ARTICLE IN PRESS

Application of High-Frequency Transcutaneous Electrical

Nerve Stimulation in Muscle Tension Dysphonia Patients
With the Pain Complaint: The Immediate Effect
*Banafshe Mansuri, *Farhad Torabinezhad, †Ali Ashraf Jamshidi, ‡Payman Dabirmoghadam,
§
Behnoosh Vasaghi-Gharamaleki, and *Leila Ghelichi, *yzxTehran, Iran

Abstract: Introduction. The aim of the present study was to investigate the immediate effect of the application
of high-frequency Transcutaneous electrical nerve stimulation (TENS) in muscle tension dysphonia (MTD)
patients with the pain complaint.
Materials and methods. Thirty patients with MTD, 10 men and 20 women with a mean age of 36.40 §
5.76 years, participated in the study. The patients were randomized into two groups: (1) Treatment group
(TENS) (10 women and 5 men) and (2) Sham TENS group (10 women and 5 men). The treatment group (TENS)
received a unique 20-minute session of high-frequency TENS. The sham TENS group was treated in the same
condition as the treatment group and received a unique 20-minute session of high-frequency TENS, but no stimu-
lation was given. Auditory-perceptual assessments, acoustic voice analysis, vocal tract discomfort (VTD), and
musculoskeletal pain were used to compare the patients pre- and post-treatment.
Results. There was a significant improvement in the asthenia parameter of auditory-perceptual assessment in
the TENS group. This improvement in asthenia was significant when comparing the TENS group with the sham
TENS group. These differences in the asthenia were not significant after using Holm-Bonferroni correction. A
comparison of the VTD before and after the TENS application showed there was a significant reduction in the
severity of the symptoms (burning, tight, dry, pain, tickling, sore, irritable, and lump in the throat). When com-
paring the TENS group with the sham TENS group, improvements in burn, tight, dry, pain, and irritable items
of VTD were observed. However, after applying the Holm-Bonferroni correction, only reductions in dry and
pain items remain significantly different between the groups. After the TENS application, the pain intensity was
significantly reduced in the anterior and posterior neck, larynx, submandibular, masseter, temporal region, and
upper back. After applying the Holm-Bonferroni correction, pain intensity reduction was significant in the ante-
rior neck and larynx. When comparing the TENS group with the sham TENS group, pain intensity was reduced
significantly in the larynx of the TENS group. This difference between the two groups was not significant after
using Holm-Bonferroni correction. The pain and VTD assessments in the present study were performed using
valid and reliable self-reported scales (NMSQ-E and VTD).
Conclusion. High-frequency TENS can be used in the voice treatment program of patients with MTD. MTD
patients with pain complaint reported that their vocal tract discomfort and pain were decreased following the high-fre-
quency TENS. Notably, these positive effects were obtained after a single session of high-frequency TENS application.
Keywords: Voice−Larynx−Transcutaneous electrical nerve stimulation−Muscle tension dysphonia−Musculo-
skeletal pain.

INTRODUCTION two types of MTD. Primary MTD is detected when there is

Muscle tension dysphonia (MTD) is a pathological condition no pathological organic lesion in the vocal folds. Secondary
in which there is an increased tension in the intrinsic and MTD involves an underlying organic lesion and indicates
extrinsic laryngeal muscles.1−5 MTD may be caused by sev- muscle tension may occur as compensation for the underly-
eral factors, including psychological/personality factors and ing organic pathology.3,6 The presence of significant tension
vocal abuse/misuse, while it may also result from a patient’s in the muscles around the larynx, laryngeal rise, tightness of
attempts to compensate for an underlying disease.3 There are the (para) laryngeal muscles, reduced space of the thyrohyoid
membrane, and local tenderness during phonation and rest
Accepted for publication February 19, 2019. should also be carefully assessed in MTD patients. Subse-
From the *Department of Speech and Language Pathology, School of Rehabilita- quently, the patient should be evaluated using laryngoscopy
tion Sciences, Iran University of Medical Sciences, Tehran, Iran; yDepartment of
Physical Therapy, School of Rehabilitation Sciences, Iran University of Medical Sci- and videostroboscopy.3 Patients with MTD experience
ences, Tehran, Iran; zOtolaryngology Research Center, Tehran University of Medical hoarseness, vocal fatigue, vocal strain, voice loss, neck tight-
Science, Tehran, Iran; and the xDepartment of Basic Sciences in Rehabilitation,
School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. ness, and pain.1,6−8 The musculoskeletal pain can have
Address correspondence and reprint requests to Farhad Torabinezhad, Department adverse effects on the muscle activity around the site of the
of Speech and Language Pathology, School of Rehabilitation Sciences, Iran Univer-
sity of Medical Sciences, Mirdamad Ave, Shahnazri Ave, Nezam Alley, Tehran, IR pain9 and this fact can be very important in MTD patients.
1346886595, Iran. E-mail: torabinezhad.f@iums.ac.ir Moreover, according to clinical experiences, a large number
Journal of Voice, Vol. &&, No. &&, pp. &&−&&
0892-1997 of patients with MTD experience some physical discomfort
© 2019 The Voice Foundation. Published by Elsevier Inc. All rights reserved. in their vocal tract such as dry, burning, tickling, sore, and
https://doi.org/10.1016/j.jvoice.2019.02.009
 ARTICLE IN PRESS
2 Journal of Voice, Vol. &&, No. &&, 2019

