JRM-CC 2020; 3: 1000027

JRM–CC
VOL. 3, 2020

JOURNAL OF
REHABILITATION MEDICINE

CLINICALCOMMUNICATIONSARTICLE 1000027

ORIGINAL REPORTANALGESIA BY SACRAL SURFACE ELECTRICAL STIMULATION FOR PRIMARYDYSMENORRHOEA
Mieko YOKOZUKA, PT, PhD1, Mayumi NAGAI, PT, PhD2, Rieko KATSURA, PT, MS2 and Kayoko KENMYO, PT, MS2
Preparing Section for New Faculty of Medical Science, Fukushima Medical University, Fukushima, Japan
Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University, Sendai, Japan

1
2

Objective: To evaluate the effects of analgesia bysacral surface electrical stimulation on lower abdominal pain in women with primary dysmenorrhoea.
Design: Explorative study.
Participants: Eleven female university students,
who regularly experience difficulty in their university work due to menstrual pain, or who use analgesics for more than one day each month, were recruited.
Methods: Sacral surface electrical stimulation, 5
Hz for 15 min, was performed after the onset of
menstruation. Electrodes were placed on the skin,directly above the second and fourth sacral foramina. Visual analogue scale and degree of pain (calculated by using a low current to assess pain) were
determined before and after electrical stimulation.
Results: Visual analogue scale score and degreeof pain decreased significantly immediately after
electrical stimulation (p < 0.001). A correlation wasobserved between visual analogue scale score anddegree of pain before and after electrical stimulation (r=0.516, p < 0.001). No side-effects were observed in any participant.
Conclusion: Sacral surface electrical stimulation
may provide immediate pain relief in women withdysmenorrhoea and lower abdominal pain.
Key words: analgesia; dysmenorrhoea; pain; sacral surface
electrical stimulation.
Accepted Jan 1, 2020; Published Feb 27, 2020
JRM-CC 2020; 3: 1000027
Correspondence address: Mieko Yokozuka, Preparing Section for New
Faculty of Medical Science, Fukushima Medical University, 1 Hikarigaoka,
Fukushima City, Fukushima 960-1295, Japan. E-mail: yokozuka@fmu.
ac.jp

D

ysmenorrhoea is defined as painful menstrual
cramps of uterine origin. It is divided into primary

LAY ABSTRACT
Eleven female university students, who regularly experience difficulty performing their university work
due to menstrual pain, or who use analgesics for morethan one day each month, received electrical stimulation for relief of lower abdominal pain. Electrodes wereplaced on the skin over the lower region of the spine,
while participants were in the prone position. Stimulation was performed for 15 min at a frequency of 5 Hz.
Lower abdominal pain associated with menstruation
decreased immediately after electrical stimulation;
no side-effects were observed in any participant. For
women who do not wish to take analgesics, electrical stimulation could be an option for complementary
therapy. These findings indicate that electrical stimulation of the skin over the lower spine may provide
immediate relief of menstrual pain.

dysmenorrhoea without organic pathology, and secondary dysmenorrhoea with an identifiable pathologicalcondition. Lower abdominal or pelvic pain of primarydysmenorrhoea often lasts for 8–72 h, and is usually associated with the onset of menstrual flow (1–2).
Therapies for primary dysmenorrhoea have included
acupressure, analgesics, herbal remedies, topical heat,and transcutaneous electrical stimulation therapy (TENS)(2). Electrical stimulation therapy uses a relatively highfrequency (~120 Hz) for pain relief, applied by electrodes
to the dermatomes (3–6), lower abdomen (7–8), and lower
back (9–11). As a result, it has been reported that the timeto the next drug administration is prolonged and the pain
scale score is lowered. The effect of electrical stimulation
is suspected to be exerted through presynaptic inhibitionand endogenous opioid release.
Another method involves sacral surface electrical stimulation, in which stimulation is provided via electrodes

