Future indications for sacral nerve stimulation

Chronic Sacral Nerve Stimulation Inhibits Visceral Hypersensitivity in Diarrhea-Predominant Irritable Bowel Syndrome Rats Model

OBJECTIVE

Sacral nerve stimulation (SNS) is emerging as a novel treatment for irritable bowel syndrome (IBS). However, its effects are limited, and the underlying mechanisms remain largely unknown.

MATERIALS AND METHODS

In this study, rats were divided into three groups (n = 12 rats per group): 1) the SNS group; 2) the sham SNS group (the sham group for short); and 3) the control group. The SNS and sham groups were exposed to chronic and acute stress to establish an IBS model. Electrode implantation surgery was performed in rats with the IBS model. The SNS group received electrical stimulation for 30 minutes every day for seven days. Abdominal withdrawal reflex (AWR) was used to evaluate the effect of SNS on visceral sensitivity in diarrhea-predominant IBS (IBS-D) rats. The frequency domain of heart rate variability (HRV) was analyzed to assess the effect of SNS on regulating the autonomic function. The expression of transient receptor potential vanilloid 1 (TRPV1) in the colon, spinal cord, and hippocampus was detected by immunohistochemistry to explore the mechanism of SNS in IBS-D rats.

RESULTS

Compared with the sham group, AWR scores were significantly decreased under different gas volumes of stimulation of 0.4, 0.6, and 0.8 ml for rectal distention in the SNS group (all p < 0.05). However, there was no significant difference <1.0 ml between the two groups (p > 0.05). Compared with the sham group, the frequency domain indexes of HRV were significantly altered. Normalized low-frequency power and low frequency-to-high frequency ratio were significantly decreased, and normalized high-frequency power was significantly increased in the SNS group (all p < 0.05). Moreover, the expression of TRPV1 in the spinal cord and colon in the SNS group was significantly decreased compared with the sham group (both p < 0.05). These results suggested that chronic SNS not only improved the visceral sensitivity and autonomic dysfunction but also decreased the expression of TRPV1 in the spinal cord-gut tissue in IBS-D rats.

CONCLUSION

Chronic SNS was found to have an inhibitory effect on visceral hypersensitivity in IBS-D rats, providing experimental evidence for its potential clinical application in IBS.

Patterns of tined lead migration in sacral nerve modulation

AIM

Lead migration is a common cause of loss of efficacy in sacral nerve modulation. Our aim was to systematically study the migration pattern of tined leads in sacral nerve modulation. Our hypothesis was that tined leads may promote forward migration because of their configuration.

METHOD

Consecutive patients treated with sacral nerve modulation with a tined lead electrode, who had experienced loss of efficacy and had radiographs both at baseline and after loss of efficacy between 2005 and 2016 were eligible for inclusion.

RESULTS

Twenty-five patients out of 70 with loss of efficacy were studied. Lead migration was measured as percent electrode movement in relation to sacral cortex at lateral projection. All had some degree of lead migration, ranging from 35% backward to 74% forward migration. Sixteen (64%) had forward migration while nine (36%) had backward migration. In seven patients (28%), loss of efficacy was associated with an episode of perceived mechanical strain on the electrode. Fifty percent (4/8) who associated their loss of efficacy with an adverse event had forward migration of the electrode.

CONCLUSIONS

Forward lead migration with concomitant loss of efficacy seems to be a common event in patients with tined leads, hence supporting our hypothesis. The retrospective design and that some of the patients with loss of efficacy could not be included because of incomplete data, which is a limitation to the study. Further studies are needed to confirm to what extent the direction and magnitude of the migration relate to loss of efficacy.

Overactive Bladder Syndrome Treatments and Their Effect on Female Sexual Function: A Review

Introduction

Overactive bladder (OAB), the most common subtype of urinary incontinence, has a heavy price on quality of life, especially on sexual life. Unfortunately, most women rarely voice the worsening of sexual function, especially those who already suffer from OAB symptoms. It has been demonstrated that patients who suffer from OAB score lower on Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire and Female Sexual Function Index scores, meaning that their sexual function is debilitated. Therapies for OAB begin with traditional pelvic floor physiotherapy, advance to anticholinergic drugs, and become more invasive with intravesical injections of onabotulinumtoxinA (commonly known as Botox). Last, for patients resistant to conservative therapies, sacral neuromodulation is the treatment of choice.

Methods

This article reviews the current literature that sheds light on the above 4 treatments and their effect on sexual function. This topic is of great importance because of the under-reporting of sexual dysfunction in women who suffer from OAB, in hopes of raising awareness of sexual function for clinicians treating patients with OAB.

Results

This review found that the aforementioned 4 treatments for OAB (physiotherapy, anticholinergic drugs, intravesical injections of onabotulinumtoxinA, and sacral neuromodulation) do not have a detrimental affect on sexual function. On the contrary, the little data that do exist show that sexual function increases after these therapies are completed in women with OAB.

Conclusion

This review concludes with a positive outlook: physicians are helping women with OAB syndrome to improve their sexual function. However, not enough data exist, partially due to under-reporting of diminished sexual function.

