Sexual Function Trial of Overactive Bladder: Medication Versus PTNS
Conditions: Female Sexual Dysfunction, Overactive Bladder
Sponsor: Medstar Health Research Institute

 
 
Identifiers: 
NCT03500146   Unique Protocol ID: 2016-248 
 
 
 
 
Brief Title: 
Sexual Function Trial of Overactive Bladder: Medication Versus PTNS (STOMP) 
 
 
Document Date 8/22/2017 
Uploaded 8/12/2020 
 
 

 
 
 
STOMP: Sexual function Trial of Overactive bladder: Medication versus PTNS 
 
Research Plan 
 
Specific aims: 
 
Primary aim: 
 
Aim 1: To determine if there is greater improvement in female sexual function as measured by the female 
sexual function index (FSFI) with percutaneous tibial nerve stimulation (PTNS) as compared to medical 
therapy (MT). 
Hypothesis: The investigators expect that there will be a greater improvement in overall FSFI with PTNS as 
compared to MT. 
  
Secondary aims: 
 
Aim 2: To determine if improvement in female sexual function with percutaneous tibial nerve stimulation or 
medical therapy is correlated with improvement in urinary symptoms as measured by the OAB-q questionnaire. 
Hypothesis: The investigators expect that improvement in urinary symptoms will be correlated with 
improvement in sexual function but that the difference in FSFI between groups will not be solely attributable to 
differences in urinary symptom improvement.  
 
Aim 3: To determine if changes in sexual function are greater with beta agonist medications as compared to 
anticholinergic medications. 
Hypothesis: The investigators expect that beta agonists will result in improved sexual function as compared to 
anticholinergics.  
 
Aim 4: To determine if those patients with female sexual dysfunction as defined as an overall FSFI score below 
26.5 have greater improvements than those without. 
Hypothesis: The investigators expect that patients with female sexual dysfunction will have a greater 
improvement in FSFI than those without.  
 
 
Research Strategy 
 
Significance: 
 
Female sexual dysfunction (FSD) affects approximately 45% of women with an even greater incidence 
reported in women with overactive bladder symptoms [1], [2], despite this there is a lack of FDA approved 
treatments for sexual dysfunction in this population. Female sexual function is complex and can be affected by 
pain, depression, and comorbidities as well as bowel and bladder function.  There are numerous treatments for 
women with overactive bladder defined as urinary urgency, frequency, urge urinary incontinence (UUI) and 
nocturia. These treatments include medical therapy (MT) with anticholinergics and beta agonists and 
neuromodulation via implantable sacral nerve stimulator (SNM) and percutaneous tibial nerve stimulation 
(PTNS). Sexual function, which can be measured by the Female Sexual Function Index (FSFI) has been 
shown to improve with both medical therapy and neuromodulation.  
 
Medical therapy (MT) with both oral and transdermal anticholinergics has been shown to have a positive effect 
on female sexual function in overactive bladder patients [3]–[5]. Sand et al. found improvement in responses to 
questions about sexual function in the King’s Health Questionnaire with tolterodine [5]. Hajebrahimi et al. 
showed improvement in sexual desire, arousal, vaginal lubrication and orgasm as measured by the Arizona 
Sexual Experience Scale [3]. In a randomized trial of placebo versus tolterodine, Rogers et al. showed 
improvement in the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire and found this 

 
 
improvement to be correlated with improvement in overactive bladder symptoms [4]. Beta agonist therapy is a 
relatively newer treatment for urinary urgency and there is a lack of literature regarding the effects of this 
treatment on sexual function.  
 
There are multiple hypotheses regarding the association between overactive bladder/urge incontinence and 
sexual dysfunction, including low self-esteem related to incontinence and fear of incontinence during sexual 
activity. It has been suggested that improvement in sexual function is a result of improvement in urinary 
function. This has been shown to be the case in a number of studies that have found improvement in sexual 
function correlates with improvement in urinary function [4], [14] however other studies have shown that the 
two are not correlated [6], [7], [12]. In addition to the effects of treatment on overactive bladder symptoms, 
treatments may affect sexual function in other ways. Anticholinergics may have a negative effect on sexual 
function. The human sexual response is mediated by various neurotransmitters, including acetylcholine. 
Acetylcholine’s actions on muscarinic receptors result in parasympathetic activation that leads to vasodilation 
in the erectile tissues of the clitoris, and in the lining of the vagina [15]. In fact, bethanecol has been used to 
reverse the anticholinergic properties of tricyclic antidepressants that result in sexual dysfunction [16]. 
Improved understanding of the effects of these medications on sexual function would be valuable in counseling 
patients about options for medical therapy.  
 
