Bilateral transcutaneous tibial nerve stimulation for ...

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Received Date : 21-Apr-2015 Revised Date : 26-Jun-2015 Accepted Date : 03-Jul-2015 Article type

: Original Article

Bilateral transcutaneous tibial nerve stimulation for chronic constipation

F Iqbal, B Collins, GP Thomas, A. Askari, E Tan, RJ Nicholls, CJ Vaizey

Mr Fareed Iqbal, Clinical Research Fellow Department of Surgery, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom Miss Brigitte Collins, Biofeedback Nurse Specialist, Department of Physiology, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom Mr Gregory Thomas, Surgical Registrar, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom Mr Alan Askari, Clinical Research Fellow, Department of Surgery, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom Mr Emile Tan, Consultant Colorectal Surgeon, Department of Surgery and Cancer, Imperial College, London Prof R John Nicholls, Emeritus Professor of Surgery, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom Miss Carolynne J Vaizey, Consultant Colorectal Surgeon, St Mark’s Hospital and Academic Institute Watford Road, Harrow, HA1 3UJ, United Kingdom

Corresponding author: Miss CJ Vaizey, St Mark’s Hospital and Academic Institute, Northwick Park, Watford Road Middlesex HA1 3UJ. Tel: +44 2082354086 Email: [email protected]

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an 'Accepted Article', doi: 10.1111/codi.13105 This article is protected by copyright. All rights reserved.

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Conflicts of interest: None

Author contribution: FI-concept, design, data analysis, interpretation, drafting, BC-acquisition of data, concept. GT-concept, design, revision of the manuscript, AA-data analysis, statistical analysis, review of manuscript ET-study supervision, analysis, drafting of manuscript, RJN-study supervision, critical revision of the manuscript for important intellectual content, CJV-concept, study supervision, critical revision of the manuscript for important intellectual content

Abstract Aim: Chronic constipation is difficult to treat when symptoms are intractable. Colonic propulsion may be altered by distal neuromodulation but this is conventionally delivered percutaneously. Transcutaneous tibial nerve stimulation is non-invasive and cheap. The following study aimed to assess its efficacy in chronic constipation Method Eighteen patients (median age 46 years; 12 female,) with chronic constipation were recruited consecutively. Conservative and behavioural therapy had failed to improve symptoms in all. Thirty minutes of daily bilateral transcutaneous tibial nerve stimulation was administered by each patient at home for six weeks. The primary outcome measure was a change in Patient Assessment of Constipation Quality of Life (PAC-QOL) score. Change in Patient-Assessment of Constipation Symptoms (PAC-SYM), weekly bowel frequency and visual analogue scale (VAS) score were also measured. Results: Fifteen patients (12 Female) completed the trial. The PAC-QOL score improved significantly with treatment (median 2.95 pre-treatment, interquartile range (IQR) 1.18, to median 2.50 IQR 0.70 post-treatment; p = 0.047). There was no change in PAC-SYM score (median 2.36 IQR 1.59, to median 2.08 IQR 0.92; p = 0.53). Weekly stool frequency

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improved as did VAS score but these did not reach statistical significance (p= 0.229 and 0.161). The PACQOL and PACSYM score both improved in four (26%) patients. Two patients reported complete cure. There were no adverse events reported. Conclusion: Bilateral transcutaneous tibial nerve stimulation appears to be effective in a quarter of patients with chronic constipation. Carefully selected patients with less severe disease may benefit more. This requires further study.

What does this paper add to the literature? The paper demonstrates the efficacy of a previously untested therapy for patients with chronic functional constipation. Bilateral transcutaneous tibial nerve stimulation seems to be effective in about a quarter of patients.

Introduction Chronic constipation is common, highly disabling and difficult to treat when

symptoms

are

intractable.

population are affected

(1,

2)

Between

2-28%

of

the

general

with approximately 2% presenting to

secondary and tertiary care.(3) Chronic functional constipation refers to symptoms that are present for more than six months(4) and not This article is protected by copyright. All rights reserved.

