*2.2.2.3 Contraindications*

Authorities have agreed on certain absolute and relative contraindications for SNM [4], with exceptions and points up for debate to date in the literature. Absolute contraindications of SNM are:


The *relative contraindications* for SNM therapy, as outlined by many guidelines including the ICS best practice statements, do not preclude use of SNM, but must be vigilantly observed and discussed with the patient prior to embarking on treatment. These include:


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other [36].

*Neuromodulation in Urology: Current Trends and Future Applications*

4.Abnormal sacral anatomy is a sensible contraindication in which such deformities would hinder the identification of the correct sacral foramens required for

With the exception of head MRI examination, the ongoing or anticipated need for MRI examination for patients is a relative contraindication for SNM implantation [4, 32]. The potential effect of non-head MRI examinations on an implantable metallic device such as SNM have debilitated practitioners and potential patients alike with one series reporting that 23% of device explantations at their center were due to the need of the patient to undergo this examination. This has absurd financial and clinical implications in the face of an effective

In the same series, two thirds of the explanted patients required a change in management post-explantation, including intradetrusor botulinum injections, or to resort to self-intermittent urinary catheterization or even require in one case cystectomy and urinary diversion. Thus, explantation has dire consequences that must be outweighed against the potential need and risks of undergoing MRI especially when over 20% of the patients that were explanted prior to MRI examination ended up not undergoing the imaging test and just over 50% of those MRI results influenced non-genitourinary treatment decision making [33]. Additionally, one cannot help but wonder the number of patients who may have benefitted from SNM therapy had they not been excluded due to prospective need for MRI with better

It is difficult to design trials to test for the effects of SNM, or any form of neuromodulation or therapy for that matter, when there is a hypothesis of potential teratogenic effect on the fetus, or risk of abortion or premature delivery. Apart from the overridden potential for damage to the SNM system when it was historically being implanted in the anterior abdominal wall, completely posterior SNM implants or their predecessors have not been shown in a number of series and reviews to be associated with any fetal malformations or early deliveries or a higher rate of cesarean sections. These reports are based on pregnant women who against recommendation and electively opted to maintain their SNM devices on during their pregnancies fully or at certain periods and trimesters [34, 35]. Thus, the decision to continue neuromodulation, or to proceed with implantation for a woman who has not completed her family or is actively trying to conceive, remains a debatable and individualized decision, but in accordance with manufacturer recommendations and societal guidelines and until more compelling evidence arises, pregnancy will remain a contraindication for SNM, though more relatedly

Potential interference of SNM devices with other implantable electrostimulators such as cardiac pacemakers has long been speculated. A series of three patients who have cardiac pacemakers and underwent SNM implantation has reported that no interference was observed on the part of either of the implanted devices by the

*DOI: http://dx.doi.org/10.5772/intechopen.92287*

optimum effect and implantation.

*2.2.2.4 Magnetic resonance imaging*

implantation [33].

and alternative planning.

relevant than absolute [34].

*2.2.2.6 Other considerations*

*2.2.2.5 Pregnancy*

4.Abnormal sacral anatomy is a sensible contraindication in which such deformities would hinder the identification of the correct sacral foramens required for optimum effect and implantation.

### *2.2.2.4 Magnetic resonance imaging*

*Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

Although the FDA has not recognized or approved these applications of SNM, there is a growing body of evidence that demonstrates its effectiveness in other genitourinary pathological conditions. In particular are chronic pelvic pain disorders including both IC/BPS and non-IC chronic pelvic pain syndrome (CPPS). Despite lack of availability of high-level evidence, the off-label application of SNM in these conditions continues with variable results in improving associated urinary symp-

Other non-approved applications of SNM include its use in special populations such as those with neurogenic lower urinary tract symptoms, pediatrics and adolescents, and even in contraindicated situations including continued SNM in pregnancy for women with urological conditions. Most of these applications carry hypothetical risks, a spectrum of which have been refuted in small case series and reports in literature, but bigger studies are needed to elucidate and clarify the role

Authorities have agreed on certain absolute and relative contraindications for

1.An inadequate clinical response—this is dictated by the universally accepted cut-off of more than 50% improvement during the test phase of SNM.

2.The patient's inability to operate the SNM device, or lack of caregiver support

3.Pregnancy, and this remains a point of debate across literature, as will be

The *relative contraindications* for SNM therapy, as outlined by many guidelines including the ICS best practice statements, do not preclude use of SNM, but must be vigilantly observed and discussed with the patient prior to embarking on treatment.