This is an open access article under the CC BY-NC license. www.medicaljournals.se/jrm-cc
Journal Compilation © 2020 Foundation of Rehabilitation Information. ISSN 2003-0711

doi: 10.2340/20030711-1000027

p. 2 of 5

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attached to the skin directly above the second and fourthsacral foramina (12, 13). For dysmenorrhoea, this has
been reported to reduce the thickness of the uterine muscle
layer and suppress peristaltic movement (12). However,there are no reports regarding the effects of sacral surface
electrical stimulation on pain.
Nevertheless, the following problems should be considered when evaluating the effects of electrical stimulation
for reducing pain, including menstrual pain. Althoughpain assessment by visual analogue scale (VAS) is simple,
it is easily influenced by mood and physical condition;in addition, some patients report improvement in pain
due to consideration for their therapists during evaluation of pain before and after treatment (14). As such, theperception/pain quantitative analyser represents a method
in which a weak current is used to quantitatively assess
pain, and has been used to evaluate pain associated with
peripheral neuropathy after cancer chemotherapy (15,16), post-herpetic nerve disorder (17), and low backpain (18, 19); however, it has not been used to assess
dysmenorrhoea pain.
The aim of this study was to evaluate the effects ofanalgesia by sacral surface electrical stimulation on lower
abdominal pain in women with primary dysmenorrhoea.
METHODS
ParticipantsThis research was conducted with approval from the ethics
committee of Tohoku Bunka Gakuen University (approval
number 16–23). Participants received written information
explaining the purpose of the study, and informed consent was
obtained from all participants included in the study.
The participants comprised nulliparous women between
the ages of 18 and 25 years who did not have a history ofgynaecological diseases and who were not currently undergoinghospital treatment for any disease. Participants were recruited
via posters on the university campus. Participants were selectedbased on grading and scoring of their symptoms and requirement
for analgesics (20). To examine the degree of dysmenorrhoea ofthe participants, the grade of dysmenorrhoea (none: score 0, noeffects; mild: score 1, some loss of study efficiency; moderate:
score 2, want to take some rest in bed, loss of study; severe:
score 3, in bed for more than 1 day) and use of analgesics(none: score 0: none; mild: score 1, take analgesics for 1 day;moderate: score 2, take analgesics for 2 days; severe: score 3,
take analgesics for >3 days) were confirmed by a questionnaire.
A flow chart of this study is shown in Fig. 1. Eleven female
university students (mean age 20.2 years (standard deviation(SD) 0.8) who regularly experience difficulty in their university
work due to menstrual pain, or who use analgesics for more than
one day each month, were recruited.
Study design
The study design was an explorative study, which involved
comparing pain before and after electrical stimulation. The study
duration was 3 cycles of menstruation. Lower abdominal pain
due to menstruation varies with each cycle. The examinationof pain and administration of electrical stimulation werewww.medicaljournals.se/jrm-cc

Subject recruitment, n=13
Regularly experienced difficulty in their university workorused analgesics for more than 1 day each month
Dropouts, n=2
Participants, n=11
Fig. 1. Flow chart of participant recruitment.

performed by different female physical therapists. For
participants using a commercially available analgesic drug,
examinations and interventions were performed ≥4 h after
taking the analgesics, to eliminate the influence of medication
as much as possible. The introspection report was collectedfrom participants after electrical stimulation.
Electrical stimulation
Since menstrual pain, such as lower abdominal pain, is related
to the onset of menstruation (1–2) and generally begins with theonset of menstruation (21), electrical stimulation was performed
as soon as possible after the onset of menstruation as reportedby the participants. For electrical stimulation, a low-frequency
treatment device (PULSECURE-PRO KR-7; OG Wellness
Technologies Co., Ltd, Okayama, Japan) and an adhesive
electrode (4.0×4.5 cm) were used. Electrodes were placed on
the skin, directly above the second and fourth sacral foramina,
while participants were in the prone position. Stimulation was
performed for 15 min with a pulse width of 300 µs, stimulation
frequency of 5 Hz, on-time 5 s, and off-time 5 s. Intensity was
adjusted to strong, but comfortable, as stated by the patient.
Evaluation of pain
Evaluation of pain was performed before and after stimulation.
Several of the 11 female university students reported back pain
and headache in addition to abdominal pain. In all cases, lower
abdominal pain was the main symptom; therefore, lower abdominal pain was evaluated. VAS score was used for the evaluationof pain in the lower abdomen. For the measurement of pain by
VAS, a line with a length of 100 mm was used; the left end
was “0: no pain,” while the right end was “100: the strongest
pain ever experienced”. The participants marked the position
corresponding to the pain they experienced. A perception/
pain quantitative analyser (Pain Vision PS-2100; Nipro Corp.,
Osaka, Japan) device was used to assess the participants’ pain
in a quantitative manner. The participants wore the stimulationelectrode on the inside of the forearm of their non-dominant
hand and had a hand switch in their dominant hand to reportsensation of current from the stimulation electrode. During theevaluation, the minimum current perception threshold at which
the subject felt stimulation (minimum perceived current) and theamount of current corresponding to the pain (pain equivalentcurrent) were measured, and the degree of pain was calculated(15–19). The stimulation current automatically and gradually
increased from 0 µA. The participant pressed the hand switch
when some stimulus was felt and when it was equivalent to theintensity of pain. Measurements were performed 4 times each,and the mean values of 2 measurements (except the maximum