tight sensations.3,10 Regarding the importance of these physi- patients. However, the combination of TENS with voice
cal discomforts in the evaluation and treatment process of therapy has better results in this regard. In terms of acoustic
MTD patients, the vocal tract discomfort (VTD) scale was voice analysis and auditory-perceptual evaluations, it seems
developed by Mathieson et al.3 The VTD scale consists of that TENS makes no significant improvements in these
two sections and quantifies the frequency and severity of evaluations. Conde et al15 investigated the immediate effect
physical discomforts with eight items. Although pain and of low-frequency TENS on the pain intensity, self-reported
VTD are reported by some patients with MTD,7,11−13 few symptoms, and voice quality in dysphonic women. An
treatment programs have addressed these complaints. How- acoustic evaluation and auditory-perceptual assessment of
ever, some voice therapy techniques such as laryngeal man- the voice were used to evaluate the voice quality. They
ual therapy are effective in reducing pain and VTD in MTD found that low-frequency TENS decreased pain intensity
patients.3 Recent studies suggest transcutaneous electrical and improved vocal instability in vowel /ɑ/, but TENS did
nerve stimulation (TENS) as an adjunct to voice therapy to not result in improvements in the acoustic parameters
decrease the pain and laryngeal symptoms in MTD including fundamental frequency, jitter, shimmer, and
patients.14−17 For example, Mansuri et al combined voice noise-to-harmonic ratio. Regarding the self-reported symp-
therapy with TENS and reported better results in reducing toms, the patients pointed to the positive effects of TENS
pain and VTD in MTD patients compared to voice therapy on their voice and larynx.
alone.17 Therefore, it seems that TENS can serve as an effec- Santos et al reported the effect of using low-frequency
tive adjunctive therapy to reduce pain, VTD, and tension in TENS alone or with Tongue Trills (TT) in women with vocal
patients with MTD. fold nodules.14 They assessed patients’ laryngeal configura-
This technique, which has recently been used in voice tion with videolaryngoscopy and made judgments based on a
therapy, is rooted in electrotherapy and is abundantly used form that included three parameters: lesion size, the involve-
by physiotherapists.16,18,19 TENS is a safe, simple, noninva- ment of the laryngeal vestibule, and glottal gap. They found
sive, inexpensive, and nonpharmacological method that has that the use of TENS alone or with TT had a positive effect
been used to relieve pain for over 30 years in European on glottic closure. They reported phonation comfort
countries.14,20,21 TENS uses percutaneous electrodes to improvement in patients based on the self-reported vocal
transmit waveforms through the skin to stimulate large effort determined by the visual analog scale. In addition, they
diameter nerve fibers. This stimulation triggers central found that improvement in voice quality was observed only
inhibitory systems, which produce analgesia and reduce when TENS was combined with TT. Regarding the acoustic
pain and tension.14,16,19,22 TENS also reduces fatigue and parameters (fundamental frequency, jitter, and shimmer),
can help relax muscles and cause better vascularity.14 The there were no significant differences between the two treat-
supraspinal, spinal, and peripheral mechanisms can be the ment groups.14 Silverio et al investigated the effectiveness of
physiological underlying causes of analgesia induced by the low-frequency TENS in patients with vocal nodules.16 They
TENS.23 Regarding the spinal mechanism, Melzack and assessed the frequency and intensity of musculoskeletal pain,
Wall24 proposed the gate control theory of pain. According vocal/laryngeal symptoms, and the vocal register. After 12
to this theory, TENS causes local inhibitory circuits in the sessions of TENS, they observed that TENS decreased the
dorsal horn of the spinal cord which is related to the stimu- pain frequency and intensity in the shoulder and posterior
lation of large diameter afferent Aa and Ab fibers, thus neck. Also, they observed a reduction in some of the laryn-
changing nociceptive fibers responses.25 Moreover, TENS geal and vocal symptoms, such as effort to speak and high
can cause rhythmic muscle contractions by stimulating pitched voice. TENS also improved vocal strain.16
motor nerves and these rhythmic contractions can increase To sum up, the previous studies have shown the positive
vascularity and improve muscle relaxation.26 results of long-term and immediate effects of low-frequency
There are two important types of TENS used in electro- TENS on dysphonia. However, the positive effects of high-
therapy: high-frequency (>50 Hz) and low-frequency frequency TENS are also reported in other conditions such
(<10 Hz) TENS.19,27 These two types of TENS act as post-operative pain,30 head and neck cancer patients,31
through different mechanisms in spite of similar effects knee osteoarthritis,32 and primary dysmenorrhea19; never-
and resultant analgesia.28 Low-frequency TENS can cause theless, all of the mentioned studies in dysphonic patients
muscle contractions, while the creation of buzzing and/or used low-frequency TENS. Application of various types of
paraesthesia over the area of TENS application is the mech- TENS with different frequencies may help to the better use
anism of high-frequency TENS action.22 Given that the of TENS in the voice researches. So, further studies are
mechanism and function of low-frequency and high-fre- needed to evaluate the effects of high-frequency TENS in
quency TENS are different, it seems that the type of fre- dysphonic patients.9 The present study aimed to investigate
quency used in the TENS method can affect the results of the immediate effect of the application of high-frequency
its application.24 However, Recent studies have only exam- TENS in MTD patients with the pain complaint.
ined the effects of low-frequency TENS on dysphonic Based on the previous researches have shown that both
patients.14−16,29 These studies suggested that low-frequency high-frequency and low-frequency TENS could reduce pain in
TENS with or without voice therapy techniques can help different conditions and that low-frequency TENS could posi-
reduce pain and self-reported symptoms in dysphonic tively affect self-reported pain and VTD, auditory-perceptual
 ARTICLE IN PRESS
Banafshe Mansuri, et al High-Frequency TENS for Muscle Tension Dysphonia 3

