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Patkawat Ramart, M.D., Phadungsak Sangsoad, M.D.
Division of Urology, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700,ailand.
Sacral Neuromodulation in the Treatment of
Non-Neurogenic Female Lower Urinary Tract
Dysfunction; First Case-series and Systematic
Review of Literature
ABSTRACT
Objective: To demonstrate which types of non-neurogenic female lower urinary tract dysfunction (LUTD) respond
to sacral neuromodulation (SNM) aer the failure of all non-invasive treatments.
Materials and Methods: Female LUTD performed SNM between 2017 and 2019 were retrospectively reviewed. A case
with anatomical or neurological abnormalities were excluded by thorough physical examination and investigations.
e specic type of LUTD, including midurethral obstruction (MUO), was diagnosed by videourodynamics
(VUDS). Clinical diagnoses, including idiopathic urinary retention (IUR), voiding dysfunction (VD) and refractory
overactive bladder (OAB), were used instead of VUDS diagnosis when the result was normal or inconclusive. e
International Prostate Symptom Score (IPSS) and Overactive Bladder Symptom Score (OABSS) in ai version
were used to compare between pre and post-treatment. Responder was dened as an IPSS and/or OABSS decreased
more than 50% from baseline.
Results: Total 21 cases were performed SNM. e average age was 49.6 (24–80) years. e average pre-treatment
IPSS and OABSS were 23.4 and 6.4 as well as average post-treatment IPSS and OABSS were 13.7 and 3.8. Only 9
out of 21 cases (42.9%) showed improvement aer SNM. e responders included 7 out of 11 MUO (63.6%), 1 out
of 4 IUR (25.0%), and 1 out of 3 OAB (33.3%). None of the VD cases responded to SNM.
Conclusions: SNM is another option for female patients with LUTD who have failed to respond to conservative
treatments. Aer completely excluding anatomical and neurological abnormalities, the types of LUTD having a
chance to respond to SNM are MUO, IUR, and OAB.
Keywords: Lower urinary tract dysfunction, Female, Sacral neuromodulation (Siriraj Med J 2021; 73: 732-737)
Corresponding author: Patkawat Ramart
E-mail: patkawat.ram@mahidol.ac.th
Received 6 September 2021 Revised 14 October 2021 Accepted 14 October 2021
ORCID ID: https://orcid.org/0000-0003-0452-367x
http://dx.doi.org/10.33192/Smj.2021.94
Abbreviation
LUTD : Lower urinary tract dysfunction
SNM : Sacral neuromodulation
VUDS : Videourodynamics
BOO : Bladder outlet obstruction
MUO : Midurethral obstruction
DU : Detrusor underactivity
IUR : Idiopathic urinary retention
VD : Voiding dysfunction
OAB : Overactive bladder
Ramart et al.
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INTRODUCTION
Lower urinary dysfunction (LUTD) is a functional
problem that mainly causes lower urinary symptoms in
women and usually aects their quality of life. Functional
abnormalities in each patient may consist of bladder and/or
outlet dysfunction. Because LUTD is a dynamic abnormality
and changes over time, the appropriate management
for LUTD should be conservative treatment and/or
medication. However, lower urinary tract symptoms may
not properly be alleviated by non-invasive treatment; while
invasive surgery will rarely be considered due to the risk
of a permanent change of function. Neuromodulation, a
treatment using electrical stimulation directly to the nerve
in order to modulate the reexes that inuence the bladder,
sphincters, bowel, and pelvic oor
1
to restore normal
lower urinary tract function, has been widely accepted
for treating LUTD and is considered as a non-invasive
procedure. Nowadays, there are many neuromodulation
procedures that have been used for treating LUTD, but
the most popular one is sacral neuromodulation (SNM),
which has supported from many scientic studies. e US
FDA has approved the use of InterStim™ or SNM for the
treatment of urgency-frequency syndrome, urinary urge
incontinence, and non-obstructive urinary retention.
2
In ailand, neuromodulation has been used in many
neurological conditions but there has never had a study
of neuromodulation for treating LUTD. Consequently,
this study aims to demonstrate our experience and to
provide the LUTD characteristics of patients who have
a chance to obtain a benet from SNM.
MATERIALS AND METHODS
We retrospectively reviewed the medical records
of 21 female patients with non-neurogenic LUTD who
were performed SNM between 2017 and 2019 in our
hospital. is study was approved by our institute IRB,
number 714/2562(IRB2)
Patient selection
e inclusion criteria were female patients with
LUTD who had not responded or had an unsatisfactory
response to all conservative treatments for more than 6
months. All cases would like to try SNM aer counselling
and understanding the risks and benets of procedure.