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Therapeutic electrical stimulation for dysmenorrhoea

Table I. Characteristics of study participants

100

Before ES

Characteristics

0
2
9
0

After ES80

20.2 (0.8)
161.9 (6.7)
56.9 (9.8)

60

VAS

Age, years, mean (SD)Height, cm, mean (SD)Weight, kg, mean (SD)
Degree of dysmenorrhoea, n
None
Mild
Moderate
SevereUse of analgesics, n
None
Mild
Moderate
Severep. 3 of 5

40

20

2
1
6
2

0
-50

SD: standard deviation.

0

100

200

300

Degree of pain

and minimum values) were adopted. The degree of pain was
calculated using the following formula:
Degree of pain = 100 × ((pain equivalent current−minimum
perceived current)/minimum perceived current).
Statistical analysis
Normality tests were performed using the Shapiro–Wilk test.
VAS and degree of pain, both before and after electrical stimulation, were compared using the paired t-test and the Wilcoxon
signed-rank sum test, respectively.
Furthermore, Spearman’s correlation coefficient was calculated for all data before and after electrical stimulation, toanalyse the relationship between VAS and degree of pain.
Data were analysed using SPSS for Windows (Version 25.0;
IBM, Armonk, NY, USA). A p-value < 0.05 was considered
statistically significant.

RESULTS
Table I shows the characteristics of the 11 participants.
Except for the cycles of menstruation that could not
be measured due to the participants’ time constraints(academic work, vacation, public holiday, etc.), all othercycles were evaluated. Thus, a total of 28 cycles wereanalysed. One participant had one cycle with no menstrual
pain and was analysed in the next cycle.
The mean time from the onset of menstruation to theelectrical stimulation was 14.8 h (SD 10.8). Participantsin this study took non-steroidal anti-inflammatory
drugs (NSAIDs) as an analgesic. In 9 cycles of taking
the commercially available analgesics before electricalstimulation, the frequency of administration was 1.8
times (SD 1.4), and the time from medication to electricalstimulation was 11.4 h (SD 6.2). The change in pain before
and after electrical stimulation is shown in Table II.
Table II. Visual analogue scale and degree of pain before andafter electrical stimulation
Before ES
VAS, mm, mean (SD)51.9 (18.2)
Degree of pain,
100 × μA/μA, mean (SD) 79.4 (65.5)

After ES

Effectp-value size

β33.5 (23.3) < 0.001

0.870

0.007

41.2 (33.6) < 0.001

0.673

0.082

ES: electrical stimulation, VAS: visual analogue scale, SD: standard deviation.

Fig. 2. Correlation between visual analogue score (VAS) and degree ofpain for lower abdominal pain in primary dysmenorrhoea. Before electricalstimulation (ES) (white circle); after ES (grey circle). Correlation between
VAS and degree of pain (r = 0.516, β = 0.013, p < 0.001).

Mean VAS decreased significantly from 51.9 (SD18.2) before to 33.5 (SD 23.3) after electrical stimulation(p < 0.001, β = 0.007). Mean degree of pain decreased
significantly from 79.4 (SD 65.5) before to 41.2 (SD 33.6)
after electrical stimulation (p <0.001, β = 0.082). Afterelectrical stimulation, 6 cycles had a VAS less than 30%,
and 5 cycles had a VAS of 30% or more, but less than
50% of the VAS reported before electrical stimulation.
Moreover, 6 cycles had a degree of pain less than 30%,
and 8 cycles had a degree of pain of 30% or more, but lessthan 50% of the degree of pain reported before electricalstimulation.
A correlation was observed between VAS and degreeof pain before and after electrical stimulation (r=0.516,
p < 0.001, β = 0.013) (Fig. 2).
No side-effects were observed in any participant. As an
introductory report, some participants reported that “there
was always pain in all of the previous menstrual cycles, butthere was no pain in the cycle that came after the end of 2
cycles in which electrical stimulation was conducted” and“the pain disappeared right after electrical stimulation”.
DISCUSSION
The analgesic effects of sacral surface electricalstimulation were compared before and after stimulation,
and a significant reduction in VAS score and degree ofpain was observed.
As a common electrical stimulation method so far,electrical stimulation for primary dysmenorrhoea includes
some methods in which electrodes are attached at the levelof the T10 to L1 dermatomes, which include the uterinebase and body sense control dominant region; these arestimulated at 70–100 Hz (3–6). Painful lower abdomen(7–8) and lower back (9–11) have been reported to be
similarly stimulated at 100–120 Hz. Most reports use
relatively high frequencies, which enables reductions inscores of numerous pain scales, such as VAS, numerical