parameters, and acoustic characteristics in patients with voice completed an informed consent form. Also, there was no
disorders. Thus, we hypothesized that one therapy session of charge for the treatment of the participants.
high-frequency TENS will result in the reduction of self-
reported pain and self-reported physical discomfort in the
Outcome measures
vocal tract of MTD patients when compared to a sham TENS
Auditory-perceptual assessment
group. However, it is difficult to comment on the effects of
We used the Grade, Roughness, Breathiness, Asthenia, and
high-frequency TENS on auditory-perceptual and acoustic
Strain (GRBAS) scale for the auditory-perceptual assess-
parameters because previous studies have reported contradic-
ment. The GRBAS scale, introduced by the Japan Society
tory results in this regard.
of Logopedics and Phoniatrics, is widely used in auditory-
perceptual assessments. The running speech of patients was
rated by two speech-language pathologists with more than
METHOD
five years of experience in the field of voice therapy. The
Participants
raters were blind to the purpose and procedure of the study.
A total of 30 MTD patients with the pain complaint partici-
The pretreatment and posttreatment voice samples of each
pated in the study. The patients included 20 women and 10
patient were given to raters independently in a quiet room for
men with a mean age of 36.40 years and a standard deviation
assessment using the GRBAS scale. The GRBAS scale uses a
(SD) of 5.76 years. The patients were recruited from the Ear,
4-point Likert scale with the following values: 0 = normal or
Nose, and Throat Department of the Amir Alam Hospital in
absence of impairment, 1 = slight impairment, 2 = moderate
Tehran, Iran. A complete case history, laryngovideostrobo- impairment, and 3 = severe impairment.33 Both inter-rater
scopy and musculoskeletal evaluation, were conducted to
and intra-rater reliability were calculated for auditory-percep-
verify the MTD diagnosis before the patients were recruited
tual assessment. To calculate the intra-rater reliability, 20%
into the study. The MTD diagnosis procedure was performed
of the voice samples were randomly re-evaluated.
for each participant by an otolaryngologist and an experi-
enced speech-language pathologist. Before acceptance into
the study, all participants were evaluated by an otolaryngolo- Instrumentation and voice samples
gist and determined to have normal speech and language, The voice samples were collected in a sound-treated room at
and no history of neurological problems, hearing defects, the Speech and Language Pathology Department of the
velopharyngeal incompetency, previous laryngeal surgery, Iran University of Medical Sciences, Tehran. Voice samples
hormone or thyroid deviation, or vascular or cardiologic dis- of running speech and sustaining the vowel /ɑ/ were
orders. Participants were excluded if they had an acute or recorded using a Zoom H5 handy digital recorder with
chronic upper respiratory infection at the time of the study. microphone capsule included with the H5 provides two
Also, patients with the previous experience of TENS treat- matched unidirectional condenser microphones set at a 90
ment were excluded. degree angle (Zoom Corporation, Tokyo, Japan) that was
The patients who met the inclusion criteria were randomly placed on a stand at a distance of 10 cm in front of the
allocated into two groups: (1) Treatment group (TENS); (2) patient’s mouth. The voice samples were recorded with a
Sham TENS group. For group allocation, each participant 44.1-kHz sampling frequency and 16-bit resolution. Partici-
drew a number between 1 and 30: odd numbers were pants were instructed to sustain the vowel /ɑ/ three times at
assigned to treatment group and even numbers were assigned their habitual pitch and loudness for at least 5 seconds. The
to sham TENS group. The treatment group was composed final (third) repetition of the vowel was used for analysis34;
of 10 women and 5 men aged 28-45 years (35.93 § 5.78). The the first and final seconds of the sample were removed and
sham TENS group comprised of 10 women and 5 men aged the middle 3 seconds were used for acoustic analysis. To
25-45 years (36.87 § 5.91). The treatment group received a obtain a sample of their running speech, we asked partici-
unique 20-minute session of high-frequency TENS. Like the pants to count from 1 to 20.
treatment group, the sham TENS group received a unique Acoustic voice analysis was performed using Praat soft-
20-minute session of TENS while the stimulator device was ware (version 6.0.23; University of Amsterdam., Amster-
turned off and no stimulation was given. All participants dam, Netherlands). Sustaining the vowel /ɑ/ was used to
were assessed for outcome measures before and after the acoustic voice analysis. The acoustic parameters that were
treatment. These outcome measures included an auditory- investigated included the F0, jitter (%), shimmer (%), and
perceptual assessment (GRBAS), acoustic voice analysis, the harmonics-to-noise ratio (HNR) (dB).
VTD scale, and musculoskeletal pain evaluation.