There are a number of hypotheses regarding the improvement in sexual function with neuromodulation. 
Neuromodulation may strengthen pelvic floor muscle tone with bulbocavernosus contraction placing pressure 
on the deep dorsal vein of the clitoris preventing venous escape and resulting in clitoral engorgement. Arterial 
flow may also be affected by neuromodulation as studies of male animals as well as human subjects have 
shown electrical stimulation of the cavernous nerve results in an erection by causing increased arterial flow in 
addition to relaxation of the cavernous muscles, and venous outflow restriction [17], [18]. In women, sacral 
nerve stimulation has been shown to result in increased vaginal pulse amplitude on vaginal plethysmography 
[19]. Understanding the comparative effectiveness of PTNS and MT may shed light on the mechanisms by 
which these treatments improve female sexual function.  
 
Neuromodulation has also been shown to have a positive impact on sexual function. There has been much 
research on the effects of neuromodulation via sacral nerve stimulator on sexual function as measured by 
FSFI. While the majority of studies show improvement in overall FSFI, there are variations with respect to 
improvement in specific domains [6]–[9]. Banakhar et al. showed improvement in overall FSFI as well as desire 
and orgasm, whereas Lombardi et al. showed improvement in overall FSFI as well as satisfaction [7], [9]. Pauls 
et al. found improvements in desire, lubrication, orgasm, satisfaction and pain, but not arousal, whereas Zahibi 
et al. showed improvement in all domains [6], [8]. These reports of SNM have all shown an improvement in 
FSFI compared to baseline. In a controlled trial comparing SNM to MT Siegel showed that among female 
patients, SNM had a greater improvement in sexual function as compared to MT [10]. This study however did 
not use a questionnaire specific to sexual function and so was unable to examine specific domains of sexual 
function.  Fewer studies have been done looking at the effect of PTNS on sexual function. Van Balken et al., in 
a study of 121 men and women examined before and after PTNS, found improvement in satisfaction, libido 
and frequency as compared to baseline [11]. Recently Musco et al. looking at 41 women who underwent PTNS 
found improvement in all domains of the FSFI [12]. This study found that improvement in urinary function did 
not correlate with improvement in sexual function. This led the authors to suggest that sexual function 
improvement might be directly related to PTNS effects rather than simply due to improvement in urinary 
symptoms [12]. A small randomized study of PTNS versus tolterodine showed a trend towards greater 
improvement with PTNS but no significant difference between groups regarding FSFI was found however the 
study was under-powered [13]. 
  
The purpose of this study is to examine the comparative effectiveness of neuromodulation via percutaneous 
tibial nerve stimulation and medical therapy with anticholinergics or beta-agonists in improving female sexual 
function. Additionally this study will assess whether improvement in sexual function is correlated with 
improvement in urinary symptoms. Furthermore the effectiveness of anticholinergics as compared to beta 
agonists with respect to changes in sexual function will be examined. Lastly the investigators aim to determine 
if patients with female sexual dysfunction have greater improvements than those without, as this may open the 

 
 
door to future studies using PTNS for the primary indication of female sexual dysfunction. Enhanced 
understanding of the effects of neuromodulation and medical therapy on sexual function may allow for 
improved patient selection and better outcomes which may lead to widespread use of neuromodulation for 
female sexual dysfunction.  
 
 
Innovation: 
 
While MT and PTNS have both been shown to improve female sexual function as compared to baseline as 
measured by the female sexual function index, there is a dearth of literature regarding their comparative 
effectiveness. A single study compared SNM to MT with sexual function examined only using the ICIQ OAB 
questionnaire which contains questions regarding sexual function but is not specific to sexual function and 
cannot tease out dysfunctions in specific domains. SNM is also more invasive than PTNS. Less is known about 
the effects of PTNS on sexual function and only a single underpowered study exists comparing PTNS to MT 
with respect to sexual function. Additionally there are conflicting results regarding whether the improvement in 
sexual function seen with PTNS and MT is associated with improvement in urinary function. If as hypothesized, 
sexual function improves to a greater extent with PTNS than with MT although both result in a similar 
improvement in urinary symptoms; it suggests that there may be additional mechanisms by which PTNS 
affects sexual function. Improved understanding of these effects may lead to clinical use of PTNS for FSD, a 
condition for which few treatments exist.  
 