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rating scale (NRS), and McGill pain questionnaires, aswell as a reduction in the number of doses of analgesics required, and postponement of dosing intervals. In
particular, it has been reported that, although the intrauterine pressure does not decrease when electrodes areattached to the lower abdomen and lumbar region andstimulated at 70–100 Hz, the pain scale score decreases(22). High-frequency stimulation shows a pain-relieving
effect, compared with placebo stimulation; however,
low-frequency stimulation shows no pain-relieving effectcompared with placebo stimulation (23). This supports
the use of high-frequency electrical stimulation to reduce
the pain of primary dysmenorrhoea. On the other hand,
animal experiments have shown that the type of opioid
released differs, depending on the frequency (24); thus,
the continuous use of high-frequency stimulation may not
be ideal. Another study showed that electrical stimulation
was applied after lower abdominal gynaecological surgery
by using an electrode to sandwich the surgical wound site
in the lower abdomen with a mixed stimulus of 2 Hz and
100 Hz. This was reported to alleviate pain and to lower
the requirement for opioid analgesics, thus reducing theirside-effects (25). In primary dysmenorrhoea, electrodes
affixed to a painful lower abdomen at a frequency of 2
to 100 Hz have been reported to decrease NRS and theamount of ibuprofen used (26). Conventional electricalstimulation changes the perception of the pain signals,
without directly acting on uterine contraction, which isthe cause of dysmenorrhoea (22).
In contrast, the low-frequency stimulation used in thisstudy showed that uterine peristalsis was suppressed
during electrical stimulation on the sacral surface, on
magnetic resonance imaging (12), but also after electricalstimulation on transvaginal ultrasound (13). It is thoughtthat this afferent volley induced by pudendal nerve stimulation inhibited the pelvic nerve, and simultaneously
stimulated the hypogastric nerve, because anal sphincter
contraction was inspected or palpated (27). The causeof primary dysmenorrhoea is the excessive release of
prostaglandins, which cause the uterus to contract excessively, thereby causing pain. It can be inferred that theelectrical stimulation suppresses hyper-contraction of theuterus, which results in pain relief.
When menstrual pain is severe, it would be desirable
for the patient to be able to attach electrodes to the skinand perform electrical stimulation independently. For dysmenorrhoea, electrodes are typically placed on the lower
abdomen, or the dermatome. Electrodes can be easily andaccurately placed in these positions because the patient canvisually confirm their position. However, the sacral surface
electrical stimulation used in this study places electrodeson the skin immediately above the sacrum of each of theleft and right S2 and S4 vertebrae, which makes it moredifficult for the patient to visually confirm the accuracy ofthe electrode positioning. Therefore, it may be desirable
for this method to be performed by a healthcare provider.