Further, physical and neurological examination must reveal
no signicant anatomical or neurological abnormality that
could probably be a cause of the LUTD. All the cases had
videourodynamics (VUDS) performed followed by the
International Continence Society (ICS) recommendation
3
in order to diagnose a type of functional abnormality
and to get a clear urodynamic diagnosis before SNM was
performed. Because surface electromyography during
VUDS was unreliable, the result was not considered as
a part of diagnosis and uoroscopic imaging was used
instead of it. In cases of normal or inconclusive result
due to situational inability to void, clinical diagnosis was
used for the grouping instead of urodynamic diagnosis.
Denitions
According to ICS terminology 2010, the denition of
characteristics of LUTD consist of an overactive bladder
(OAB), dened as urinary urgency, usually accompanied
by frequency and nocturia, with or without urgency
urinary incontinence, in the absence of urinary tract
infection or other obvious pathology; voiding dysfunction
(VD), dened as an abnormally slow and/or incomplete
micturition; detrusor underactivity (DU), dened as a
detrusor contraction of reduced strength and/or duration,
resulting in prolonged bladder emptying and/or a failure
to achieve complete bladder emptying within a normal
time span; and bladder outlet obstruction (BOO), dened
as a reduced urine ow rate and/or presence of a raised
post-void residual urine and an increased detrusor
pressure.
4
e urodynamic criteria for the diagnosis of
female BOO were described in Blaivas’s study.
5
In this
group, the point of obstruction could be demonstrated
by uoroscopic examination on VUDS so that specic
term, including midurethral obstruction (MUO), was used
instead of BOO. Urethral stricture must be excluded by
cystourethroscopy in all BOO cases. In cases of normal
or inconclusive VUDS, the clinical diagnosis consisted
of voiding dysfunction (VD), dened as a maximal urine
ow rate equal to or less than 12 ml/sec with or without
post-void residual urine; idiopathic urinary retention
(IUR), dened as a past or current inability to void; and
refractory overactive bladder (OAB), dened as OAB
which had failed to respond to conservative treatment
and medications or led to intolerable adverse events.
Responders were dened as being cured or showed an
improvement aer SNM.
Measurement
e validated questionnaires in the ai language,
including the International Prostate Symptom Score (IPSS)
6
and Overactive Bladder Symptom Score (OABSS)
7
, were
used as a symptom measurement tool. Cure was dened
as an IPSS and/or OABSS improvement of more than
80% from baseline, while improvement was dened as an
IPSS and/or OABSS improvement of between 50% and
80% from baseline within 7-30 days aer implantation
and the last follow-up for the response cases. Responder
was dened as a case who was cure or improvement aer
SNM.
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Procedure
Sacral neuromodulation (SNM) is usually performed
in two stages: a test phase and a phase with implantation
of an implantable pulse generator (IPG) by using the
InterStim II® system (Medtronic). e test phase utilized
two techniques: temporary lead implantation, called
percutaneous nerve evaluation (PNE), and permanent
tined lead implantation, composed of four leads and a
hook. e full SNM system consisted of a permanent
tined lead and IPG. Lead implantation was performed
in the prone position, in a well-prepared sterile eld and
under local anesthesia with light sedation. Fluoroscopic
guidance was used to identify the 3
rd
sacral foramen in
two-dimensions, in the anteroposterior and lateral views.
A 20-gauge needle in the set of SNM was used to make a
puncture at 2 cm cephalad to the 3rd sacral foramen in
the anteroposterior view and at the 45°–60° axis in the
lateral view. e needle was passed through the foramen
and stopped at the anterior surface. e proximal end of
the needle was connected to an external pacemaker and
then electrical stimulation was given. e proper position
of the needle was dened by the patient reporting feeling
a tickling sensation at the perianal area, anus, and/or
vagina, called a sensory response and demonstrating anal
contraction, called a motor response. If the selected site
did not demonstrate any response, the procedure would
be repeated at the contralateral site in the same step. e
needle stylet was then removed. Either a temporary lead
or permanent lead was inserted via the needle and placed
in a proper position by checking the sensory and motor
responses. For PNE, the lead was xed directly at the
puncture site using a transparent medical dressing. For
the permanent lead, a subcutaneous tunnel was created by
a trocar with a plastic tube from the puncture site to the
subcutaneous pocket at the right buttock and the lead was
connected to an extended wire to directly connect to an
external pacemaker in order to prevent contamination.
Due to the easy displacement of the PNE lead, some
cases reporting no response might repeat either PNE or
permanent tined lead implantation if the patient agrees.
During the test phase, the external pacemaker was used
as an electrical generator and the implanted patient
could adjust the intensity of the electrical stimulation by
monitoring their feeling in the perianal area, anus, and
vagina. If the feeling was too much, electrical stimulation
could be reduced by remote control. For evaluation, if
a patient reported symptoms improvement of more
than 50% from baseline by IPSS and OABSS, full SNM
system implantation would be performed within 1-4
weeks. Because of the high cost of full SNM system
implantation, PNE was considered as a rst step in all
cases who had unsuccessful VUDS or where there were
doubts about the benet of SNM. All cases of full SNM
system implantation were supported by the high cost
treatment project of our hospital foundation.
