Sacral neuromodulation for the treatment of refractory urinary urge ...

American Journal of Obstetrics and Gynecology (2005) 193, 2083–7
Sacral neuromodulation for the treatment of
refractory urinary urge incontinence after
stress incontinence surgery
Neil D. Sherman, MD, a, * Margaret G. Jamison, PhD, b George D. Webster, MB, FRCS, a
Cindy L. Amundsen, MD a,b
Divisions of Urology, a Urogynecology, b Duke University Medical Center, Durham, NC
Received for publication January 14, 2005; revised June 8, 2005; accepted July 5, 2005
KEY WORDS
Sacral
neuromodulation
Interstim therapy
Overactive bladder
symptoms
Stress urinary
incontinence
Pubovaginal sling
Urinary incontinence
therapy
A variety of surgical techniques report a greater than
80% cure rate in treating urinary stress incontinence. 1,2 In
addition, surgical intervention for stress incontinence
may help the symptoms of the overactive bladder
Presented at the 31st Annual Meeting of the Society of Gynecologic
Surgeons Annual Scientific Meeting, April 4-6, 2005, Rancho Mirage, CA.
* Reprint requests: Neil D. Sherman, MD, Duke University Medical
Center, Division of Urology, DUMC 3146, Durham, NC 27710.
E-mail: neil.sherman@duke.edu
0002-9378/$ - see front matter Ó 2005 Mosby, Inc. All rights reserved.
doi:10.1016/j.ajog.2005.07.038
www.ajog.org
Objective: This study was undertaken to evaluate the response to sacral neuromodulation in
women with refractory, nonobstructive urinary urge incontinence after stress incontinence surgery.
Study design: We reviewed the medical records of women in whom sacral neuromodulation was
performed for worsening or de novo urinary urge incontinence after a stress incontinence
procedure. All patients had undergone preliminary test stimulation. Demographics, surgical and
urogynecologic history, including bladder diary and pad weight test, and urodynamic parameters
were evaluated.
Results: Of 34 women, 22 (65%) responded to the test stimulation and underwent permanent lead
implant. There was no difference between responders and nonresponders with respect to type of
stress incontinence surgery. Incontinence or urodynamic parameters were not different between
responders and nonresponders. Factors that were predictive of a positive response were women
aged less than 55 years (P = .01), the test stimulation performed within 4 years of the stress
incontinence procedure (P = .01), and evidence of pelvic floor muscle activity (P = .03).
Conclusion: Sacral neuromodulation is a viable option for the treatment of refractory urinary urge
incontinence that occurs after stress urinary incontinence surgery. Older women with no pelvic
floor activity who are remote from their incontinence surgery may have a suboptimal response.
Ó 2005 Mosby, Inc. All rights reserved.
(OAB) in women with mixed incontinence. 3,4 However,
it is estimated that de novo urinary urge incontinence
(UUI) occurs in 10% of women after stress urinary
incontinence (SUI) surgery and up to 40% of women
will have persistent UUI. 5,6
The accepted treatment algorithm for women with
postsurgical urinary frequency, urgency, and urge incontinence
is similar to that used in idiopathic OAB
and includes behavioral therapy and pharmacotherapy.
Although anticholinergic medication reduces urge

2084 Sherman et al
incontinent episodes and voiding frequency, many are
not improved significantly. 7 In the past, those with
refractory urgency, frequency, and urge incontinence
either accepted their condition or underwent sling takedown
or revision, augmentation cystoplasty, detrusor
myomectomy, or denervation procedures.
Recently, patients with intractable UUI, urgencyfrequency,
or nonobstructive urinary retention have
been reported to show improvement after undergoing
sacral neuromodulation (InterStim Continence Control
System, Medtronic, Inc, Minneapolis, MN). 8 To date,
the efficacy of sacral neuromodulation has not been
reported in women who underwent SUI surgery and
who have de novo or worsening UUI develop.