Approach: 
 
This will be a prospective multi-center cohort study comparing changes in sexual function in women 
undergoing PTNS or MT for OAB/UUI. Potential subjects will be adult women presenting to a urogynecology 
clinic for symptoms of overactive bladder such as urgency and UUI.  Eligible subjects must report urinary 
urgency or urge incontinence and be recommended for treatment with medical therapy (with anticholinergic or 
beta agonist) or PTNS by the treating physician. Women meeting inclusion criteria will be asked to complete 
the validated OAB-q, FSFI, Beck Depression Inventory and a visual analog pain scale prior to therapy and then 
again after twelve weeks of therapy. Patients will also be specifically asked about the presence or absence of 
fecal incontinence and known side effects of therapy. Demographic data including age, comorbidities and 
menopausal status will be extracted from the medical record. 
 
Women meeting inclusion/exclusion criteria will be prospectively enrolled.   
- 
Women who are prescribed MT will be instructed on adherence to therapy for the twelve week duration 
of the trial. Therapy prescribed (anticholinergic versus beta agonist) will be based on shared decision-
making between the patient and the treating physician. 
- 
Women who are prescribed PTNS will undergo weekly 30 minute stimulation sessions for 12 weeks 
using a tibial nerve stimulator (Urgent® PC, Uroplasty, Minnetonka, MN, USA). The technique consists 
of stimulating the nerve by means of a 34 gauge needle electrode inserted approximately 2 inches 
cephalad and 1 inch posterior to the center of the ankle. The needle is inserted at a 60° angle pointing 
toward the head and advanced until approximately half of the needle is inserted into the leg. The lead 
wire is then connected to the stimulator and the surface electrode is placed on the inside of the arch of 
the foot of the treatment leg. The patient treatment level is identified by slowly increasing the current 
while observing the patient’s foot for a motor response (usually toe flex, fan, or twitch) and asking the 
patient to report any sensations they feel (typically mild pulsing sensation). Once treatment level is 
identified, therapy mode is initiated and continued for 30 minutes. 
 
Inclusion criteria: 
- 
Female patients greater than 18 years of age 
- 
Symptomatology of urinary urgency or urge incontinence planning to undergo MT or PTNS. Patients 
must meet a threshold bother defined by a positive response and bother of “somewhat, quite a bit, a 
great deal, or a very great deal” to questions #2, #3 or #8 on the OAB-q regarding urinary urgency and 
urgency incontinence. 

 
 
- 
Patients may have tried other medication for overactive bladder in the past but should be off therapy for 
at least one month 
- 
Patients must be currently sexually active with sexual activity within the past month and plans to 
continue for the duration of the study. Sexual activity, as defined in the FSFI questionnaire, may include 
caressing, foreplay, masturbation, and vaginal intercourse. 
- 
Patients must be willing and able to complete questionnaires in English 
 
Exclusion criteria: 
- 
Contraindications to PTNS (skin, orthopedic or anatomical limitation that could prevent placement of 
PTNS electrode, presence of pacemaker) 
- 
Contraindications to both anticholinergic and beta agonist therapy 
- 
Current symptomatic UTI within past week 
- 
Pregnant or planning to become pregnant 
- 
Prior treatment with SNM, PTNS, onobotulinum toxin A or two medications (stopped for reasons 
unrelated to side effects) 
- 
Diagnosed or suspected interstitial cystitis/painful bladder syndrome 
- 
Diagnosis of neurogenic bladder 
- 
Prolapse greater than Stage 2, pessary use or planned surgery for pelvic floor disorder during the study 
- 
Planned simultaneous treatment with both PTNS and MT 
 
 
Statistical analysis and Sample Size Calculation: 
 
The proposed study will consist of two treatment groups (MT versus PTNS). The decision to conduct a two-arm 
prospective cohort as compared to a three-arm randomized controlled trial was based on assessment of 
feasibility. The primary endpoint of the study is improvement in overall FSFI score which the investigators 
hypothesize to be greater in the PTNS group.  
 