1.Severe and/or rapidly progressive neurologic disease with urinary symptoms in such a state, the patient's foreseeable benefit from treatment, even based on a successful test phase, would be challenged by the changing neurological

2.Complete SCI, which would hinder the modulatory effect of SNM in higher

3.The ongoing recognized or observed need for magnetic resonance imaging (MRI) examination, particularly in patients with established neurological disorders like multiple sclerosis (MS) that may need continued MRI assessment or patients undergoing work-up for other conditions that may need it, particularly non-head MRI examination, which will be discussed further in a separate segment as growing reports continue to argue MRI safety with

status or development and progression of the disease.

SNM [4], with exceptions and points up for debate to date in the literature.

*2.2.2.2 Off-label uses*

toms and quality of life parameters.

Absolute contraindications of SNM are:

thereof who could assist in doing so.

nervous centers as discussed earlier.

implanted SNM devices.

discussed further next.

These include:

of SNM in these situations.

*2.2.2.3 Contraindications*

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With the exception of head MRI examination, the ongoing or anticipated need for MRI examination for patients is a relative contraindication for SNM implantation [4, 32]. The potential effect of non-head MRI examinations on an implantable metallic device such as SNM have debilitated practitioners and potential patients alike with one series reporting that 23% of device explantations at their center were due to the need of the patient to undergo this examination. This has absurd financial and clinical implications in the face of an effective implantation [33].

In the same series, two thirds of the explanted patients required a change in management post-explantation, including intradetrusor botulinum injections, or to resort to self-intermittent urinary catheterization or even require in one case cystectomy and urinary diversion. Thus, explantation has dire consequences that must be outweighed against the potential need and risks of undergoing MRI especially when over 20% of the patients that were explanted prior to MRI examination ended up not undergoing the imaging test and just over 50% of those MRI results influenced non-genitourinary treatment decision making [33]. Additionally, one cannot help but wonder the number of patients who may have benefitted from SNM therapy had they not been excluded due to prospective need for MRI with better and alternative planning.

### *2.2.2.5 Pregnancy*

It is difficult to design trials to test for the effects of SNM, or any form of neuromodulation or therapy for that matter, when there is a hypothesis of potential teratogenic effect on the fetus, or risk of abortion or premature delivery. Apart from the overridden potential for damage to the SNM system when it was historically being implanted in the anterior abdominal wall, completely posterior SNM implants or their predecessors have not been shown in a number of series and reviews to be associated with any fetal malformations or early deliveries or a higher rate of cesarean sections. These reports are based on pregnant women who against recommendation and electively opted to maintain their SNM devices on during their pregnancies fully or at certain periods and trimesters [34, 35].

Thus, the decision to continue neuromodulation, or to proceed with implantation for a woman who has not completed her family or is actively trying to conceive, remains a debatable and individualized decision, but in accordance with manufacturer recommendations and societal guidelines and until more compelling evidence arises, pregnancy will remain a contraindication for SNM, though more relatedly relevant than absolute [34].

### *2.2.2.6 Other considerations*

Potential interference of SNM devices with other implantable electrostimulators such as cardiac pacemakers has long been speculated. A series of three patients who have cardiac pacemakers and underwent SNM implantation has reported that no interference was observed on the part of either of the implanted devices by the other [36].

### *2.2.3 Predictors of effect*

One of the hallmarks of diagnosis of urinary and voiding dysfunction disorders is the utility of urodynamic testing (UDS). Of different types and modes, this diagnostic test aims at reproducing patient symptoms and correlating them to net intradetrusor pressure, among other parameters, in simulated bladder filling and voiding phases. Much has been disputed about the need for UDS testing to diagnose straightforward and clinically apparent conditions such as overactive bladder, and whether UDS findings could help predict outcomes of therapy including SNM prior to its implantation. However, evidence suggests that no single UDS parameter or finding can predict SNM success [37].

In its best practice statement, the ICS did not find sufficient evidence to support that urodynamic studies can predict outcomes of treatment for SNM, while it supported based on higher level of evidence a stronger recommendation for performing SNM trial phases as the "single most valuable tool" to predict outcome of SNM [4].

Attention has been given to difference in SNM effects between certain patient populations. Gender differences have been long hypothesized, with attention focusing on SNM effects on pelvic floor rehabilitation and its close relatedness to urinary and chronic pelvic disorders in females as a potential modality of effect. In a matched pair analysis, a group of researchers reported on 80 patients who received SNM implants for urge urinary incontinence and found that more women tended to receive implants than men. While urinary frequency and symptom scores improved in both groups, over 3 years, the number of urge incontinence episodes per day improved in men more than women, while the severity of the incontinence improved in women more than men [38]. This gender discrepancy may be explained in part by SNM effect, but perhaps is also due to anatomical difference of the distal urinary tract in men and women.