Statistics
e results were presented using descriptive statistics
as a frequency and percentage for categorical data, as
well as average for continuous data.
RESULTS
In total, 21 cases of female LUTD who had SNM
performed. e average age was 49.6 (24 – 80) years.
e types of LUTD consisted of MUO 11 cases, IUR 4
cases, VD 3 cases, and OAB 3 cases. MUO and VD cases
were treated by non-invasive management including
behavioral therapy, pelvic oor muscle rehabilitation
and oral medications. IUR cases were initially treated by
indwelling catheter and then performed clean intermittent
catheterization. OAB cases were treated step by step
including rst - single oral bladder relaxant, second -
combination of oral high dose bladder relaxant and last
- 100 unit of intradetrusor botulinum toxin A injection.
e average pre-treatment IPSS and OABSS were 23.4
and 6.4 as well as the average post-treatment IPSS and
OABSS were 13.7 and 3.8. (Table 1) Only 9 out of 21
cases (42.9%) were cured or improved aer SNM. e
responders included 7 out of 11 MUO (63.6%), 1 out
of 4 IUR (25.0%), and 1 out of 3 OAB (33.3%). None of
the VD cases responded to SNM. Twelve of 21 cases had
complete VUDS successfully performed. (Table 2) Only
8 out of 9 responders had fully implanted SNM and the
average follow-up was 15.4 (4.4 – 32.4) months, while the
average IPSS and OABSS were 8.4 and 2.7, respectively.
One case decided not to continue with SNM because of
an awareness of the foreign body and fear of the long-
term consequences (Table 3). In total, 6 out of 8 cases
reported and considered themselves cured. No adverse
events were reported in all cases.
DISCUSSION
Female LUTD without anatomical and neurologic
abnormality is a challenging condition. Importantly, it
is not a life-threatening condition but always aects the
patient’s quality of life. Because of the dynamic changes
that can occur, the most appropriate treatment, including
conservative and medical treatment, should be reversible
over time, meaning that invasive surgery is not an ideal
option. However, while most patients are properly treated
by conservative and medical treatment, some patients
may not achieve their goal. SNM is another treatment
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TABLE 1. Comparison between average pre- and post-treatment IPSS and OABSS in each type of LUTD.
TABLE 2. Case number, diagnosis and videourodynamics parameters in each case.
Type of LUTD No.
IPSS OABSS
Pre-treatment Post-treatment Pre-treatment Post-treatment
MUO
Responder 7 23.7 5.4 6.0 1.9
Non-responder 4 18.3 15.0 3.5 2.6
IUR
Responder 1 34.0 6.0 6.0 3.0
Non-responder 3 27.3 22.7 4.0 2.7
DV
Responder 0 - - - -
Non-responder 3 25.3 23.3 8.3 8.3
OAB
Responder 1 15.0 0 9.0 0
Non-responder 2 15.5 15.5 11.0 11.0
Free
Urodynamic parameters
Case
Age Dx Group VV PVR uroow
no.
Qmax
Catheter Pdet at Fluoroscopic
Qmax Qmax ndings
1 35 MUO Responder 178 0 12.9 - - Mid
2 54 MUO Responder 115 155 - 4.2 80 Mid
3 41 MUO Non-responder 67 0 13.8 4.8 51.5 Mid
4 54 MUO Responder 40 205 - 2.1 57.5 Mid
5 68 MUO Responder 81 154 25 4.3 23 Mid
6 53 MUO Responder 376 0 16 16.4 26.5 Mid
7 53 MUO Non-responder 144 0 - 10.3 61.2 Mid
8 38 MUO Non-responder 210 0 18.8 - - Mid
9 24 MUO Responder 65 0 - 8.8 24 Mid
10 76 MUO Responder 80 96 - 5 25 Mid
11 80 MUO Non-responder 274 63 11 8.8 37.2 Mid
12 42 IUR Non-responder 199 202 11.6 - - -
13 45 IUR Non-responder 161 80 6.9 - - -
14 31 IUR Non-responder 126 150 10.2 - - -
15 36 IUR Responder 70 600 4 - - -
16 38 VD Non-responder 592 0 12 - - -
17 34 VD Non-responder 233 200 10 - - -
18 65 VD Non-responder 256 0 11.5 - - -
19 76 OAB Responder 491 0 - 21.9 17.1 No BOO
20 41 OAB Non-responder 420 0 - 25.5 30 No BOO
21 59 OAB Non-responder 180 0 - 24.2 28.2 No BOO
Abbreviations: Dx : diagnosis, VV : voided volume (ml), PVR : post-void residual urine (ml), Qmax : maximal urine ow rate (ml/sec),
Pdet@Qmax : detrusor pressure at maximal urine ow rate (cmH2O), Mid : midurethral obstruction, BOO : bladder outlet obstruction
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TABLE 3. Comparison between pre- and post-treatment IPSS and OABSS in responder group at the last follow up.