In this study, we look at the use of sacral neuromodulation
for the treatment of refractory UUI after
stress incontinence surgery. We also examine whether
demographic or pretest stimulation variables predict
a positive response to sacral neuromodulation.
Material and methods
Institutional review board approval was obtained for this
retrospective analysis. The medical records of all women
undergoing sacral neuromodulation test-stimulation between
October 2000 and September 2004 were reviewed.
Those with severe OAB symptoms, which appeared de
novo or persisted or worsened after their stress incontinence
surgery, were eligible for this study. All had been
referred to our Female Urology and Urogynecology clinic
because of the severity of their OAB symptoms and
having failed behavioral therapy, pelvic floor re-education,
and anticholinergic treatment. Their evaluation
included completion of a urogynecologic questionnaire,
a pelvic examination with assessment of pelvic floor
muscle strength based on a modified, validated pelvic
floor muscle grading system, 9 a 3-day bladder diary
recording micturition frequency, voided volumes and
incontinent episodes (IE) per day, a 24-hour pad weight
test, cystoscopy, and a video-urodynamic study. Women
with urethral obstruction, based on evidence of a retropexed
urethra on pelvic examination, poor sagital rotation
of the urethra during cystoscopy, and/or obstruction
on the micturition study underwent urethrolysis or incision
and release of their sling. Nonobstructed women
were candidates for a test stimulation because of the
severity of their symptoms and unresponsiveness to
medical and behavioral therapy.
Similar criteria were used for our study cohort as is
used when offering sacral neuromodulation in previously
studied InterStim groups. Before offering a test
stimulation, all women underwent extensive pelvic floor
re-education and had tried at least 2 anticholinergic
medications to improve their symptoms. Those women
with less than a 50% improvement in their symptoms
and still requiring the use of multiple protective pads per
day because of UUI were offered a test stimulation. The
test stimulation period lasted between 5 and 7 days and
was performed either as an outpatient procedure via a
percutaneous electrode (PNE) or a 2-stage approach as
previously described. 10,11
During the testing period, women completed a bladder
diary recording voiding frequency, voided volumes,
IE per day, severity of leakage, and number of pads
used. In addition, a 24-hour pad weight test was
collected the day before evaluation. A positive response
was defined as a 50% or more improvement in baseline
urge incontinent episodes or a 50% or more reduction in
pad weight during the testing period. All positive
responders were offered permanent implantation. Permanent
implantation consisted of a tined lead placed in
the S3 sacral foramen that was connected to a pulse
generator implanted in the fatty tissue of the buttock.
Age, time since incontinence surgery, and urodynamic
measurements, all continuous variables, were changed to
categorical variables with 2 responses (age older than 55
years and age 55 years or less) that best discriminated
between responders and nonresponders. Two-way c 2
tests were computed between these variables and responders
and nonresponders, young responders and older
responders, and older respondents and older nonresponders.
A logistic regression model was created to
find which independent variable(s) best predicted response
or nonresponse in the older age group because
there were no nonresponders in the younger age group.
Results
A total of 107 women underwent sacral neuromodulation
test stimulation between October 2000 and September
2004. Of the 107 women tested whose OAB
symptoms appeared de novo or persisted or worsened
after their stress incontinence surgery, 34 (32%) were
included in the study.
Of the 34 women in this study cohort, 22 (65%)
responded to the sacral neuromodulation test stimulation
and all had a permanent lead and pulse generator implanted.
Twelve patients (35%) did not have greater than
a 50% improvement in incontinent episodes or greater
than 50% reduction in pad weights during the testing
period and were classified as nonresponders, and therefore
were not implanted. There were no other alternative
therapies or surgical treatments offered to these 12 nonresponders.