Levy G, Lowenstein L. Overactive Bladder Syndrome Treatments and Their Effect on Female Sexual Function: A Review. Sex Med 2019;8:1–7.

Treatment Outcome of Acute Sacral Nerve Stimulation in Functional Anorectal Pain

BACKGROUND

Sacral nerve stimulation (SNS) has revolutionized the management of certain intractable cases of fecal and urinary incontinence; however, the management of functional anorectal pain (FAP) has been addressed in only a few studies.

OBJECTIVE

The aim of this study was to evaluate the treatment effect of SNS in improving FAP symptoms.

METHODS

A total of 120 patients with FAP who had undergone temporary SNS probe placement were investigated at Qianfoshan Hospital between January 2014 and December 2016. Pre- and post-SNS treatment outcomes were assessed using the VAS, anorectal manometry, and the 36-item short-form health survey (SF-36) medical outcomes study instrument.

RESULTS

A total of 120 patients proceeded to insertion of an SNS probe at the S3 nerve root (2 Hz, 1.50 mA, 0.10 milliseconds). Of these, 75 patients were cured, 41 improved, and 4 had an ineffective outcome. The total effectiveness rate was 96.7% 1 year after treatment. There was a significant reduction in the median VAS score pre-SNS and post-SNS, from 8 to 3, respectively. Patients post-SNS had lower anal maximum contraction pressure and anal rest pressure than did patients pre-SNS. Compared with the pretreatment group, there were no substantial differences between anal longest contraction time and rectal rest pressure. In addition to general health, there was a substantial improvement in the remaining dimension scores of the SF-36.

CONCLUSION

The effect of SNS in treating FAP was positive, and the improvement of symptoms was substantial and worthy of clinical promotion.

Sacral neuromodulation and female sexuality

INTRODUCTION AND HYPOTHESIS

An up-to-date review of the impact of a permanent sacral neuromodulation (SNM) implant (Medtronic, Minneapolis, Minnesota, USA) on female sexual function (FSF).

METHODS

Clinical studies published from January 2001 to February 2014 evaluating the impact and/or safety of permanent SNM on FSF were reviewed.

RESULTS

Nine studies were selected that investigated the impact on sexual response when the aim of the SNM was to resolve urinary symptoms mainly due to overactive bladder (seven studies) or faecal incontinence. Most women included were of menopausal age. Three studies included sexually inactive women. Post-SNM follow-up varied from 3 to 36 months. Meta-analysis of efficacy results was not possible primarily due to the heterogeneity of the sexual and pelvic dysfunctions. The most specific questionnaire assessing FSF was the Female Sexual Function Index (FSFI) used in six studies. During follow-up all women showed statistically significant improvement (p < 0.05) in at least one FSFI domain compared to baseline. In one study statistically significant improvement (p < 0.05) in the FSFI pain domain was exclusively detected in women with neurological disease. Two studies, however, using the questionnaire to screen for sexual dysfunction did not find any statistically significant differences after SNM. The most severe problems associated with FSF concern loss of libido and reduction in vaginal lubrication which were resolved in one woman following removal of the SNM implant.

CONCLUSIONS

Actual data are still insufficient to definitely assert the positive effect of SNM on FSF.

Electrical Stimulation and Motor Recovery

In recent years, several investigators have successfully regenerated axons in animal spinal cords without locomotor recovery. One explanation is that the animals were not trained to use the regenerated connections. Intensive locomotor training improves walking recovery after spinal cord injury (SCI) in people, and >90% of people with incomplete SCI recover walking with training. Although the optimal timing, duration, intensity, and type of locomotor training are still controversial, many investigators have reported beneficial effects of training on locomotor function. The mechanisms by which training improves recovery are not clear, but an attractive theory is available. In 1949, Donald Hebb proposed a famous rule that has been paraphrased as “neurons that fire together, wire together.” This rule provided a theoretical basis for a widely accepted theory that homosynaptic and heterosynaptic activity facilitate synaptic formation and consolidation. In addition, the lumbar spinal cord has a locomotor center, called the central pattern generator (CPG), which can be activated nonspecifically with electrical stimulation or neurotransmitters to produce walking. The CPG is an obvious target to reconnect after SCI. Stimulating motor cortex, spinal cord, or peripheral nerves can modulate lumbar spinal cord excitability. Motor cortex stimulation causes long-term changes in spinal reflexes and synapses, increases sprouting of the corticospinal tract, and restores skilled forelimb function in rats. Long used to treat chronic pain, motor cortex stimuli modify lumbar spinal network excitability and improve lower extremity motor scores in humans. Similarly, epidural spinal cord stimulation has long been used to treat pain and spasticity. Subthreshold epidural stimulation reduces the threshold for locomotor activity. In 2011, Harkema et al. reported lumbosacral epidural stimulation restores motor control in chronic motor complete patients. Peripheral nerve or functional electrical stimulation (FES) has long been used to activate sacral nerves to treat bladder and pelvic dysfunction and to augment motor function. In theory, FES should facilitate synaptic formation and motor recovery after regenerative therapies. Upcoming clinical trials provide unique opportunities to test the theory.