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attributable to medication, underlying medical conditions or obstructing luminal lesions. Almost three quarters will have constipation that is functional in nature.(5) Despite specialist behavioural therapies, up to a third will remain symptomatic.(6, 7) When behavioural and medical treatment fails, colectomy or intestinal stoma are considered.(8) These procedures do not resolve constipation in most patients.(9) A stoma can also introduce further psychological and physical morbidity.(9-12) Re-establishing normal colonic motor function may be possible with neuromodulation by sacral nerve stimulation (SNS).(13,

14)

The short to medium-term outcomes are reasonable,

although much of this data is derived from small open-labelled caseseries.(15-18) The long-term efficacy of SNS appears favourable particularly in patients with obstructive defecation,(19) but some authors have reported poor results in unselected patients(20) The recent publication of consensus guidelines on the selection of patients for SNS may improve the outcome,

(21)

but SNS is expensive,

(22)

moderately invasive and can

be associated with postoperative complications.(23) An alternative method of neuromodulation is percutaneous tibial nerve stimulation (PTNS). The tibial nerve arises from nerve roots L4-S3, the same nerve roots that supply the pelvic floor and hindgut. PTNS has been used to treat faecal incontinence,(24) overactive bladder syndrome(25,

26)

and chronic pelvic pain.(27) It has also shown efficacy in constipation.(28) The precise mechanism of PTNS is unknown. Transcutaneous tibial nerve


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Table 5. Visual analogue scale (0-100) and weekly bowel frequency in 15 patients undergoing transcutaneous tibial nerve stimulation (TTNS). Data are expressed as median (interquartile range).

Domain Visual analogue

Baseline

Six weeks

P value

0 (11)

20 (100)

0.229

1.5 (5)

2.5 (6)

0.161

scale Weekly bowel frequency

Figure 1: Placement of the live pad immediately posterior to the medial malleolus


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months.(4) Colonic work-up was undertaken before biofeedback and included anorectal physiology, colonic transit and defecating proctography in patients with evacuation difficulty. All radiographic investigations were assessed by a consultant radiologist. Anorectal manometry was carried out by a senior gastrointestinal physiologist. Patients were categorised into slow transit, pelvic floor dysfunction, combined pathologies or normal transit according to the results of the tests. All the patients provided written informed consent in accordance with the ethical principles laid out by the Declaration of Helsinki.

Endpoints A bowel and laxative diary was kept a week before and during the final week of stimulation which recorded defecation frequency, number of unsuccessful attempts at defaecation, straining, digitation and need for rescue laxatives. Questionnaires were completed on Patient-Assessment of

Constipation

Symptoms

(PAC-SYM)(31),

Patient

Assessment

of

Constipation Quality of Life (PAC-QoL),(32) and a 0-100 visual analogue scale (0 ‘very unhappy’ 100 ‘very happy’) based on patients’ response to ‘how happy are you with the way your bowel has been functioning’. All measures were repeated immediately after six weeks of stimulation.


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Patients were taught how to perform transcutaneous tibial nerve stimulation during recruitment. This was self-performed at home over six consecutive weeks,using the NeuroTrac™ Continence device (Verity Medical Ltd, Hampshire UK) via two 50mm x 50mm pads. The live pad was placed immediately behind the medial malleolus where the tibial nerve is most superficial (Figure 1). Patients were shown how to ensure accurate pad placement eg greater toe flexion when the amplitude was increased. Further instructions were given on a patient information sheet which included a photograph demonstrating correct pad and lead placement. Continuous stimulation was provided for thirty minutes daily for six weeks at a frequency of 14Hz, pulse width of 220µs, with a rest time of 99 seconds and two seconds at an amplitude of tolerable sensory threshold (maximum 33mA) but below motor threshold. Patients were instructed to perform stimulation in the morning after waking or immediately after breakfast. The device was locked so the parameters could not be altered. They were

asked to refrain from taking

their

usual constipation

medication unless symptoms became too severe. This was recorded separately on a laxative sheet. Those on rectal irrigation were asked to stop during the trial. Those who underwent stimulation for less than four weeks, or had three or more consecutive missed days over three consecutive weeks were excluded from the final analysis. The primary


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outcome measure was the median change in PAC-QOL score. Secondary end points are described above. Statistical analysis The distribution of the data was non-parametric. Statistical analysis was carried out using the Wilcoxon rank sum test which expressed data as median and interquartile range. A p value of 0.05 or less was considered statistically significant. Statistical analysis was carried out using SPSS (IBM® Version 22.0). As this was a pilot study, a power calculation was not performed.

