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Correct Electrode Placement During Sham Stimulation in Transcutaneous Auricular Vagus Nerve Stimulation

Authors:
Alper Perçin at Avrasya Üniversitesi
Alper Perçin
  • Avrasya Üniversitesi
Ali Veysel Özden at Bahçeşehir University
Ali Veysel Özden
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Abstract

Correct Electrode Placement During Sham Stimulation in Transcutaneous Auricular Vagus Nerve Stimulation
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Received: 7 January 2024, Accepted: 9 January 2024, Published: 9 January 2024
Corresponding author: Alper Percin, 1 Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Igdir University, Igdir, Türkiye.
+905452557585 alperpercin@yahoo.com
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Letter to the Editor
Med J Eur. 2024;2(2):4-5
Correct Electrode Placement During Sham Stimulation in Transcutaneous
Auricular Vagus Nerve Stimulation
Alper Percin 1, Ali Veysel Ozden 2
1 Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Igdir University, Igdir, Türkiye
2 Department of Physiotherapy and Rehabilitation, Institute of Health Sciences, Bahcesehir University, Istanbul, Türkiye
ISSN: 2995-7907 doi: 10.5281/zenodo.10473943
To the Editor,
In recent years, transcutaneous auricular vagus nerve
simulation (taVNS) has been used for pain management in
chronic musculoskeletal disorders, stimulation of increased
parasympathetic activity in autonomic nervous system
disorders, reduction of the level of inflammatory cytokines in
inflammatory rheumatological diseases, and improvement of
motor function in neurological patients. When using this
method, different electrode placement methods have been
proposed, but there are some situations that need to be
considered.
Wu et al. (1) included 92 patients with Meniere's disease in their
study. 46 patients received taVNS combined with Betashistine
treatment, while 46 patients received sham taVNS combined
with Betashistine treatment. The participants were received 12
weeks of taVNS (30 minutes each time, twice a day, five times
a week) in this study. In the intervention group, the electrodes
were placed on the simba concha and the concha in the outer
ear, whereas in the control group, the electrodes were placed in
the antihelix. As can be seen in the study by Wu et al (1), in the
control group the electrodes (anode and cathode) were placed
in such a way that the vagus nerve branches remained between
anode and cathode. In this case, it is likely that the vagus nerve
was stimulated and it would be wrong to call it placebo or sham
stimulation.
Bajd and Munih (2) investigated the effects of basic functional
electrical stimulation on surrounding tissues and found that
when a stimulating current is applied to electrodes placed on
the skin over sensorimotor structures, an electric field is
generated between the two electrodes. In this study, the effect
of the electrical current between the anode and cathode on the
nerve tissue was attempted to be more clearly explained in
Figure 1. The flow of ions along the nerve affects the
transmembrane potential and can generate an action potential.
The action potential spreads along the nerve and causes
excitation.
Figure 1. Effect of the electrical field generated by anodal and
cathodal electrodes on nerve tissue (2).
Transcutaneous electrical nerve stimulation (TENS), which has
been used for peripheral nerve stimulation for many years,
delivers electrical currents through electrodes across the intact
surface of the skin (3). TENS selectively activates peripheral
nerve fibres to produce physiological neuromodulation. In
order to achieve neuromodulation, electrodes are placed on
each side with the peripheral nerve in the centre and the nerve
cells are depolarised by the electrical field created. (4). In order
to activate of the nerve fibers with the TENS, the cathode in the
form of the current released from the electrodes placed on the
skin stimulates the axon, causing deporalization and initiating
impulse transmission. Although it is difficult to predict the
exact results of electric current related to the non-homogeneous
thickness and impedance of the skin, the electrical current is
likely to stimulate superficial cutaneous nerve fibers (5).
As a result, if anode and cathode electrodes are placed around
a region with vagus nerve branches, vagus nerve stimulation
will be a real stimulation and this cannot be called a sham
simulation. It is inevitable that the resulting electric field will
cause stimulation in the vagus nerve branches.
5
REFERENCES
1. Wu D, Liu B, Wu Y, et al. Meniere Disease treated with transcutaneous
auricular vagus nerve stimulation combined with betahistine Mesylate:
A randomized controlled trial. Brain Stimul. 2023;16(6):1576-1584.
doi:10.1016/j.brs.2023.10.0032.
2. Bajd T, Munih M. Basic Functional Electrical Stimulation (FES) of
Extremites – an Engineer's View. Technol Health Care. 2010;18(4-
5):361-369. doi:10.3233/THC-2010-0588
3. Sonwane A, Patil CY, Deshmukh GR. Design and Development of
Portable Transcutaneous Electrical Nerve Stimulation Device and Basic
Principles for the use of TENS. ICOEI. 2018; 285-287.
doi:10.1109/ICOEI.2018.8553898
4. Johnson M. Resolving Long-Standing Uncertainty about the Clinical
Efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) to
Relieve Pain: A Comprehensive Review of Factors Influencing
Outcome. Medicina. 2021; 57(4):378.
htps://doi.org/10.3390/medicina57040378
5. Johnson M. Transcutaneous Electrical Nerve Stimulation: Mechanisms,
Clinical Application and Evidence. Rev Pain. 2007;1(1):7-11.
doi:10.1177/204946370700100103
Conflicts of interest
None.
