Neuromodulation of the sacral nerves has been introduced gradually from 1994 onwards and when Medtronic commercialised the Interstim devices. The introduction of the tined lead proved to be a major step in reducing the number of reinterventions.
Since then, sacral nerve stimulation (SNS) has been used for several functional urological problems. For many urologists up to now it remains an enigmatic treatment option that both deals with the overactive bladder problems and retention problems. This apparent contradiction can only be understood by looking at the afferent and efferent innervation of the bladder and pelvic floor.
In recent years the role of afferent input into the central nervous system has been studied in some detail, showing that the higher brain centres, brainstem centres and centres located in the spinal cord all play an important role in the control of the bladder filling and emptying cycle. Functional urologists have learned to look at the bladder and sphincter from an electrician’s point of view, rather than a plumbers point of view. The exact working mechanism, however, remains unknown, but it is clear that the stimulation alters the afferent input into the central nervous system (CNS) and the processing of these signals, resulting in a better coordination between the different centres. Despite the fact that SNS is available for many years, it’s acceptance in the urological community is still limited.
There are many reasons for this phenomenon, such as: the price of the device, the type of surgery that is out of normal range of surgical skills, the lack of expensive marketing strategies by the companies, the lack of an accepted mode of action, and the high reoperation rate, among others. But when examining the facts, it is reasonable to reconsider and perhaps change one’s point of view.
SNS for overactive bladder SNS is recommended by the ICI 2009 as treatment for idiopathic OAB that became refractory to anticholinergic treatment (grade A). Also botulinum toxin is recommended for this indication (grade C). A recent systematic review, however, showed that only seven good quality studies were available and that some authors reported results from the same study cohort.
These studies reported only on 345 individual patients over a time span of eight years? Most of these studies are case series. The efficacy of the treatment in women seems to be good. There are little data on men. Using tined leads the surgical revision rate was 3-16%. 6% of patients were explanted because of loss of efficacy and 5-11% were explanted for infectious complications.
These revision and explants rates are much lower since the introduction of the tined lead. The challenge for the clinician who is confronted with refractory OAB now consists in choosing the right treatment: botulinum toxin or SNS. At this moment there are no good comparative data. Cost-comparison studies only answer part of the question.
Does every refractory OAB patient respond in the same way to both treatment options or is one treatment better than the other for some patients? SNS has proven long-term effects, while botulinum toxin needs to be injected regularly. Many questions remain. SNS for neurogenic bladder While some authors report their initial experience with SNS in neurogenic indications such Parkinson’s disease, incomplete spinal cord lesion, cerebrovascular accidents and others, the general consensus is that the use of SNS in these indications remains experimental.
A recent study by Sievert et al. opens a new field of research. This group used SNS very early after spinal cord injury. By implanting the stimulator they could prevent the occurrence of neurogenic detrusor overactivity.
This clinical observation challenges our current understanding of the pathophysiology neurogenic detrusor overactivity as a consequence of C-fibre activation. The role of electrical stimulation on this process deserves further study. SNS for urinary retention Urinary retention in women is one of the most robust indications for SNS.
Besides intermittent catheterisation, no other treatment has been proven to be beneficial for this condition. The presence of Fowler’s syndrome seems a predictor of long-term success with SNS.
SNS for BPS/IC Bladder pain syndrome and interstitial cystitis are difficult to manage. Recognising the difficulties in correctly diagnosing these conditions, several authors report on the use of SNS of this indication. Gajewski et al. noted that the presence of urgency was a positive predictor for success. The explant rate in their group of 46 patients was 28%. 23 patients had a >75% improvement of their complaints.
Powell et al. showed in their series of 22 patients that urgency improved in 77%, frequency in 77% and pelvic pain in 65%.
A recommended treatment SNS is a recommended treatment for refractory idiopathic OAB and urinary retention in women. There are little data on men. The positioning of this treatment versus botulinum toxin must be studied further. The quality of the data on alternative indications such as neurogenic detrusor overactivity and painful bladder syndromes is still insufficient to come up with any conclusion. Thus, there is still a need for high quality studies in this field.
Full version of this article, accompanied by references was published in the latest issue of EUT. This article was prepared by the EAU Section of Female and Reconstructive Urology (ESFFU)
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