www.medicaljournals.se/jrm-cc

This study found a correlation (r = 0.516, p < 0.001,
β = 0.013) between VAS and the assessed degree of pain
in lower abdominal pain due to dysmenorrhoea. The correlation between VAS and the assessed degree of pain has
been reported previously as r = 0.274–0.584 for peripheral
neuropathy associated with cancer chemotherapy (15,16) and r = 0.453–0.64 for post-herpetic neuropathy (17);similar results were obtained in the current study. The
stimulus current used for examination uses a rectangularpulse of 50 Hz and 300 µs to stimulate Aβ and Aδ fibres,
without exciting C fibres. Therefore, when measuring thepain response current value, it appeared that participants
were confused regarding when to press the switch. As aresult, correlation with VAS was observed, and we speculated that a quantitative evaluation should be performed
using the perception/pain quantitative analyser. VAS after
stimulation may be affected by the memory of visual
information from the VAS examination before stimulation. Some patients have reported improvements in pain
owing to consideration for their therapists after treatment(14). However, the perception/pain quantitative analyser
is a tool in which the participant does not look at the current stimulus. Instead, this method identifies the current
intensity at which the pain and the sensation of current
from the stimulation are equal. Therefore, although thisdevice is limited in use, it can be used as a quantitative
measurement of pain.
Study limitations
This study had some limitations. First, analgesia bysacral surface electrical stimulation for menstrual lower
abdominal pain had only an immediate effect. To use
the device for pain evaluation, it is necessary for theparticipants to go to the place where the device is located,
and it was not possible to perform an evaluation every
30 min or every hour after the electrical stimulation.
Therefore, we were unable to determine the sustained
effect of analgesia by electrical stimulation in this study.
Secondly, determining the effects of electrical stimulation
is difficult in controlled trials. However, comparing
the frequency of medications during menstrual periods
without electrical stimulation may further clarify theeffect of electrical stimulation. Some women desire nonpharmacological therapy, with statements such as, “I donot want to use the drug” and “I do not use the drug”. For
such women, we expect that electrical stimulation could
be an option for complementary therapy.
Further research is required into the effect immediately
after electrical stimulation and the sustained effect after
several hours or cycles of menstruation, changes in dose,and comparisons with drug therapy.
Conclusion
On performing sacral surface electrical stimulation during
menstruation on 11 female university students whoJRM–CC

Therapeutic electrical stimulation for dysmenorrhoea

presented with primary dysmenorrhoea, the VAS scoreand degree of pain decreased significantly immediately
after sacral surface electrical stimulation. Furthermore,
there was a correlation between VAS scores and degree of
pain. It is speculated that electrical stimulation provides
pain relief, and thus, this method may be useful for
immediate pain relief.
The authors have no conflicts of interest to declare.