The average age of the responders was 58 (range 35-82
years) and 66 (range 56-80 years) for the nonresponders
(Figure). There was a difference between the responders
and nonresponders with respect to age and length of time
from incontinence surgery to the test stimulation. All the
nonresponders were older than 55 years and 62% were
4 or more years from their incontinence surgery. Type
of stress incontinence surgery and whether a sling incision

Sherman et al 2085
Table I Surgical history of responders versus nonresponders
Characteristics N Responders (%) Nonresponders (%) P-value
Age O55 y 34 59.1 100.0 .01
Time since incontinence surgery (O4 y) 30 13.6 62.5 .01
Incontinence surgeries 34
PVS 8 22.7 25.0
PVS and prolapse repair 10 31.8 25.0 .95
PVS and sling incision 9 27.3 25.0
Other: 7 18.2 25.0
Burch (with repair) 3
Collagen 3
Needle suspension
PVS, Pubovaginal sling.
1
and release was performed were not statistically significant
factors between responders and nonresponders
(Table I).
Because a younger age has been previously shown to
be an independent variable for success with sacral
neuromodulation 7 and this was reproduced in our study,
we re-evaluated previously determined variables using
the age of 55 as a cutoff between the 2 groups. The only
parameter that was statistically significant between the
2 groups was that women older than 55, who responded
to sacral neuromodulation, had more IE per day than
the younger responders. All urodynamic and incontinence
symptom parameters were similar. Interestingly,
whether the woman was young or old, few responded to
sacral neuromodulation if their surgery had been
performed more than 4 years before the test stimulation
procedure (Table II).
All the nonresponders were in the group of women
older than 55 years. When one compared this older
group of responders and nonresponders, lack of pelvic
floor muscular activity best correlated with nonresponding
to sacral neuromodulation (Table III). After logistic
regression, if the woman is older than 55 years with no
pelvic floor activity, she has a 100% chance of not
responding to sacral neuromodulation in this cohort of
women (Table IV).
Comment
The incidence of OAB symptoms after SUI surgery
depends on the surgical technique used, and can be as
high as 31%, although usually less than 10%. 12-15 Even
with the newer minimally invasive approaches for stress
incontinence, the risk of OAB symptoms postoperatively
persists. In this study, 7 of the 28 slings were
placed by using a minimally invasive technique. Although
SUI may be resolved, the presence of OAB
symptoms proves to be a source of continued patient
dissatisfaction after incontinence procedures. 13,16
It is not clear why OAB symptoms sometimes occur
after stress incontinence procedures. Possible causes
Figure Age distribution of responders and non-responders.
include undiscovered preexisting detrusor overactivity,
a neurogenic dysfunction resulting from surgical interference
with autonomic bladder innervation, increased
striated urethral sphincter activity, or structural urethral
obstruction. 17-20 In the latter, sling incision and revision
or other urethrolysis procedures are considered. In these
cases, postoperative voiding symptoms (frequency, urgency,
and urge incontinence) occur in conjunction with
the finding of a retropexed urethra and/or an obstructive
voiding pattern on urodynamics. One third of the
women in our study group had undergone sling release
that had relieved obstructive voiding symptoms but
OAB symptoms had persisted. Interestingly, having had
a sling incision and release did not affect response to
neuromodulation.
The mechanism by which neuromodulation works
is not completely understood, it has been shown to be
efficacious in idiopathic refractory urge incontinence
and nonobstructive urinary retention. 6,21 It is believed
that neuromodulation treats bladder overactivity by
altering the activity and basal tone of the pelvic floor
as well as modulating the afferent signals delivered to
the spinal cord. 22 The cause of nonobstructive urinary

2086 Sherman et al
Table II Comparison of surgical, incontinence, and urodynamic
parameters between younger and older respondents
Young Older
responders responders P-
Measurements N (%) (%) value
Time since incontinence
surgery (O4 y)
20 25.0 33.3 .69
Pelvic floor muscle %2 20 37.5 41.6 .85
Prepad weight (g) O400 20 50.0 50.0 .99
Incontinence episodes
(no.) O5
20 12.5 66.7 .02
Pads/day (no.) R5 20 62.5 50.0 .58
Void volume (mL) R150 20 75.0 75.0 .99
Frequency (no. voids/
day) O10
20 50.0 50.0 .99
Pdet@Qmax
(cm H2O) O20
9 60.0 50.0 .76
Flow rate (mL/s) !12 11 57.1 50.0 .99
Presence of detrusor
overactivity
19 71.4 50.0 .36
Pdet@Qmax, Detrusor pressure (cm H2O) at maximum flow (mL/
second).