Self-reported symptoms
Ethical consideration The Persian Vocal Tract Discomfort (VTDp) scale was used
The present study was approved by the Ethics Committee to assess the self-reported symptoms of the participants.35
affiliated with Iran University of Medical Sciences. Partici- The VTDp scale includes two sections that quantify the fre-
pation in the study was voluntary and participants could quency and severity of throat discomfort; the frequency and
withdraw at any stage of the study. All participants severity of the symptoms are rated separately by the
 ARTICLE IN PRESS
4 Journal of Voice, Vol. &&, No. &&, 2019

participants using a 7-point Likert scale.3,35 In this study, studies that found that dysphonic women suffer from trigger
each participant completed the severity of the symptoms of points in this area.11,14,37
the VTDp scale immediately before and after the TENS and The ELPHA II 3000 muscle and nerve stimulator (Dan-
sham TENS application. The frequency section of the VTDp meter A/S, Odense, Denmark) was used for the stimulation.
scale was not used in the present study because we investi- The parameters included a symmetrical biphasic rectangu-
gated the immediate effect of TENS and sham TENS. lar pulse, 50 ms phase, and 100 Hz frequency. To ensure the
analgesic effect of the TENS, the intensity parameter of
stimulation was increased until the patients stated a strong
Musculoskeletal pain
but comfortable sensation. To evaluate the comfortable sen-
The musculoskeletal pain intensity of each participant was
sation of patients, the investigator asks the following ques-
evaluated using the Extended Nordic Musculoskeletal
tion during treatment: “Do you still feel a comfortable
Symptoms Questionnaire (NMSQ-E), which was validated
sensation?” If the patient reported an uncomfortable sensa-
in Persian.36 Pain in the anterior and posterior neck, larynx,
tion, the intensity of TENS decreased until the patient
masseter, submandibular, temporal region, upper and lower
reported a comfortable sensation.
back, shoulders, elbows, hands, and knees were evaluated
The TENS application for the sham TENS group was
using the NMSQ-E. We used A100-mm visual analog scale
identical to the TENS group, but the stimulator was turned
to measure the intensity of musculoskeletal pain; the partici-
off during the treatment.
pants were instructed to use a vertical line to mark a point
that corresponded to the pain. The left limit indicated no
pain and the right limit was equivalent to the worst possible
Statistical analysis
pain. Separate scales were used to assess each body part in
We used the Kolmogorov-Smirnov test to investigate the
which pain had been reported. Evaluation of the pain inten-
normality of the data. The normality of the data was not
sity was conducted before and immediately after the TENS
met (P < 0.05 from a Kolmogorov-Smirnov test). So, we
application.
used the non-parametric tests to compare the variables. The
Wilcoxon signed-rank test was used to within group analy-
TENS application sis and the Mann-Whitney U test was used to between
We applied high-frequency TENS in a single session for 20 group analyses. The intraclass correlation coefficient (ICC)
minutes. The patients sat in a comfortable position and was used to measure the intra-rater and inter-rater reliabil-
were asked not use their voice during the procedure. First, ity of the auditory perceptual evaluation. The significance
the patient’s skin at the application site was cleaned with level was set at P < 0.05 for all the statistical tests. Also, we
70% alcohol and conductive gel was applied before the elec- employed Holm-Bonferroni correction for multiple com-
trodes were placed. In addition, to have a better electrode parisons to avoid type I errors.38 SPSS software for Win-
adhesion in male patients, the application site was shaved dows (version 16.0, SPSS Inc., Chicago, IL) was used to
before electrode placement. The procedure for electrode perform the statistical analysis.
placement was the same as used by Santos et al13: 4 electro-
des (5 cm £ 5 cm) were placed in pairs in 2 locations. The
locations of the electrodes included the lateral center of the RESULTS
thyroid cartilage in the infrahyoid muscles and the motor Inter-rater and Intra-rater reliability of auditory-
point of the trapezius muscle on the descending fiber perceptual assessment
(Figure 1). Two electrodes were placed on the upper fibers The results of ICC calculation for inter-rater reliability of
of the trapezius region because of the results of previous the GRBAS showed that the ICC values were in the range

FIGURE 1. Electrodes placement during TENS stimulation: (a) the laryngeal area; (b) the trapezius upper fiber muscle.
 ARTICLE IN PRESS
Banafshe Mansuri, et al High-Frequency TENS for Muscle Tension Dysphonia 5

of 0.85 to 0.93. The lowest and highest ICC values were

Between Groups
related to strain and grade parameters, respectively. These

Comparison
results showed that all the parameters of GRBAS had good
or excellent ICC. Regarding the intra-rater reliability, the

P:0.332
P:0.664
P:0.294
P:0.022
P:0.276
(After)
ICC values were in the range of 0.88 to 0.95; the lowest and
highest ICC values were related to strain and breathiness
parameters, respectively.

