation normally causes no
`serious discomfort; there were two idiopathic patients
`who found stimulation painful or uncomfortable, while
`a neurogenic patient had an uncontrolled bowel
`evacuation [54,56].
`
`Intravesical transurethral electrostimulation
`
`Intravesical electrical stimulation is based on direct
`activation of receptors in the bladder and aims to enable
`the patients to recognise urge; it cannot be considered
`a kind of neuromodulation. However, the method so
`closely resembles most neuromodulation techniques that
`a brief description is appropriate.
`Technique. A special catheter equipped with a stimula-
`tion electrode in its tip is inserted transurethrally into the
`bladder, which is partially filled with saline, a conducting
`fluid. A ground pad is placed on an arm or leg. One port
`of the catheter is connected to a pressure monitor, so
`that the patient can correlate their sensations with
`the behaviour of the bladder (biofeedback). Treatment
`usually takes place five times per week for 3 weeks, with
`one session taking 60–90 min.
`introduced
`Evidence.
`Intravesical
`stimulation was
`several decades ago with the aim of improving bladder
`sensation and bladder emptying in patients with a
`neurogenic bladder, especially children. It follows from
`this aim that only patients in whom at least some neural
`pathways between the bladder and the cerebral centres
`are preserved are suitable candidates. The method is still
`used in these patients, but it is controversial [58,59].
`
`# 2001 BJU International 87, 723–731
`
`Application of the method in patients with an overactive
`bladder is relatively new. The rationale is that these
`patients may learn to recognize involuntary contractions
`and inhibit them by squeezing the pelvic floor. Risi et al.
`[60] treated 162 patients, reporting an improvement in
`urinary continence in 25 of 33 with myelomeningocele,
`but the treatment failed in 75% of the remaining patients.
`The authors
`therefore advised against
`intravesical
`electrostimulation in idiopathic cases.
`
`Conclusions
`
`Neuromodulation is a valuable treatment option for
`patients with an overactive bladder. The non-surgical
`techniques can be applied as an alternative to standard
`conservative treatment, or may be tried if such a
`treatment
`fails. Sacral neuromodulation should be
`considered before using a more invasive operation such
`as bladder augmentation. It is unclear to what extent
`the various techniques are interchangeable,
`i.e.
`it is
`unknown whether a technique that is or is not effective
`in a patient can be successfully replaced by another
`technique, because no variables predictive of success
`have been identified. The determination of reliable
`selection criteria would be a major advance; a better
`understanding of
`the mechanism of action might
`contribute considerably to this goal.
`
`References
`
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