Funding source
None.
Acknowledgements
None.
ResearchGate has not been able to resolve any citations for this publication.
Resolving Long-Standing Uncertainty about the Clinical Efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) to Relieve Pain: A Comprehensive Review of Factors Influencing Outcome
Article
Full-text available
Pain is managed using a biopsychosocial approach and pharmacological and non-pharmacological treatments. Transcutaneous electrical nerve stimulation (TENS) is a technique whereby pulsed electrical currents are administered through the intact surface of the skin with the intention of alleviating pain, akin to ‘electrically rubbing pain away’. Despite over 50 years of published research, uncertainty about the clinical efficacy of TENS remains. The purpose of this comprehensive review is to critically appraise clinical research on TENS to inform future strategies to resolve the ‘efficacy-impasse’. The principles and practices of TENS are described to provide context for readers unfamiliar with TENS treatment. The findings of systematic reviews evaluating TENS are described from a historical perspective to provide context for a critical evaluation of factors influencing the outcomes of randomized controlled trials (RCTs); including sample populations, outcome measures, TENS techniques, and comparator interventions. Three possibilities are offered to resolve the impasse. Firstly, to conduct large multi-centered RCTs using an enriched enrolment with randomized withdrawal design, that incorporates a ‘run-in phase’ to screen for potential TENS responders and to optimise TENS treatment according to individual need. Secondly, to meta-analyze published RCT data, irrespective of type of pain, to determine whether TENS reduces the intensity of pain during stimulation, and to include a detailed assessment of levels of certainty and precision. Thirdly, to concede that it may be impossible to determine efficacy due to insurmountable methodological, logistical and financial challenges. The consequences to clinicians, policy makers and funders of this third scenario are discussed. I argue that patients will continue to use TENS irrespective of the views of clinicians, policy makers, funders or guideline panel recommendations, because TENS is readily available without prescription; TENS generates a pleasant sensory experience that is similar to easing pain using warming and cooling techniques; and technological developments such as smart wearable TENS devices will improve usability in the future. Thus, research is needed on how best to integrate TENS into existing pain management strategies by analyzing data of TENS usage by expert-patients in real-world settings.
View
Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence
Article
Full-text available
  • Aug 2007
•Transcutaneous electrical nerve stimulation (TENS) is a non-invasive, inexpensive, self-administered technique to relieve pain.•There are few side effects and no potential for overdose so patients can titrate the treatment as required.•TENS techniques include conventional TENS, acupuncture-like TENS and intense TENS. In general, conventional TENS is used in the first instance.•The purpose of conventional TENS is to selectively activate large diameter non-noxious afferents (A-beta) to reduce nociceptor cell activity and sensitization at a segmental level in the central nervous system.•Pain relief with conventional TENS is rapid in onset and offset and is maximal when the patient experiences a strong but non-painful paraesthesia beneath the electrodes. Therefore, patients may need to administer TENS throughout the day.•Clinical experience suggests that TENS may be beneficial as an adjunct to pharmacotherapy for acute pain although systematic reviews are conflicting. Clinical experience and systematic reviews suggest that TENS is beneficial for chronic pain.
View
Basic functional electrical stimulation (FES) of extremities: An engineer's view
Article
Full-text available
  • Nov 2010
  • Tech Health Care
The historical development of electrical stimulators producing contraction of paralyzed muscles is briefly presented. The influence of electrical stimulation parameters (amplitude of pulses, frequency, pulse duration, and duration of a pulse train) is explained. Special attention is paid to the description of the muscle recruitment curve. The phenomenon of reversed recruitment order, resulting in fatiguing of electrically stimulated muscle, is presented. The properties of surface electrodes (electrode size, polarity, resistance, and distance between electrodes) are examined. The use of surface electrodes made of metal plate or wire mesh, silicone impregnated with rubber, and conductive adhesive gel are discussed. The design of electrical stimulator circuits is also presented.
View
View
Meniere Disease treated with transcutaneous auricular vagus nerve stimulation combined with betahistine Mesylate: A randomized controlled trial
  • Jan 2023
  • BRAIN STIMUL
  • 1576-1584
  • D Wu
  • B Liu
  • Y Wu
Wu D, Liu B, Wu Y, et al. Meniere Disease treated with transcutaneous auricular vagus nerve stimulation combined with betahistine Mesylate: A randomized controlled trial. Brain Stimul. 2023;16(6):1576-1584. doi:10.1016/j.brs.2023.10.0032.