Sacral Neuromodulation Beyond Pelvic Pain!!!

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1 Sacral Neuromodulation Beyond Pelvic Pain!!! Dr. Hirachand S Mutagi. Senior Consultant Pain Physician. Head -Sakra World Hospital. Director ReLeaf Pain Services. Rapid advances in neurostimulation therapy and an evidence base in neurostimulation therapy for neuropathic pain have fuelled evolution in expertise among pain physicians. Sacral neuromodulation is effective ammunition in the hands of pain physicians in carefully selected patients with persistent pelvic pain. As the utility of sacral neuromodulation expands in the field of bladder and bowel dysfunction, a pain physician expertise has the potential for contributing significantly in multidisciplinary teams beyond the traditional playing field of pain physicians. The sacral neuromodulation system (SNS) (fig 1) involves electrical stimulation of the sacral nerves by an implantable stimulating electrode on sacral nerve, which is then powered by an implanted implantable pulse generator(ipg). The electrical stimulation modulates the sacral nerve roots that supply the bladder, bowels, urinary and anal sphincters, and pelvic floor muscles. The intensity, frequency, and other stimulation characteristics can be altered by the external programmer to optimise and regulate the stimulation to achieve the desired clinical effect. Figure 1: Schematic image of posterior pelvis with SNS lead in S3 foramen connected to an implantable pulse generator (IPG)

2 Enthusiasts of neuromodulation in pain medicine are well aware of pelvic pain syndromes called by various nomenclatures inclusive of interstitial cystitis, pelvic neuropathic pain, pudendal neuralgia, and proctalgia fugax. The therapy has rewarding outcomes in nonpainful conditions as well. Indications: Refractory clinical states that have not responded to conventional medical or physical therapy is the basic pre-requisite requirement to consider SNS therapy in the following conditions chronic urinary retention (non-obstructive)- Meticulous attention to ensure ruling out obstructive pathology is essential. The following diagnosis have been proposed Fowler's syndrome, spastic pelvic floor syndrome and bladder hypo/acontractility. Overactive bladder syndrome (functional Urinary voiding dysfunction)- OAB syndrome is characterized by urgency, with or without urge incontinence in the absence of local or metabolic factors explaining these symptoms. Sacral neuromodulation is an appealing therapeutic modality for symptoms refractory to conventional pharmacotherapy, and is relevant for both neurologic and nonneurologic causes. Bowel dysfunction incontinence (chronic constipation debateable indication often proximal gut dysfunction) Chronic pelvic pain syndromes (interstitial cystitis, pelvic neuropathic pain, pudendal neuralgia, and proctalgia fugax) Contraindications: An identifiable cause for the visceral / urogenital symptoms makes neuromodulation an inappropriate therapy, unless there is no remedial curative therapy for the condition. Mechanical outlet obstruction (urinary or faecal) No evidence of infection, psychosocial stressors A diagnosis requiring frequent MRI surveillance Inadequate response to test sacral nerve stimulation Patient s inability to manage a sophisticated device Sacral nerve stimulation technique: A meticulously selected patients with the right indication commonly undergoes a trail stimulation (test phase) of varying duration (days to few weeks). A satisfactory outcome in the test phase provided therapy sample to identify responders while patient experiences the therapy to determine if long-term therapy is a fruitful and viable option. Test stimulation (SNS trial):