Results Eighteen patients (12 (67%) female) of median age 47 (interquartile range: 27-74) years started the trial which fifteen (12 (83%) female) completed. Three (17%) patients did not wish to continue the trial as one had concurrent medical conditions and two could not commit to daily stimulation. Demographics of the participants are summarised in Table 2. The PAC-QoL score improved in most patients (60%, 9/15), but when a PAC-QoL score difference of at least one point was made a criterion for clinical improvement, just over a quarter (26%, 4/15) improved (Table 3). Similarly, just over half the patients improved on the PAC-SyM score (Table 4), but when the same criteria were applied, only two (13%) improved with improvement of both the PAC-QoL and PAC-SyM scores in This article is protected by copyright. All rights reserved.

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each case. Overall four (26%) patients improved as judged by both PACQoL and PAC-SyM domains and were classified as ‘true responders’. Two patients reported complete cure. There was no difference in the demographic or clinical indices between responders and non-responders. On pooled analysis there was a statistically significant improvement in PAC-QoL before and after TTNS (p=0.047). Psychosocial well-being and anxiety and concern sub-domains improved in particular with no changes to the physical discomfort (0.071) or satisfaction sub-domains (p=0.283) Rescue laxative treatment was required by ten (66%) patients during the trial. This was not linked to reported outcome as the group included three of the four ‘true responders’. Satisfaction of bowel movement, as judged by the VAS was seen in 40% of patients when a threshold of at least 50% improvement from baseline was set. Weekly bowel frequency did not change (Table 5). There were no adverse events reported. All patients managed to complete at least half of the stimulation during the morning hours.

Discussion To the best of our knowledge the present study is the first to demonstrate efficacy,

albeit

partial,

from

bilateral

transcutaneous

tibial

nerve

stimulation in chronic functional constipation. The treatment was welltolerated, easy to administer and safe. The most rigorously validated constipation-specific quality of life tool (PAC-QoL) was selected as the


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primary outcome measure, with the most robust effect size (one point difference) being applied to the analysis.(32) The immediate outcome based on this analysis demonstrates the effectiveness of TTNS for chronic constipation in at least of quarter of patients. There appeared to be a discrepancy between reported improvement in PAC-QoL score (26%) and PAC-SyM

(13%).

Similarly,

on

pooled

analysis

PAC-QoL

score

improvement was statistically significant whilst PAC-SyM score was not. This may be explained on the basis that TTNS specifically improved psychosocial well-being and anxiety and concern regarding constipationassociated symptoms. These subdomains are not evaluated in the PACSyM tool. It is perhaps more appropriate to concentrate on the outcome of PAC-QoL as holistic symptoms should be given careful consideration in functional bowel disease. Moreover, the PAC-QoL is the gold standard in constipation trial reporting. Stimulation parameters in the present study were kept the same as those of conventional implantable SNS.(15) In a double-blind randomised controlled trial investigating the optimal implantable SNS parameters for constipation, continuous stimulation at a frequency of 14Hz and pulse width of 210µs was found to be most effective.(33) The present study used the same settings but a higher pulse width of 220µs was only available with the device used; the effect of this difference is likely to be negligible. An hour of daily stimulation for six weeks was based on previous transcutaneous tibial nerve stimulation studies.(34,

35)

Neuromodulation

was delivered during the morning after waking or immediately after This article is protected by copyright. All rights reserved.

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breakfast. Colonic activity is at its greatest during these times(36) and the present study aimed to improve colonic propulsion whilst the activity was most frequent. Aberrant colonic motor function has been considered to be a possible cause of constipation. This can be from intrinsic or extrinsic neuronal dysfunction.(37) The depletion of colonic propulsion mediating cells like interstitial cells of Cajal, enteric glial cells and enteric interneurones have been demonstrated in slow transit constipation.(38,

39)

Generalised or autonomic specific neuropathies affecting parasympathetic innervation to the sigmoid and rectum has been shown in the absence of intrinsic neuropathies suggesting an alternative aetiology.(37) The precise pathology may be multi-factorial. The effects of distal neuromodulation on colonic activity have been evaluated in animal studies.(40) It appears to increase distal colonic transit and motility in conscious rats.(41) Gastro-colic reflexes may also be modulated after distal neuromodulation via the vagus nerve.(42) These effects may be additive as both have been recorded simultaneously in test subjects(43), but the mechanism of distal neuromodulation in the context of aberrant colonic function is untested. There have been two reports demonstrating the efficacy of distal neuromodulation in constipation. A pilot study(28) of eighteen

patients

undergoing

PTNS

for

12

weeks

demonstrated

statistically significant improvements in PAC-QoL and Wexner score with no change of colonic transit whilst a study from China demonstrated improvement in the severity of constipation as a result of improved parasympathetic

drive.(44)