Nerve stimulation for chronic pelvic pain and bladder pain syndrome: a systematic review

Chronic pelvic pain (CPP) and bladder pain syndrome (BPS) can have a negative impact on quality of life. Neuromodulation has been suggested as a possible treatment for refractory pain. To assess the effectiveness of tibial and sacral nerve stimulation in the treatment of BPS and CPP. We searched until July 2012: the Cochrane Library, EMBASE (1980-2012), Medline (1950-2012), Web of knowledge (1900-2012), LILACS (1982-2012) and SIGLE (1990-2012) with no language restrictions. We manually searched through bibliographies and conference proceedings of the International Continence Society. Randomized and prospective quasi-randomized controlled studies vs. sham nerve stimulation treatment or usual care of patients with CPP and BPS who underwent sacral or tibial nerve stimulation were included. Any studies involving transcutaneous stimulation were excluded. The outcome was a cure or improvement in symptoms. Three studies with 169 patients treated with tibial nerve stimulation were included; two for CPP and one for BPS. There were improvements in pain, urinary and quality of life scores. There were no reported data for sacral nerve stimulation. There is scanty literature reporting variable success of posterior tibial nerve stimulation in improving pain, urinary symptoms and quality of life in CPP and BPS. In view of the dearth of quality literature, a large multi-centered clinical trial investigating the effectiveness of electrical nerve stimulation to treat BPS and CPP along with the cost-analysis of this treatment is recommended.

Electrical stimulation of anal sphincter or pudendal nerve improves anal sphincter pressure

OBJECTIVE

Stimulation of the pudendal nerve or the anal sphincter could provide therapeutic options for fecal incontinence with little involvement of other organs. The goal of this project was to assess the effects of pudendal nerve and anal sphincter stimulation on bladder and anal pressures.

DESIGN

Ten virgin female Sprague Dawley rats were randomly allocated to control (n = 2), perianal stimulation (n = 4), and pudendal nerve stimulation (n = 4) groups. A monopolar electrode was hooked to the pudendal nerve or placed on the anal sphincter. Aballoon catheter was inserted into the anus to measure anal pressure, and a catheter was inserted into the bladder via the urethra to measure bladder pressure. Bladder and anal pressures were measured with different electrical stimulation parameters and different timing of electrical stimulation relative to spontaneous anal sphincter contractions.

RESULTS

Increasing stimulation current had the most dramatic effect on both anal and bladder pressures. An immediate increase in anal pressure was observed when stimulating either the anal sphincter or the pudendal nerve at stimulation values of 1 mA or 2 mA. No increase in anal pressure was observed for lower current values. Bladder pressure increased at high current during anal sphincter stimulation, but not as much as during pudendal nerve stimulation. Increased bladder pressure during anal sphincter stimulation was due to contraction of the abdominal muscles.

CONCLUSION

Electrical stimulation caused an increase in anal pressures with bladder involvement only at high current. These initial results suggest that electrical stimulation can increase anal sphincter pressure, enhancing continence control.

Pancolonic motor response to subsensory and suprasensory sacral nerve stimulation in patients with slow-transit constipation

BACKGROUND

Sacral nerve stimulation (SNS) is emerging as a potential treatment for patients with constipation. Although SNS can elicit an increase in colonic propagating sequences (PSs), the optimal stimulus parameters for this response remain unknown. This study evaluated the colonic motor response to subsensory and suprasensory SNS in patients with slow-transit constipation.

METHODS

Patients with confirmed slow-transit constipation were studied. Either a water-perfused manometry catheter or a high-resolution fibre-optic manometry catheter was positioned colonoscopically to the caecum. A temporary electrode was implanted transcutaneously in the S3 sacral nerve foramen. In the fasted state, three conditions were evaluated in a double-blind randomized fashion: sham, subsensory and suprasensory stimulation. Each 2-h treatment period was preceded by a 2-h basal period. The delta (Δ) value was calculated as the frequency of the event during stimulation minus that during the basal period.

RESULTS

Nine patients had readings taken with a water-perfused catheter and six with a fibre-optic catheter. Compared with sham stimulation, suprasensory stimulation caused a significant increase in the frequency of PSs (mean(s.d.) Δ value - 1·1(7·2) versus 6·1(4·0) PSs per 2 h; P = 0·004). No motor response was recorded in response to subsensory stimulation compared with sham stimulation. Compared with subsensory stimulation, stimulation at suprasensory levels caused a significant increase in the frequency of PSs (P = 0·006).

CONCLUSION

In patients with slow-transit constipation, suprasensory SNS increased the frequency of colonic PSs, whereas subsensory SNS stimulation did not. This has implications for the design of therapeutic trials and the clinical application of the device.

Pelvic floor therapies in chronic pelvic pain syndrome

Chronic pelvic pain syndrome is a poorly understood clinical entity associated with urinary symptoms, pelvic floor dysfunction, and multisystem disorders. Treatment of pelvic floor dysfunction is difficult and often frustrating for the patient as well as for the involved physician. The purpose of this review is to update clinicians on the latest research for the treatment of pelvic floor dysfunction in relation to chronic pelvic pain syndrome.