3 Temporary trial lead (single contact) is placed percutaneously as a day-care / OPD procedure and the electrode is powered by an external stimulator power source. Best therapeutic results are achieved by electrode placement in the S3 foramen. The best stimulation pattern and appropriate lead placement is confirmed by plantar flexion of great toe and bellows like elevation of whole perineum (pelvic floor cranial elevation), tingling sensation in whole perineum. Secure dressing hold the lead in place during the trial stimulation lasting a variable duration based on pattern of patients symptoms, comfort level of patient, aseptic lead insertion site, infrastructure and setup of the implanting unit. The trial stimulation period involves monitoring and adjusting the external pulse generator to identify the optimal comfort level of stimulation and to evaluate therapy. The trial period is completed with removing the trial lead. Permanent Implantation of SNS: A successful trial of SNS therapy via a temporary trial lead is followed by permanent implantation of SNS. This involves a fluoroscopy guided percutaneous placement of a SNS tined lead (fig 2) in S3 foramen. The tined lead has 4 electrode contact points and hence more reliable in achieving nerve stimulation in comparison to the test lead. The tines on the lead as self anchoring outward projections on the lead to hold it in place / minimise migration. The lead is additionally anchored to the lumbosacral fascia through a small incision and subcutaneous dissection. The lead is then connected to the implantable pulse generator (IPG) that is implanted in a subcutaneous pocket usually in the superolateral quadrant of the buttock or iliac fossa abdominal wall. Figure 2: Special leads designed to anchor lead in the S3 Sacral foramen. Post implantation programming of the SNS system ensures optimal therapy to achieve sub perceptive / perceptive paresthesia in the perineum avoiding associated motor stimulation. This is achieved telemetrically with an external remote programmer.

4 Outcomes: SNS for pelvic pain: The use of SNM for pain related to PBS/IC has generally been done for patients with pain related to painful bladder syndromes that have failed multiple previous treatments. Lone provides evidence of some benefit from SNM in terms of reduced pain scores along with improvements in frequency and bladder volume in patients with pain related to PBS/IC. The case series/case reports also report broadly similar findings to the RCT. Benefits of SNM for pain were reported at follow-up to 7 years after implantation. 1 SNS for Overactive bladder: SN has become an increasingly utilized option for refractory OAB symptoms. Over the past two decades, SN has continued to gain popularity to relieve refractory OAB symptoms with studies demonstrating that it is an effective treatment with potentially long-term enduring benefits. However, these benefits have been shown to come at the expense of a high rate of adverse events although with comparable (slightly favourable) long-term cost-effectiveness to botulinum toxin A with higher initial cost. 2 SNS for faecal incontinence: In the two parallel group trials, 53 and 15 participants with faecal incontinence who were in the SNS group experienced fewer episodes of faecal incontinence compared to the control group at 3 and 12 months. In the first crossover trial, 24 participants who completed the trial chose the period of stimulation they had preferred while still unaware whether this was on or off. Nineteen participants who preferred the on period experienced 59% fewer episodes of FI per week during the on period, and 5 participants who preferred the off period experienced 118% more episodes of FI per week. In the second crossover trial, the participants did not experience episodes of FI during either the on or the off periods. In the third trial, participants experienced 83% fewer episodes of faecal incontinence during the on compared with the off period. In the fourth crossover trial participants experienced 88% fewer episodes of faecal incontinence during the on period compared with the off period. 3 SNS for constipation: In one trial assessing SNS for constipation, two participants reported an increase of 150% in the frequency of passing stools per week, and time with abdominal pain and swelling went down from 79% during the off period to 33% during the on period. However, in the much larger second trial assessing SNS for constipation, in 59 participants SNS did not improve frequency of bowel movements. 3 SNS adverse events: Out of the studies reviewed, there was generally a 30% 40% rate of complications within the first 5 years. This has a substantial impact on the patients when the cost of a revision of removal surgery potentially combined with the need to implant a new device.2 Summary: Sacral neuromodulation ahs an evolving list of indications beyond pelvic pain syndromes. A definite role for carefully selected patients especially in overactive bladder syndrome and non-obstructive urinary retention. The expensive therapy is cost effective at 5 years. This

5 presents an opportunity for pain physicians to collaborate n multidisciplinary teams delivering sacral neuromodulation. References: 1 Srivastava D. Efficacy of sacral neuromodulation in treating chronic pain related to painful bladder syndrome/interstitial cystitis in adults. J Anaesthesiol Clin Pharmacol 2012;28: Sukhu T, Kennelly MJ,Kurpad R. Sacral neuromodulation in overactive bladder: a review and current perspectives. Research and Reports in Urology 2016:8; Thaha MA, Abukar AA, Thin AN, Ramsanahie A, Knowles CH. Sacral nerve stimulation for faecal incontinence and constipation in adults. Cochrane Database of Systematic Reviews. 2015, Issue 8.