Sample size calculations were conducted using http://clincalc.com/stats/samplesize.aspx with the primary 
endpoint of FSFI assessed as a continuous variable. Group sample sizes of 63 per group (total 126 patients) 
will be necessary to detect a clinically relevant difference of 5 points in FSFI assuming standard deviation of 10 
[13] and achieve a power of 80%, alpha=0.05. By incorporating a 10% loss to follow-up rate, the investigators 
propose to recruit 70 patients per group, with a total of 140 patients. Because approximately 45% of patients 
with OAB will have FSD as determined by an FSFI score below 26.5, the investigators aim to include up to 312 
patients in the study.  
 
Initial statistical analysis will provide descriptive statistics on the demographic and clinical characteristics of the 
study participants using means, standard deviations, median and range for continuous variables and 
frequencies and percentages for categorical variables. To examine potential differences between the study 
groups at baseline, descriptive statistics will be obtained for each group and compared statistically using two-
sample t-tests, nonparametric rank tests, chi-square and Fisher’s exact test as appropriate. All outcome 
variables will be summarized using similar methods for initial data and 12-week follow-up.   
 
Wilcoxon signed rank test will be used to assess changes in FSFI before and after treatment as the 
investigators expect the quantitative data from this to have a skewed distribution given the nature of the FSFI 
score. A subgroup analysis will be performed to determine if those patients with female sexual dysfunction as 
defined as an overall FSFI score below 26.5 have greater improvements in FSFI than those without. Mann-
Whitney U test will be used to compare FSFI scores between the MT and PTNS groups again because of the 
skewed nature of the distribution. Spearman’s correlation will be used to assess for correlation between urinary 
symptoms, and FSFI.  
 
We will analyze both intention to treat (ITT) and per protocol (treated) samples for the primary outcome.  To 
handle missing data, the investigators will employ multiple imputation models for the ITT analyses.  The 
investigators will also examine the difference between patients who complete the study and those who were 

 
 
lost to follow-up based on baseline demographic and clinical characteristics to evaluate type of missingness, 
adherence to therapy and limits to generalizability. 
 
We will conduct secondary/advanced analyses by specifying multivariate regression models of the primary 
outcome measures in order to estimate treatment differences adjusted by potential confounders. Specifically, 
multiple linear regression analyses will be used to adjust the post-treatment change scores for baseline values 
of the outcome variables as well as age, OAB-q and BMI.  These models will be estimated using cluster 
options (Intercooled Stata, command cluster) to account for the correlations between patients who are treated 
in the same hospital/site.   
 
A planned interim analysis will be conducted comparing patients receiving anticholinergics and those receiving 
beta agonists. This will be conducted once 63 patients receiving anticholinergics and 63 receiving beta 
agonists have completed the study. This will address Aim 3. A Mann-Whitney U test will be used to compare 
FSFI between patients receiving anticholinergics and beta agonists. 
 
 
Data Collection and Transmission: 
 
Potential subjects will be approached by their treating physician in the context of a private clinical visit 
regarding enrollment in the study. After discussion of the risks and benefits and obtaining written informed 
consent, each subject will be assigned a participant identification number (ID). Those patients who express 
interest but are unable to sign consent in the context of an office visit due to time constraints will be contacted 
via telephone to complete the consent process; once consent is obtained these patients will have the option of 
completing paper questionnaires which will be mailed to them or online questionnaires which they will receive 
through a secured email link. Treating physicians and investigators will monitor patients at clinic visits. Case 
report forms will be generated for each subject and completed by the investigator or study coordinator at each 
site, these will then be entered by the investigator or study coordinator into a password protected REDCap 
database with each patient identified only by ID. Patients will be asked to complete questionnaires in the 
setting of clinic visits to minimize mailings and their potential for privacy breach. Mailing of questionnaires will 
only be used if patients are unable to return to clinic for follow up; forms may also be returned via fax or secure 
email. Patients may also complete questionnaires online directly in the REDCap database. Patients will be 
encouraged to complete forms in REDCap to minimize the potential for transcription error and breach of 
privacy. For those patients who cannot mail the forms or access them online, they may be completed via 
phone with an investigator or study coordinator. Original case report forms and questionnaires will be securely 
maintained on site in a locked file cabinet within a locked office.  MedStar Washington Hospital Center will be 
the Data Collecting Center (DCC).  Copies of the case report forms and questionnaires will be forwarded by 
courier or fax to the DCC with participant ID number visible and personal information obscured. The following 
interim data will be monitored via review of the database at scheduled six-month intervals by the PI: accrual 
rate, patient adherence, adverse events and accuracy and completeness of the data.  
 