These

mechanisms


appear

contradictory

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although it may be possible that certain patients with lesser degrees of colonic dysfunction may respond to distal neuromodulation better than those with more severe disease. The efficacy of distal neuromodulation transcutaneously or percutaneously may be improved with careful patient selection. The sacral plexus may have asymmetrical dominance with one side having

greater

influence

over

its

targets

than

the

contralateral

counterpart.(45) Cortical processing of anal sensation has shown similar asymmetry

with

the

right

primary

somatosensory

cortex

holding

dominance over the left; this may hold true for rectal sensation in some individuals.(46) Bilateral nerve stimulation may overcome an underlying asymmetry and

activate a greater number

of ascending

afferent

pathways. This has been demonstrated in faecal incontinence.(35) Future studies should use bilateral as opposed to unilateral stimulation. The present study is limited in a number of ways. It is small, uncontrolled and under-powered. Furthermore, changes of the colonic indices were not measured after stimulation. This casts uncertainty on the underlying mechanism. Without this analysis, improvements seen in a quarter of patients may have been due to a placebo effect. A further limitation is that follow up was short and judgements over efficacy can only be discerned immediately at the end of treatment. Despite these limitations, statistically significant improvements in PAC-QoL were apparent which warrants further research.


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Daily self-administered bilateral transcutaneous tibial nerve stimulation is safe and accepted by patients with chronic constipation. It appears affective in the short-term in a quarter of patients.

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Table 1. Inclusion and exclusion criteria Inclusion Criteria

Exclusion criteria

Signed consent form

Poor dexterity/mobility or vision

Age 18-90 years of age

Peripheral neuropathy

Failed Biofeedback (minimum of Skin eruption two sessions) stimulation

at

the

site

No concurrent neuromodulation

Recent surgery to the lower limb

Rome III defined constipation

Metallic implant in the lower limb

of

Willingness to stop laxatives and Full thickness rectal prolapse irrigation during trial in the absence of severe symptoms Inflammatory bowel disease Neurological disorders Psychological distress Pregnancy or wishing to become pregnant

Table 2. Baseline characteristics of patients who completed the trial. Data are given as median with interquatile range in brackets.

Number Gender Age Ethnic origin

Number of years with constipaiton Type of constipation

15 12 female 47 years (27-74) 13 White-British/White other 1 South-Asian 1 Afro-caribean 8 (2-30) Slow transit 7 Pelvic floor dysfunction 4 Combined pathology 2 Normal transit 2


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Table 3. Patient Assessment of Constipation Quality of Life (PAC-QoL) score in 15 patients undergoing transcutaneous tibial nerve stimulation (TTNS). Data are expressed as median (interquartile range).

PACQOL domain Physical

Baseline

Six weeks

P value

3.50 (1.25)

2.75 (1.50)

0.07

Psychosocial

2.75 (1.88)

1.75 (1.38)

0.05

Worries and

3.09 (1.00)

2.54 (0.91)

0.04

Satisfaction

3.80 (1.00)

3.00 (1.60)

0.283

Total score

2.95 (1.18)

2.50 (0.70)

0.04

discomfort

concerns

Table 4. Patient-Assessment of Constipation Symptoms (PAC-SyM) score in 15 patients undergoing transcutaneous tibial nerve stimulation (TTNS). Data are expressed as median (interquartile range).

PAC-SyM

Baseline

Six weeks

P value

domain Abdominal

2.75 (0.75)

2.50 (1.75)

0.207

Rectal Symptoms

0.66 (1.67)

1.00 (1.34)

0.692

Stool Symptoms

2.80 (1.60)

2.40 (0.80)

0.624

Total score

2.36 (1.59)

2.08 (0.92)

0.53

Symptoms


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Table 5. Visual analogue scale (0-100) and weekly bowel frequency in 15 patients undergoing transcutaneous tibial nerve stimulation (TTNS). Data are expressed as median (interquartile range).

Domain Visual analogue

Baseline

Six weeks

P value

0 (11)

20 (100)

0.229

1.5 (5)

2.5 (6)

0.161

scale Weekly bowel frequency

Figure 1: Placement of the live pad immediately posterior to the medial malleolus
