Pre, before stimulation; PNE, percutaneous nerve evaluation. All temporary percutaneous electrodes were placed as a day-case and screening was performed for a median of 21 days range, 21—29 days. Permanent implantation was performed at a median of 1 month range, 0—5 months after removal of the temporary electrode; in-patient time was 3 days range, 1—6 days. There were no major complications, no infections of permanent implants and no implants have had to be removed. One superficial skin infection during percutaneous screening resolved after removal of the temporary electrode and delayed permanent implantation proceeded successfully.
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There were two lead dislodgements early in the series replaced surgically with good result. Further implants were fixed securely to the periosteum. Patients occasionally experienced minor localised electric shocks when passing through ambient electrical or magnetic fields. Deactivation of the pulse generator magnet renders the implant less sensitive and eliminated this problem. All were considering the formation of a colostomy.
Exclusion criteria included previous abdominal surgery, hysterectomy, current or planned pregnancy, anatomical abnormality on proctography and any significant psychological disturbance or contribution to symptoms as judged clinically by the investigators. Correctable causes were excluded via clinical investigation, including colonoscopy and proctography. Whole gut transit time was prolonged in two patients patients 1 and 2.
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A 3-week bowel diary, the Wexner constipation score, a symptom analogue score, the SF assessment and anorectal physiological testing were performed at baseline, at the end of 3-weeks of temporary stimulation, 1 month after temporary stimulation before permanent implantation, and at 1, 3 and 6 months after permanent implantation. The transit study was repeated at 6 months. During all assessment periods, patients were asked not to take laxatives. The technique for SNS was identical to that previously described with all stimulation parameters set to the same levels.
Due to the small number of patients, the results are presented in full, and not statistically analysed.
Percutaneous temporary screening was performed for 21—22 days without complication. Permanent implantation was performed 9 months range, 1—16 months after screening as a one-stage procedure, median operative time of 70 min range, 60— min , discharge day 3 range, days 2—4 without complication. There was an associated improvement in the evacuation score 4 versus 1 , the percentage time with pain and bloating, the Wexner score 22 versus 10 and the patient symptom analogue score 25 versus Quality of life improved in all subscales, except health-transition, with both temporary and permanent stimulation.
Figure 1 The effect of sacral nerve stimulation on bowel frequency in constipation. Pre refers to baseline levels before stimulation, PNE percutaneous nerve evaluation. Post is after temporary screening, without stimulation, prior to implantation. One, three and six months refer to time after permanent implantation. Evaluation was continued for the 3-week period after screening following removal of the temporary stimulation wire, prior to permanent implantation. All symptoms, bowel frequency and laxative use returned to baseline levels in this period. Patient 4 underwent permanent implantation without complication with initial benefit, but was involved in a major road traffic accident one week after surgery.
This caused movement of the implanted electrode and a return to baseline levels. This is currently being treated with adjustment of the electrode settings. All patients used regular laxatives prior to stimulation. During screening, no patient required laxatives and none of the three patients with symptomatic improvement from permanent stimulation required laxatives. Two female patients aged 36 years with severe, resistant idiopathic constipation who had been implanted with a permanent stimulator 12 months previously were studied patients 1 and 2 in constipation study.
One year was chosen to ensure that the clinical benefit was maintained in the medium-term, and so that the optimal stimulation parameters had been determined. Three 2-week periods were assessed using bowel diaries, scores, quality of life and anorectal physiology as previously described.
The first period was after 1 year of permanent stimulation with the stimulation on. The second and third periods were with the stimulation either on or off, the primary investigator and patient blinded. Both patients used sub-sensory stimulation; thus, neither was aware whether the stimulation was on or off.
A clinical scientist controlled the stimulation at each visit using external telemetry.
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The electrodes were, therefore, undisturbed and the primary investigator blinded. Clinical benefit appeared to be maintained at 1 year of chronic stimulation compared to baseline results. Once stimulation was removed, in a blinded manner, benefit was rapidly lost with bowel frequency and symptoms returning to baseline levels Table 2.
Quality of life improved with a year of chronic stimulation. There were no complications and both patients rapidly regained their original benefit once stimulation was re-instated. Table 2 Clinical and physiological results for placebo-controlled cross-over study. Sixteen patients, 15 women, aged 59 years range, 38—71 years who had been successfully treated with permanent SNS for resistant faecal incontinence were studied at 27 months range, 2—62 months after implantation.