Between Groups
Auditory-perceptual assessment

Comparison
Both TENS treatment and sham treatment resulted in
improved GRBAS rating on all the parameters. However,

Mann-Whitney U test (Between Groups Comparison). Mean § SD of before and after treatment, *, significant after Holm-Bonferroni correction, measures are reported.
(Before)

P:0.453
P:0.983
P:0.604
P:0.593
P:0.914
there was only significant improvement in asthenia in the
TENS group. Moreover, asthenia was improved signifi-
cantly in the TENS group compared to the sham TENS
group. The differences in asthenia in both within and

Abbreviations: GRBAS, grade, roughness, breathiness, asthenicity, strained; TENS, transcutaneous electrical nerve stimulation; SD, standard deviation.
between-group comparisons were not significant after

Within Groups
applying Holm-Bonferroni correction. Details about the

Comparison
GRBAS parameters before and after treatment are pre-

P Values

P:0.157

P:0.131
P:0.317
P:0.739
sented in Table 1.

P:1
Acoustic voice analysis
A comparison of the acoustic parameters showed that there

1.33 (0.67)
0.7 (0.62)
1.3 (0.81)
1 (0.68)
0.9 (0.71)
were no significant differences before and after the treat-

Comparison of Auditory-Perceptual Assessment (GRBAS) Before and After Treatment; N = 30

ment. Table 2 shows the results of the comparison of the

After
acoustic parameters.

Sham TENS
(N = 15)
Self-reported symptoms

1.46 (0.78)
0.7 (0.67)
1.46 (0.95)
1.06 (0.82)
0.93 (0.75)
The self-reported symptoms of the participants that were
based on the values of the VTDp scale are presented in
Table 3. A comparison of the VTDp scale before and after Before
the TENS application showed that there was a statistically
significant reduction in the severity of the following symp-
toms: burn, tight, dry, pain, tickling, sore, irritable, and
Within Groups

lump in the throat. After using the Holm-Bonferroni correc-

Comparison

tion, all reductions in the severity of VTD were significant

P Values

P:0.063

P:0.014
P:0.059
with a little chance of Type I error. When comparing the
P:0.18
P:0.14

TENS group with the sham TENS group, reductions were

observed in the severity of the burn, tight, dry, pain, and
irritable items of VTDp. However, after using the Holm-
Bonferroni correction, only reductions in dry and pain items
1.03 (0.89)

1 (0.98)
0.43 (0.62)
0.73 (0.99)
0.7 (.86)

were remained significant in the between-group comparison.

Wilcoxon signed-rank (Within Groups Comparison).
After

Musculoskeletal pain
(N = 15)
TENS

The pain intensity was significantly reduced in the anterior

neck, posterior neck, larynx, submandibular, masseter, tem-
0.8 (0.92)
1.3 (1.06)

0.96 (0.89)

Bold values are significant at 0.05.

1.23 (0.9)

1 (0.9)

poral region, and upper back in the TENS group. After

Before

using the Holm-Bonferroni correction, a significant reduc-

tion was observed in the pain intensity in the anterior neck
and larynx. When comparing the TENS group with the
sham TENS group, pain intensity was reduced significantly
Breathiness

in the larynx of the TENS group. However, this difference

Asthenicity
Roughness
Outcome
TABLE 1.

between the TENS group and the sham TENS group was
Strained
Grade

not significant after using Holm-Bonferroni correction.

Details about the pain intensity before and after the treat-
ment are shown in Table 4.
 6
TABLE 2.
Comparison of Acoustics Parameters Before and After Treatment in the Two Groups; N = 30
Outcome TENS Within Groups Sham TENS Within Groups Between Groups Between Groups
(N = 15) Comparison (N = 15) Comparison Comparison Comparison
P Values P Values (Before) (After)
Sustained /ɑ/ Before After Before After
F0 (Hz) 193.257 (53.27) 196.99 (53.22) P:0.211 190.51 (48.45) 190.31 (46.90) P:0.703 P:0.803 P:0.619
Jitter (%) 0.661 (0.656) 0.496 (0.267) P:0.776 0.731 (0.811) 0.728 (0.819) P:0.875 P:0.884 P:0.950
Shimmer (%) 5.64 (3.83) 3.98 (3.06) P:0.053 3.99 (2.20) 4.11 (2.00) P:0.169 P:0.309 P:0.213
HNR (dB) 18.45 (4.80) 19.88 (4.31) P:0.510 20.17 (4.18) 20.32 (2.64) P:0.821 P:0.237 P:0.373
Wilcoxon signed-rank (Within Groups Comparison).
Mann-Whitney U test (between groups comparison). Mean § SD of before and after treatment, measures are reported.

ARTICLE IN PRESS
Abbreviations: TENS, transcutaneous electrical nerve stimulation; SD, standard deviation.