Another patient population suspected to be at a lesser advantage from SNM efficacy are older patients and those with certain comorbidities such as obesity. Interestingly, one study did not only find no difference in response among older patients but further identified that age correlated with a lower rate of surgical revisions of the implantation—3% lower odds per year. In the same study, BMI did not influence explantation rates [39].

It is undeniable that there are identifiable structural changes in the bladder muscle and wall that incur from long standing overactive bladder and non-obstructive urinary retention, and hypotheses suggest this may affect the therapeutic outcomes of SNM as the symptom duration increases. However, even symptoms extending for more than 10 years have not been shown to have any significant effect on the success of SNM [40].

### *2.2.4 Results of SNM and its efficacy*

SNM has proven an efficacious modality of treatment of different genitourinary disorders, with durable success rates between 70 to 80% in certain conditions such as refractory OAB [11, 31, 41, 42]. In one survey of SNM patients, satisfaction rates were reported to be over 95% with SNM therapy and were not affected by patient age or any complications or program type, a testament to the efficacy of this treatment [43]. The multitude of data in the literature also attests to the general safety of SNM [44].

History of prior back surgery may be deemed a challenging patient condition for SNM implantation, but a review of 500 patients has shown that such a history did not negatively affect SNM outcomes [45]. Even in patients with prior anti-incontinence

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*Neuromodulation in Urology: Current Trends and Future Applications*

of SNM, however, these remain generally good and acceptable [46].

surgery and history of pelvic organ prolapse surgery, the efficacy of SNM has been established. Surgeries of the bladder and pelvic floor may slightly affect the outcomes

The debate continues on what is the cost-effectiveness of SNM compared to other available treatments for refractory voiding conditions be it OAB or UUI or others. These include in general combination medication, intradetrusor botulinum injections (repeated as the effect of one injection wears out necessitating periodic repeat injections), and more definite bladder or anti-incontinence surgeries. The long term outcomes of SNM compared to the need for maximal medical therapy or repeated botulinum injections poses a cost-effective benefit superior to the aforementioned counterparts, with some authors even arguing that from a patient's perspective it may well be considered an appropriate primary therapy rather than a second or third line alternative [47]. Compared to botulinum injections in particular, SNM was shown in one study to be cost-effective from the third year of application onwards, with a clear dominance should treatment be continued for 10 years [48]. However, results from the ROSETTA randomized trial which compared SNM and botulinum bladder injections for refractory UUI showed SNM

Perhaps the arguments for and against the cost-effectiveness of SNM versus other treatments lay not just in the treatments it is being compared to but in terms of what condition these treatments are being utilized for. In a focus article on safety and cost of SNM compared to botulinum injections for OAB, although SNM was costlier, it was safer than intradetrusor botulinum injections. The latter carries a substantial side effect profile including urinary tract infections, hematuria, urinary retention, and more frequent emergency room visits, all not common occurrences,

As with any surgical procedure, preoperative assessment and counseling are of paramount importance. It has been identified that such counseling should include discussions on possible expected side effects and adverse events of SNM therapy, such as implant site pain, infection, paresthesia, and leg and buttock pain. Moreover, the patient must understand that within the spectrum of approved devices in clinical practice, currently the Interstim® device in its two generations, there may arise a need for surgical revision of the implant or ongoing reprogramming atop an eminent and eventual need for replacement of the implantable pulse generator (IPG) once the battery wears out should treatment extend beyond an expected life-expectancy of 3 to 5 years on average. Additionally, and based on ICS recommendations, urodynamic testing is not mandatory, but phase testing is highly recommended prior to embarking on surgical implantation of the SNM IPG [4, 51]. One side effect profile that has been raised in the literature has been the psychological aspects of SNM therapy, though some authors have argued that a reverse pathology is possible with patients with chronic genitourinary and pelvic pain disorders who are potential candidates for SNM are pre-operatively burdened or have pre-existing psychological ailments. As is the limited evidence from some case reports and series, some patients encounter behavioral changes or exacerbation of preexisting psychological conditions such as depression, which has led to the argument of need for psychological assessment of certain traits that may affect SNM outcomes [52]. However, this has yet to be reflected in the guidelines and societal recommendations

*DOI: http://dx.doi.org/10.5772/intechopen.92287*

as a less cost-effective alternative [49].

but may tip the scale in favor of SNM [50].

*2.2.6 Preoperative assessment and counseling*

*2.2.5 Cost-effectiveness*

surgery and history of pelvic organ prolapse surgery, the efficacy of SNM has been established. Surgeries of the bladder and pelvic floor may slightly affect the outcomes of SNM, however, these remain generally good and acceptable [46].