Patients who had undergone a previous bowel resection or who had any evidence of spinal cord injury were excluded as this may potentially disrupt the autonomic innervation. Stimulation was then turned off and the change in flux recorded. Measurements were then repeated with step-wise 0. Stimulation was ceased if painful as this may cause autonomic arousal. Statistical analyses were performed for the grouped blood flux data using the Wilcoxon paired ranks test comparing no stimulation with baseline chronic stimulation, and at each separate level of acute stimulation.
An analysis of variance model and regression analysis was also performed. There were no complications, and no patient experienced a decrease in symptomatic benefit due to the Doppler recording and temporary alteration of stimulation levels. The rate of change of blood flux in response to changes in stimulation amplitude occurred within seconds and steady state readings were always reached within 1 min. The median level for chronic stimulation was 2. The median flux with chronic stimulation was flux units range, — flux units. Step-wise 0. Figure 2 Change in grouped laser Doppler flux in response to amplitude of stimulation.
This research has demonstrated unequivocally that sacral nerve stimulation can improve patients with disorders of lower bowel motility when conventional treatment has failed. At time of submission, this was the largest reported series for patients with faecal incontinence treated with SNS. All patients had symptoms severe enough to consider a colostomy and had failed all other conventional treatment.
Dramatic clinical benefit appears to be maintained, without deterioration, in the medium-term with an associated improvement in quality of life. Subsequent reports have confirmed this clinical benefit and have emphasised the safety of this procedure. The surgical technique has evolved during this research to avoid temporary screening lead dislodgements and pain with permanent implants.
Temporary screening offers a minimal morbidity, pain-free, day-case technique for predicting success prior to any invasive surgery. This is extremely rare in any surgical technique and is a major advantage of SNS. The definitive implant is a relatively minor procedure with low morbidity, especially compared to alternative surgical options. The operative site is distant from the bowel so previous procedures do not complicate surgery. With a one-stage implant, 1 month after temporary stimulation, the infection risk appears to be low and this is the author's current technique.
Variations have been employed, particularly the use of a percutaneously tunnelled screening electrode that is later permanently implanted, which may lead to a higher infection rate. The physiological mechanism of action is currently unclear but SNS has the potential to affect all of the structures involved in continence and defecation.
This may be the reason that it appears to have clinical superiority over other techniques that address one aspect only, normally the anal sphincter. The study on constipated patients showed a marked improvement in three of four patients in the short term. While this is pilot data only, it has shown proof-of-concept that SNS can produce clinical benefit when other treatments have failed in this multifactorial condition. This work has lead to the design and development of a currently running international multicentre trial for SNS in constipation in eight European centres.
The cross-over trial indicated that this previously unreported beneficial clinical effect is unlikely to be due to placebo. The rapid loss of benefit once stimulation was removed, after a year of successful treatment, suggests that constant stimulation is required and that the underlying mechanism is a rapidly reversible neurological mechanism. This finding agrees with a previous similar study in patients treated with SNS for incontinence.
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Further larger studies would be indicated. While the precise physiological mechanism is unclear, there is evidence that all aspects of the sacral nerve plexus are affected: The most consistent finding is a modest increase in external anal sphincter function, modulated through the efferent somatic nerve fibres. This finding may have implications for the level of future therapeutic stimulation.
It is likely that chronic SNS produces the observed beneficial clinical effect through modulation of all of these nerve fibres. The relative contribution of each and the central effects on higher centres remain unknown and an area for future research. This is not inexpensive; however, it is comparable to other surgical procedures, and has a far higher success rate and lower morbidity. Compared to conservative long-term bowel care, SNS reaches financial advantage after 5 years. Overall, there is little doubt that sacral nerve stimulation can dramatically improve patients with faecal incontinence when other treatments have failed.
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There is a possibility the same may be true for resistant idiopathic constipation but the current data are too sparse to support this fully. The mechanism of action is neurological in basis but the precise nature remains to be elucidated. However, it has been a personal privilege to be in the right place at the right time in order to be allowed to take this treatment from research into current specialised colorectal clinical practice. I would like principally to thank Prof.