TABLE 3.
Comparison of VTD Before and After Treatment in the Two Groups; N = 30
Outcome TENS (N = 15) Within Groups Sham TENS (N = 15) Within Groups Between Groups Between Groups
Comparison Comparison Comparison Comparison
P Values P Values (Before) (After)
Severity

Journal of Voice, Vol. &&, No. &&, 2019

Burning 3.80 (2.007) 1.73 (1.38) P < 0.004* 3.60 (2.61) 3.67 (2.38) P:0.564 P:0.865 P:0.025
Tight 3.13 (2.47) 1.93 (1.87) P:0.011* 3.60 (2.35) 3.53 (2.29) P:0.317 P:0.686 P:0.044
Dry 4.60 (2.09) 2.67 (1.67) P < 0.002* 4.60 (1.76) 4.53 (1.72) P:0.317 P:0.771 P < 0.004*
Pain 4.13 (2.06) 1.73 (1.53) P < 0.001* 4.07 (2.08) 3.93 (1.98) P:0.157 P:0.932 P < 0.004*
Tickling 2.20 (2.51) 1.07 (1.53) P:0.024* 0.93 (1.71) 1.07 (1.66) P:0.157 P:0.142 P:0.981
Sore 3.67 (2.35) 2.40 (2.16) P:0.01* 3.13 (2.35) 3.07 (2.28) P:0.317 P:0.498 P:0.459
Irritable 3.79 (1.76) 2.00 (1.55) P < 0.003* 3.73 (2.25) 3.87 (2.13) P:0.157 P:0.824 P:0.014
Lump in the throat 3.73 (1.94) 1.93 (1.1) P < 0.001* 3.47 (5.50) 3.33 (2.41) P:0.157 P:0.983 P:0.118
Wilcoxon signed-rank (Within Groups Comparison).
Mann-Whitney U test (Between Groups Comparison). Mean § SD of before and after treatment, *, significant after Holm-Bonferroni correction, measures are reported.
Bold values are significant at 0.05.
Abbreviations: TENS, transcutaneous electrical nerve stimulation; SD, standard deviation; VTD, vocal tract discomfort.
 Banafshe Mansuri, et al
TABLE 4.

High-Frequency TENS for Muscle Tension Dysphonia

Comparison of Pain Intensity Before and After Treatment in the Two Groups; N = 30
Outcome TENS Within Groups Sham TENS Within Groups Between Groups Between Groups
(N = 15) Comparison (N = 15) Comparison Comparison Comparison
P Values P Values (Before) (After)

ARTICLE IN PRESS
Intensity Before After Before After
Anterior neck 57.33 (40.08) 26.67 (22.57) P < 0.003* 48.67 (30.44) 45.33 (26.15) P:0.059 P:0.464 P:0.111
Posterior neck 29.33 (32.61) 15.33 (23.86) P:0.027 23.33 (23.80) 22 (23.361) P:0.157 P:0.915 P:0.196
Larynx 58 (39.85) 23.33 (20.23) P < 0.003* 54.67 (32.26) 52.67 (30.34) P:0.083 P:0.586 P < 0.007
Femor 10 (21.71) 7.33 (17.09) P:0.317 8.67 (22.94) 8 (21.11) P:0.317 P:0.725 P:0.725
Submandibular 20.67 (33.69) 9.33 (17.09) P:0.042 17.33 (29.39) 16.67 (27.94) P:0.317 P:0.882 P:0.573
Masseter 20 (28.78) 6.67 (14.96) P:0.023 18.67 (25.03) 18 (23.96) P:0.317 P:0.739 P:0.054
Temporal 26.67 (41.86) 12.67 (23.74) P:0.041 20 (32.51) 18.67 (29.24) P:0.317 P:0.833 P:0.349
Feet 12.67 (25.20) 9.33 (24.91) P:0.18 8 (19.34) 7.33 (18.69) P:0.317 P:0.634 P:0.725
Shoulders 22.67 (33.05) 16 (28.73) P:0.063 14.67 (26.42) 14 (24.72) P:0.317 P:0.581 P:0.858
Upper back 32 (33.67) 17.33 (25.48) P:0.026 24.67 (29.48) 23 (27.16) P:0.157 P:0.630 P:0.485
Lower back 18 (31.21) 15.33 (26.95) P:0.317 14.67 (30.44) 14 (29.22) P:0.317 P:0.779 P:0.823
Elbows 12.67 (23.44) 11.33 (21.99) P:0.157 12.67 (11.62) 12 (11.46) P:0.317 P:0.129 P:0.089
Hands 12 (25.69) 11.33 (20.65) P:0.655 8.67 (8.33) 9.33 (9.61) P:0.785 P:0.138 P:0.311
Knees 10 (18.51) 9.33 (14.37) P:0.705 11.33 (8.33) 12.67 (7.98) P:0.414 P:0.085 P:0.125
Wilcoxon signed-rank (Within Groups Comparison).
Mann-Whitney U test (Between Groups Comparison). Mean § SD of before and after Treatment, *, significant after Holm-Bonferroni correction, measures are reported.
Bold values are significant at 0.05.
Abbreviations: SD, standard deviation; TENS, transcutaneous electrical nerve stimulation.