 
 
Study Timeline: 
 
Intake 
Visit 
Day 0 
12 weeks 
Assessment for eligibility 
X 
 
 
Discussion of symptoms and 
decision regarding treatment 
X 
 
 
Informed consent 
X 
 
 
Medical history 
X 
 
 
OAB-q 
 
X 
X 
Beck Depression Inventory 
 
X 
X 
Visual analog pain scale 
 
X 
X 
FSFI 
 
X 
X 

 
 
Follow up medical history 
 
 
X 
 
Potential Difficulties: 
 
There may be difficulty in recruiting patients for this study as patients may not be sexually active or may think 
discussion of sexual function is taboo. In order to account for this, the study will be a multi-center trial 
organized through the American Urogynecological Society-Society of Gynecologic Surgeons Fellows Pelvic 
Research Network (AUGS-SGS FPRN) to have a greater population from which to recruit patients. This project 
was submitted and accepted for presentation at the AUGS-SGS FPRN project proposal meeting. The FPRN is 
a fellow-run multi-center research network created to enable fellows to conduct multi-center pelvic floor 
research projects. At the meeting, which was held during the annual AUGS meeting on September 28th 2016, 
multiple sites demonstrated interest and the network decided to undertake the project. All participants within 
the Fellows Pelvic Research Network are based at academic institutions with sufficient volume to support 
fellowship training in Female Pelvic Medicine and Reconstructive Surgery. The investigators are currently 
planning to recruit patients at MedStar Franklin Square Medical Center, Indiana University, Oklahoma 
University and UT Southwestern Medical Center in addition to MedStar Washington Hospital Center. 
 
There may also be difficulty in adherence to treatment as patients may develop side effects to medical therapy 
or difficulty in adhering to the weekly schedule for PTNS causing them to stop treatment, these patients will be 
analyzed with intent to treat analysis. Patients who choose to stop therapy will be asked to fill out completion 
questionnaires at the time they inform their physician that they would like to stop treatment. 
 
Patients who undergo PTNS often are MT failures thus they may have higher OAB baseline scores and 
possibly more sexual dysfunction, as patients and their physicians choose treatment in this study, this cannot 
be controlled for. However, there are many patients in our practice who choose to pursue PTNS as initial 
treatment as well as patients who choose to pursue MT with a second medication after trying a first. By 
excluding patients who have failed treatment with two prior medications (stopped unrelated to side effects), the 
investigators aim to minimize differences between groups.  
 
 
Budget:  
Grant funding in the amount of $7,500 has been received from the Sexual Medicine Society of North America, 
additional grant applications are pending for grants from the International Society for the Study of Women’s 
Sexual Health and the Society of Women in Urology.  
 
Category 
Item Total 
Research coordinator support for an estimate 
50 hours at $45 per hour 
$2,250  
$20 gift card for participants to complete all 
questionnaires  
$6,240  
Photocopying of questionnaires  (0.10/page x 
100 pages per patient) 
$3,120  
Postage for patient questionnaires and secure 
transmission via fax from off-sites $1.25 per 
off-site patient 
$125  
Statistical support $125/hour for 10 hours 
$1,250  
Travel to SUFU meeting 
$2,000  

 
 
Total 
$14,985  
 
Patients and their insurance will be responsible for the cost of treatment whether they are in the MT or PTNS 
arm.  
 
 
References: 
 