REFERENCES
1. Proctor M, Farquhar C. Diagnosis and management of dysmenorrhoea. BMJ 2006; 332: 1134–1138.
2. Latthe PM, Champaneria R, Khan KS. Dysmenorrhoea. BMJ
Clin Evid 2011; 21: pii: 0813.
3. Dawood MY, Ramos J. Transcutaneous electrical nerve
stimulation (TENS) for the treatment of primary dysmenorrhea: a randomized crossover comparison with placebo
TENS and ibuprofen. Obstet Gynecol 1990; 75: 656–660.
4. Nakagawa A, Sakaguchi A, Harada K, Kawaguchi K,
Fujioka H. [Effect of transcutaneous electrical nerve
stimulation (TENS) for relieving menstrual pain in healthy
adult women.] J Jpn Phy Ther Assoc 2017; 44: 272–276(in Japanese).
5. Lauretti GR, Oliveira R, Parada F, Mattos AL. The new portable transcutaneous electrical nerve stimulation device was
efficacious in the control of primary dysmenorrhea cramp
pain. Neuromodulation 2015; 18: 522–527.
6. Kaplan B, Peled Y, Pardo J, Rabinerson D, Hirsh M, OvadiaJ, et al. Transcutaneous electrical nerve stimulation (TENS)
as a relief for dysmenorrhea. Clin Exp Obstet Gynecol
1994; 21: 87–90.
7. Kaplan B, Rabinerson D, Lurie S, Peled Y, Royburt M, NeriA. Clinical evaluation of a new model of a transcutaneouselectrical nerve stimulation device for the management ofprimary dysmenorrhea. Gynecol Obstet Invest 1997; 44:
255–259.
8. Lee B, Hong SH, Kim K, Kang WC, No JH, Lee JR, et al.
Efficacy of the device combining high-frequency transcutaneous electrical nerve stimulation and thermotherapy
for relieving primary dysmenorrhea: a randomized, singleblind, placebo-controlled trial. Eur J Obstet Gynecol Reprod
Biol 2015; 194: 58–63.
9. Wang SF, Lee JP, Hwa HL. Effect of transcutaneous electricalnerve stimulation on primary dysmenorrhea. Neuromodulation 2009; 12: 302–309.
10. Tugay N, Akbayrak T, Demirtürk F, Karakaya IC, Kocaacar
O, Tugay U, et al. Effectiveness of transcutaneous electrical nerve stimulation and interferential current in primarydysmenorrhea. Pain Med 2007; 8: 295–300.
11. Lundeberg T, Bondesson L, Lundström V. Relief of primarydysmenorrhea by transcutaneous electrical nerve stimulation. Acta Obstet Gynecol Scand 1985; 64: 491–497.
12. Ogura T, Murakami T, Ozawa Y, Seki K, Handa Y. Magnetic
resonance imaging of morphological and functional changesof the uterus induced by sacral surface electrical stimula-p. 5 of 5tion. Tohoku J Exp Med 2006; 208: 65–73.
13. Fujii O, Murakami T, Murakawa H, Terada Y, Ogura T,
Yaegashi N. Uterine relaxation by sacral surface electricalstimulation on the day of embryo transfer. Fertil Steril 2008;
90: 1240–1242.
14. Fujii M, Nishie H, Mizobuchi S, Goto K, Morimatsu H. [Assessment of analgesic effect of intravenous lidocaine in
the treatment of neuropathic pain using Pain Vision®, aquantitative pain measurement system.] J Japan Soc Pain
Clin 2014; 21: 124–128 (in Japanese).
15. Matsuoka T, Yoshida Y, Aisu N, Yamada T, Mogi A, Komono A,
et al. Evaluation of vascular pain in patients with colorectal
cancer receiving peripheral venous chemotherapy with orwithout oxaliplatin. Sci Rep 2019; 9: 1819.
16. Yoshida Y, Mogi A, Yamada T, Aisu N, Matsuoka T, Kojima D,
et al. Subjective and objective assessment of oxaliplatininduced peripheral neuropathy. Springerplus 2015; 4: 822.
17. Wang D, Zhang K, Han S, Yu L. PainVision® apparatus forassessment of efficacy of pulsed radiofrequency combinedwith pharmacological therapy in the treatment of postherpetic neuralgia and correlations with measurements. Biomed
Res Int 2017; 2017: 5670219.
18. Ohtori S, Kawaguchi H, Takebayashi T, Orita S, Inoue G,
Yamauchi K, et al. PainVision apparatus is effective for assessing low back pain. Asian Spine J 2014; 8: 793–798.
19. Kim J, Lee KS, Kong SW, Kim T, Kim MJ, Park SB, et al.
Correlations between electrically quantified pain degree,
subjectively assessed visual analogue scale, and the McGill
pain questionnaire: a pilot study. Ann Rehabil Med 2014;
38: 665–672.
20. Harada T, Momoeda M, Taketani Y, Hoshiai H, Terakawa N.
Low-dose oral contraceptive pill for dysmenorrhea associated with endometriosis: a placebo-controlled, double-blind,randomized trial. Fertil Steril 2008; 90: 1583–1588.
21. Ryan SA. The treatment of dysmenorrhea. Pediatr Clin North
Am 2017; 64: 331-342.
22. Milsom I, Hedner N, Mannheimer C. A comparative studyof the effect of high-intensity transcutaneous nerve stimulation and oral naproxen on intrauterine pressure andmenstrual pain in patients with primary dysmenorrhea. Am
J Obstet Gynecol 1994; 170: 123–129.
23. Proctor ML, Smith CA, Farquhar CM, Stones RW. Transcutaneous electrical nerve stimulation and acupuncture
for primary dysmenorrhoea. Cochrane Database Syst Rev
2002; CD002123.
24. Kalra A, Urban MO, Sluka KA. Blockade of opioid receptors inrostral ventral medulla prevents antihyperalgesia producedby transcutaneous electrical nerve stimulation (TENS). J
Pharmacol Exp Ther 2001; 298: 257–263.
25. Hamza MA, White PF, Ahmed HE, Ghoname EA. Effect of
the frequency of transcutaneous electrical nerve stimulation on the postoperative opioid analgesic requirement andrecovery profile. Anesthesiology 1999; 91: 1232–1238.
26. Bai HY, Bai HY, Yang ZQ. Effect of transcutaneous electricalnerve stimulation therapy for the treatment of primarydysmenorrhea. Medicine 2017; 96: e7959.
27. Yokozuka M, Namima T, Nakagawa H, Ichie M, Handa Y. Effects and indications of sacral surface therapeutic electricalstimulation in refractory urinary incontinence. Clin Rehabil
2004; 18: 899–907.

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