7
 ARTICLE IN PRESS
8 Journal of Voice, Vol. &&, No. &&, 2019

DISCUSSION low-frequency TENS for 30 women with dysphonia and

Recent studies have investigated the effect of using TENS in found no significant improvement in F0, shimmer, jitter, or
patients with a voice disorder. Based on our knowledge, noise-to-harmonic ratio.15 Similarly, Santos et al found that a
these studies treated women with a voice disorder using single session of low-frequency TENS did not change the
low-frequency TENS. These previous studies showed that acoustic parameters in patients with vocal nodules. These
low-frequency TENS can be effective to reduce pain in dys- results were inconsistent with other studies that used electrical
phonic patients. While high-frequency TENS as another stimulation in people without voice disorders.39,40 For exam-
type of TENS application shows have different effects com- ple, studies on healthy speakers have shown that electrical
pared to low-frequency TENS. For example, some studies stimulation can cause a decrease in the sound pressure level
reported that high-frequency TENS did not cause muscle and an increase in the F0 and phonation instability. However,
tiredness and could reduce pain more quickly.27 In this studies on healthy speakers have a different design than the
study, we used high-frequency TENS to treat both women present study.39,40 The electrical stimulation used in healthy
and men with MTD with a pain complaint. The aim of the speakers’ studies is similar to that used to treat dysphagia
current study was to investigate the immediate effects of (VitalStim therapy).40 It improves the muscle weakness and
high-frequency TENS on auditory-perceptual assessment, does not cause analgesia.15 While the electrical stimulation
acoustic voice analysis, self-reported symptoms, and pain in used in the present study was TENS-type stimulation that
patients with MTD who presented with a pain complaint. reduces pain and muscle tension. The stimulation parameters
including frequency, pulse width, and intensity of stimulation
are different between these two types of electrical stimulation.
Auditory-perceptual assessment
To sum up, regarding the effects of the TENS on acoustic
In the present study, significant improvements in most of the
voice parameters, more studies are needed in this regard to
parameters of the GRBAS scale were not seen in the audi-
make more precise conclusions.
tory-perceptual assessment. Asthenia was the only parame-
ter that changed significantly after the TENS application.
Improvement in the auditory-perceptual parameters after
Self-reported symptoms
using TENS can be justified by the muscle relaxation caused
A significant reduction in the severity of all items of the
by vibration in the laryngeal and cervical musculature
VTDp scale was observed after the application of high-fre-
because we placed electrodes on laryngeal and trapezius
quency TENS. When comparing TENS with sham TENS,
areas.16 Previous studies reported conflicting results for the
improvements in burn, tight, dry, pain, and irritable items
effect of TENS on auditory-perceptual assessment.14−16,29
of VTDp were observed. These results indicated that TENS
For example, Conde et al found that TENS did not cause
can be effective in reducing self-reported symptoms of
positive changes in the perceptual parameters except for
MTD patients. Reduced muscle stiffness, fatigue, and
instability.15 Similar to the present study, the researchers
hyperactivity, caused by relaxation of the muscles, can be
used a single session of TENS. Similarly, Santos et al used
considered the possible causes of self-reported symptoms in
TENS in patients with vocal nodules and found no improve-
MTD patients because most of the MTD symptoms are due
ment in vocal quality. In another study, Guirro et al used
to the increased muscle tension.14 Our findings are in agree-
10-30-minute sessions of TENS in dysphonic women and
ment with previous studies that used low-frequency TENS
found that the treatment caused significant improvement in
in patients with voice disorders.14,15 It should be noted; we
general dysphonia, strain, breathiness, and roughness in
used VTDp scale to investigate the effects of high-frequency
spontaneous speech. However, TENS did not cause signifi-
TENS on self-reported symptoms, while other studies have
cant changes in the perceptual assessment of the production
used different scales. Despite this difference, sine all studies
of the vowel /ɑ/.29 Silverio et al reported that the application
have looked at these as self-reported symptoms, we com-
of TENS only improved the strain parameter of the percep-
pare the VTD outcomes with them. In the present study, the
tual assessment of the production of the vowel /ɑ/.16 These
reduction in VTDp items was reached in a single 20-minute
differences between studies indicate that more TENS ses-
session of high-frequency TENS. Studies by Santos et al
sions with a longer duration for each session may have better
and Conde et al reported similar results after a single session
effects on the perceptual parameters. Therefore, we suggest
of low-frequency TENS.14,15 For example, Santos et al
that future studies should compare the results of TENS used
found that vocal effort was reduced after using low-fre-
for a number of sessions of varying durations.
quency TENS,14 while Conde et al reported that TENS had
significant positive effects on symptoms regarding the lar-
Acoustic voice analysis ynx and voice as perceived by women with dysphonia.15 Sil-
In the present study, the acoustic parameters, including F0, verio et al used low-frequency TENS for 12 sessions and
jitter, shimmer, and HNR, did not change significantly after found that some symptoms, including high pitched voice
the application of high-frequency TENS in patients with and effort to speak, improved.16 In summary, it can be
MTD. These results were consistent with previous studies argued that even a single session of low-frequency or high-
that used low-frequency TENS for patients with voice disor- frequency TENS can be helpful in reducing the symptoms
ders.14,15,29 For example, Conde et al used a single session of perceived by patients with dysphonia.
 ARTICLE IN PRESS
Banafshe Mansuri, et al High-Frequency TENS for Muscle Tension Dysphonia 9