[1] 
R. Lewis, K. Fugl-Meyer, G. Carona, and et al, “Definitions/epidemiology/risk factors for sexual factors 
for sexual dysfunction,” J Sex Med, vol. 7, pp. 1598–1607, 2010. 
[2] 
C. Shaw, “A systematic review of the literature on the prevalence of sexual impairment in women with 
urinary incontinence and the prevalence of urinary leakage during sexual activity,” Eur Urol, vol. 42, pp. 432–
440, 2002. 
[3] 
S. Hajebrahimi, A. Azaripour, and H. Sadeghi-Bazargani, “Tolterodine Immediate Release Improves 
Sexual Function in Women with Overactive Bladder.,” J Sex Med, vol. 5, no. 12, pp. 2880–2885, 2008. 
[4] 
R. Rogers, G. Bachmann, Z. Jumadilova, and et al, “Efficacy of tolterodine on overactive bladder 
symptoms and sexual and emotional quality of life in sexually active women,” Int Urogynecol J, vol. 19, p. 
1551, 2008. 
[5] 
P. Sand, R. Goldberg, R. Dmochowski, and Marilyn McIlwain, BS, Naomi V. Dahl, PharmDc, “The 
impact of the overactive bladder syndrome on sexual function: A preliminary report from the Multicenter 
Assessment of Transdermal Therapy in Overactive Bladder with Oxybutynin trial Treatment with transdermal 
oxybutynin improved sexual function,” Am J Obstet Gynecol, vol. 195, no. 6, pp. 1730–1735, 2006. 
[6] 
R. Pauls, S. Marinkovic, W. Silva, and Rooney CM, Kleeman SD, Karram MM, “Effects of sacral 
neuromodulation on female sexual function.,” Int Urogynecol J Pelvic Floor Dysfunct, vol. 18, pp. 391–395, 
2007. 
[7] 
M. Banakhar, Y. Gazwani, M. El Kelini, and et al, “Effect of sacral neuromodulation on female sexual 
function and quality of life: Are they correlated?,” Can Urol Assoc J, vol. 8, no. 11–12, pp. E762–E767, 2014. 
[8] 
N. Zahibi, A. Mourtzinos, M. Maher, and et al, “The effects of bilateral caudal epidural S2-4 
neuromodulation on female sexual function,” Int Urogynecol J, vol. 19, p. 697, 2008. 
[9] 
G. Lombardi, N. Mondaini, A. Macchiarella, A. Cilotti, and G. Popolo, “Clinical female sexual outcome 
after sacral neuromodulation implant for lower urinary tract symptom (LUTS),” J Sex Med, vol. 5, pp. 1411–
1417, 2008. 
[10] 
S. Siegel, K. Noblett, J. Mangel, and et al, “Results of a prospective, randomized, multicenter study 
evaluating sacral neuromodulation with InterStim therapy compared to standard medical therapy at 6-months 
in subjects with mild symptoms of overactive bladder,” Neurourol Urodyn, vol. 34, no. 3, pp. 224–230, 2015. 
[11] 
M. Van Balken, H. Verguns, and B. Bemelmans, “Van Balken MR, Verguns H and Bemelmans BLH. 
Sexual functioning in patients with lower urinary tract dysfunction improves after percutaneous tibial nerve 
stimulation.,” Int J Imp Res, vol. 18, pp. 470–475, 2006. 
[12] 
S. Musco, E. Lumi, A. D’Amico, and et al, “Percutaneous tibial nerve stimulation improves female 
sexual function in women with overactive bladder syndrome,” Neurourol Urodyn, vol. 33, pp. 705–707, 2014. 
[13] 
T. Eftekhar, N. Teimoory, E. Miri, and et al, “Posterior tibial nerve stimulation for treating neurologic 
bladder in women: a randomized clinical trial,” Acta Med Iran, vol. 52, no. 11, pp. 816–821, 2014. 
[14] 
D. Signorelli, C. Seitz, L. Berner, and Trenti E, Martini T, Galantini A, Lusuardi L, Lodde M, and Pycha 
A., “Impact of sacral neuromodulation on female sexual function and his correlation with clinical outcome and 
quality of life indexes: A monocentric experience,” J Sex Med, vol. 8, pp. 1147–1155, 2011. 
[15] 
A. Clayton, A. Alkis, N. Parikh, and et al, “Sexual Dysfunction Due to Psychotropic Medications,” 
Psychiatric Clinics of North America, vol. 39, no. 3, pp. 427–463. 
[16] 
M. Bernik, A. Vieira, and P. Nunes, “Bethanecol chloride for treatment of clomipramine-induced 
orgasmic dysfunction in males,” Rev Hosp Clin Fac Med Sao Paulo, vol. 59, pp. 357–360, 2004. 
[17] 
D. Quinlan, R. Nelson, A. Partin, and et al, “Quinlan DM, Nelson RJ, Partin AW et al. The rat as a 
model for the study of penile erection,” J Urol, no. 141, pp. 656–661. 
[18] 
A. Shafik, “Extrapelvic cavernous nerve stimulation in erectile dysfunction,” Andrologia, vol. 28, pp. 
151–156. 

 
 
[19] 
A. van Voskuilen, D. Oerlemans, N. Gielen, and et al, “Sexual response in patients treated with sacral 
neuromodulation for lower urinary tract symptoms or fecal incontinence,” Urol Int, vol. 88, pp. 423–430, 2012.