Case Age Followtime
IPSS OABSS
no. (year)
Diagnosis
(month)
Pre- Post- Pre- Post- Status
treatment treatment treatment treatment
1 35 MUO 32.4 31 0 3 0 Cure
2 54 MUO 21.2 40 1 15 1 Cure
4 54 MUO 7.1 22 11 6 2 Improvement
5 68 MUO 13.0 20 8 4 3 Improvement
6 53 MUO 12.7 15 0 2 2 Cure
9 24 MUO - 19 - 11 - Not perform
10 76 MUO 4.4 19 1 1 1 Cure
15 36 IUR 7.3 34 4 6 2 Cure
19 76 rOAB 25.2 15 5 9 4 Cure
option and is appropriate for LUTD. In our study, we
categorized female LUTD into 4 types based on rstly
urodynamic and lastly clinical diagnosis, including MUO,
IUR, DV, and OAB.
For female BOO, common locations of obstruction
are the bladder neck and midurethral. Bladder neck
obstruction is usually treated by an alpha-adrenergic
antagonist or transurethral incision bladder neck. On
the other hand, most MUO cases are usually treated and
respond to SNM. Soumendra et al. reported a 10-year
experience of SNM for females with urinary retention
secondary to external urethral sphincter overactivity or
Fowler’s syndrome. e overall success was 72% and
the results revealed that females with normal urethral
sphincter activity had worse outcomes than those with
an abnormal urethral sphincter activity.
8
In our study,
female BOO was diagnosed by VUDS according to the
criteria in Blaivas’s study
5
and we found 11 cases were
MUO. In total, 7 out of 11 (63.6%) MUO cases responded
to SNM and the success rate was comparable.
In our study, both IUR and DV were clinical
diagnoses because of inconclusive VUDS result, such
that they might be detrusor acontractility (DAC), DU,
BOO, or combined abnormalities. Rademakers et al.
performed a study in 18 men with DU, dened as a
measurement value less than the 25
th
percentile in the
linear interpolation of a Maastricht–Hannover nomogram,
and reported that 50% of the cases responded to SNM.
9
Chan et al. performed a study in 50 women and 19 men
with DU, dened as having a bladder contractility index
(BCI = Pdet at Qmax + 5Qmax) of less than 100, and
reported that 51% of cases had a favorable response to
the trial phase, dened by at least a 50% improvement
in symptoms, PVR, and voided volume bladder diary.
Interestingly, 6 of 18 cases with detrusor acontractility,
dened by an absent contractility with failure to empty
and absence of EMG abnormalities, had a favorable
response to the trial phase. ey concluded that patients
with preserved detrusor contractility were more likely
to respond to SNM.
10
In our study, only one of our IUR
cases successfully responded to SNM, which probably
meant this patient had enough detrusor contractility or
BOO.
Noblett et al. performed a study in patients with
OAB, conrmed on a consecutive three-day voiding diary
with a minimum of two involuntary leaking episodes
in 72 hours and/or ≥ 8 voids per day, where success
at 12 months was dened as a ≥50% improvement in
average leaks/day or ≥50% improvement in voids/day or
a return to normal voiding frequency (<8 voids/day). e
responder rate was 85% in overall OAB symptoms. Only
37% of OAB cases with UUI had complete continence.
11
In our study, 1 of our 3 OAB cases gained continence
and was cured.
A key strength of our study study is that we tried to
identify dysfunctional causes in each case by VUDS in
order to make it clear which type of LUTD would benet
from SNM. However, urodynamic diagnosis should be
a key tool to predict SNM response, as VUDS could not
be successfully performed for most cases. Because the
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test is in an unnatural setting, we even tried to perform
it in a similar way to mimic a patient’s lower urinary
tract function. Importantly, strict urodynamic criteria
for diagnosing female BOO and DU are inconclusive and
dicult to draw conclusions, so that the SNM results of
many studies highly depend on patient selection. Lastly,
the limitations of this study to note are its small sample
size and retrospective design, which prompt the need
for further research.
CONCLUSION
SNM is another option for female patients with
non-neurogenic LUTD who have failed to respond to all
conservative treatments. In our study, aer completely
excluding anatomical abnormalities, the type of LUTD
having the highest chance to respond to SNM was found
to be midurethral obstruction (MUO). For idiopathic
urinary retention (IUR) and refractory overactive bladder
(OAB), only one-third of cases responded. No voiding
dysfunction (VD) cases responded to SNM. is information
may help urologists to better select patients for SNM.
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