Table III Comparison of surgical, incontinence, and urodynamic
measurements for older respondents and nonrespondents
Older Older non
responders responders P-
Measurements N (%) (%) value
Time since incontinence
surgery (O4 y)
21 15.4 62.5 .03
Pelvic floor muscle %2 21 15.4 62.4 .03
Prepad weight (g) O400 21 38.5 75.0 .10
IE/day (no.) O5 21 61.5 50.0 .60
Pads/day (no.) R5 21 69.2 25.0 .05
Void volume (mL) R150 20 50.0 87.5 .09
Frequency (no.
voids/day) O10
20 50.0 37.5 .58
Pdet@Qmax
(cm H2O) O20
11 50.0 80.0 .30
Flow rate (mL/s) !12 11 60.0 33.3 .38
Presence of detrusor
overactivity
21 69.2 62.5 .75
retention is believed to be due to a primary failure of
relaxation of the striated urethral sphincter. 19,23 The
mechanism of action for neuromodulation in retention
patients is believed to be an activation of somatic
afferent axons in the sacral spinal roots causing an
inhibition of reflex pathways to the urethral outlet. This
ultimately relieves pelvic floor spasticity, releasing the
detrusor from inhibition to allow for spontaneous
voiding. 24
Table IV Nonrespondent rates for age and pelvic muscle
floor measurements
Percentage
Factor
nonresponse
Age alone
O55 y 48% nonresponse
PFM alone
PFM = 0 or 1 80% nonresponse
PFM %2 50% nonresponse
Age and PFM in combination
PFM = 0 or 1 and Age O55 y 100% nonresponse
PFM %2 and Age O55 y 71% nonresponse
PFM, Pelvic floor measurement.
In this study, the overall response to sacral neuromodulation
is similar to that which is reported by other
groups treating refractory idiopathic urge incontinence
with neuromodulation. 22 There are no pretest stimulation
urodynamic variables to predict success of sacral
neuromodulation and similarly in this cohort no urodynamic
variables seemed predictative of success. This
study duplicates our earlier results, specifically, that
younger women responded better to sacral neuromodulation.
7 In addition, the presence of pelvic floor neuromuscular
activity, evaluated by voluntarily contracting
the pelvic floor, was also found to predict a positive
response to neuromodulation in our cohort. Because the
believed mechanism of action of sacral neuromodulation
relies on afferent input from the pelvic floor, this
might explain the better response in these women
compared with those who demonstrated no voluntary
pelvic floor muscle contractile ability.
Our data show that a short duration between stress
incontinence surgery and sacral neuromodulation was
predictive of a positive response to neuromodulation in
both the younger and older groups. There may be
unidentified pathologic or neurologic bladder changes
that occur and limit success when time to intervention is
prolonged.
This is a small cohort study and findings regarding
correlation with time from surgery, pelvic floor muscle
denervation, and age need to be confirmed with a larger
cohort. Our results have led us to offer test stimulation for
sacral neuromodulation to women who have refractory
OAB symptoms after a SUI procedure. Nevertheless,
older women with no pelvic floor activity who are remote
from their incontinence surgery may be counseled to a
probable suboptimal response.
Conclusion
Response to sacral neuromodulation for the treatment
of refractory urge incontinence after SUI surgery is
comparable to its use in idiopathic urge incontinence.

Sherman et al 2087
The type of stress incontinence surgery, incontinence
parameters, and preimplantation urodynamics do not
help predict response to neuromodulation. Our study
suggests that a younger age, a shorter time from the
incontinence surgery and evidence of pelvic floor muscular
activity appear to predict a better response. Sacral
neuromodulation should be considered in women with
severe OAB symptoms after SUI surgery having failed
medical and behavioral therapy and after urethral
obstruction has been ruled out.
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