Musculoskeletal pain and self-reported pain), it was vital that the participants
Patients with voice disorders often have muscle stiffness and could not deduce they were not in the real treatment
musculoskeletal pain because of their great effort in laryn- group; if so, the full effect of placebo would be fully real-
geal and cervical muscles, which is caused by the inappro- ized. The important thing about a placebo group is that
priate use of voice behaviors.4,11,15,16,41 Several studies people receiving a placebo treatment must believe that
reported the occurrence of musculoskeletal pain in people they may be getting the real treatment. This is an area of
with various voice disorders.11,12,16,42 Despite the presence concern in TENS research in general. Therefore, there
of pain in patients with voice disorders and the negative were some risks concerning the members of the sham
impact it has on the quality of life,43 few studies have group to realize that they were not in the treatment group.
addressed musculoskeletal pain. For this reason, we investi- To reduce this risk, we excluded patients with previous
gated the effect of the TENS application on patients with experience of TENS treatment. However, it would be bet-
MTD whose main complaint was pain. The results of our ter if we used a more rigorous TENS placebo by utilizing
study showed that high-frequency TENS could reduce the a small nonclinical electrical stimulus so that participants
pain intensity in the muscles around the laryngeal and cervi- were much less likely to deduce that they were in the non-
cal regions. These areas included the anterior and posterior treatment group.23 In acoustic voice analysis, we used uni-
neck, larynx, submandibular, masseter, temporal region, directional microphones for sound recording. Considering
and upper back. A significant reduction in the pain intensity a distance of 10 cm between the microphones and the
of patients with voice disorders has also been reported in mouths of subjects in this study, the proximity effect on
previous studies that used low-frequency TENS.11,15,37 the voice samples might have been effective in acoustic
To investigate the effect of TENS on pain intensity, it is analysis.44 These limitations should be considered in future
necessary to consider three important issues. The first issue studies to better understand the effects of using TENS.
is the type of TENS (low-frequency or high-frequency) Finally, TENS as a novel therapeutic method to treat
that will be used. In studies that used low-frequency patients with voice disorders is under investigation.
TENS15,16,29 and in the current study, which used high-fre- Researchers and clinicians will continue to evaluate the
quency TENS, the pain of patients decreased. However, application of TENS for dysphonic patients. Based on the
future studies should compare the results of using high-fre- present and previous studies that used TENS for one ses-
quency TENS with the results of low-frequency TENS to sion of therapy or more, it can be said that TENS is a
make a proper and precise comment in this regard. The good complementary treatment approach to reduce pain
second issue is the duration of the TENS application. In and some physical discomfort symptoms in dysphonic
the current study and in the study by Conde et al,15 a sin- patients.14−17,29 It should be noted that TENS does not
gle session of TENS was applied; however, Silverio et al16 replace voice therapy, but it could possibly improve the
and Guirro et al29 used 12 and 10 sessions of TENS, effects of voice therapy. Also, given that the present study
respectively. The results showed that both a single session showed that high-frequency TENS could be useful in voice
and 10−12 sessions of TENS significantly reduced the pain therapy, it is suggested that future studies focus on a com-
intensity in patients with voice disorders. The third issue is parison between the effects of high-frequency and low-fre-
the electrode placement. Two methods of electrode place- quency TENS in the treatment program of patients with
ment were used in the studies. In both methods, two elec- voice disorders.
trodes were placed bilaterally on the upper fibers of the
trapezius muscle. The difference between the two methods
was the placement of the two other electrodes, which were CONCLUSION
placed in the submandibular area by Silverio et al,16 Using high-frequency TENS can be helpful in the voice
Guirro et al,29 and Conde et al15 and in the lateral center treatment program of patients with MTD. Patients with
of the larynx area by the present study and Santos et al14 MTD who presented with pain complaint reported that
The different locations of the electrodes did not make any their vocal tract discomfort and pain were decreased follow-
difference in the results; in both methods, the intensity of ing high-frequency TENS. Notably, even a single session of
pain was reduced approximately in the same areas, which high-frequency TENS can produce positive effects. Future
included the anterior and posterior neck, larynx, subman- studies are required to study the application of TENS in the
dibular, masseter, temporal region, and upper back. treatment of patients with voice disorders.

CONFLICT OF INTEREST
Limitations The authors declare that there was no conflict of interests.
The present study had some limitations. We had not used
the videolaryngostroboscopy after the TENS application.
Another limitation was that long-term assessments, such as Acknowledgments
a 1-week follow-up, were not used in this study. Given This article was part of the first author’s PhD dissertation in
that the most robust findings of the current study were speech and language pathology and was supported by Iran
related to the parameters rated by the participants (VTD University of Medical Sciences. We would like to thank the
 ARTICLE IN PRESS
10 Journal of Voice, Vol. &&, No. &&, 2019

research deputy of Iran University of Medical Sciences, as 22. Carroll D, Moore RA, McQuay HH, et al. Transcutaneous electrical
well as the patients who participated in this study. nerve stimulation (TENS) for chronic pain. Cochrane Database of Sys-
tematic Reviews. Cochrane Database Syst. Rev 2000.
23. Gibson W, Wand BM, O'Connell NE. Transcutaneous electrical nerve
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