Transcutaneous Electrical Nerve Stimulation (TENS) in Physiotherapy

1. Sreeraj S R
TENS

2. Sreeraj S R
Definition
 Transcutaneous Electrical Nerve Stimulation (TENS) is a
method of electrical stimulation which primarily aims to
provide a degree of pain relief (symptomatic) by
specifically exciting sensory nerves and thereby
stimulating either the pain gate mechanism and/or the
opioid system.

3. Sreeraj S R
Mechanism of Action
 Possible Pain-Relieving Mechanisms;
 Activation of ‘pain-gating’ mechanisms.
 Stimulation of the descending pain suppression system
and endogenous opiate mechanisms.
 The Central Biasing Theory
 Removal of the substances which stimulate pain nerve
endings from within the damaged area

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Primary afferent fibres
4/4/2020

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Ascending Pain Pathway
 The spinothalamic tract:
transmits signals that are
important for pain localisation.
 The spinoreticular tract:
This pathway is involved in
the emotional aspects of pain.
The major role of these fibers
is thought to be general
arousal rather than sensory
discrimination per se
4/4/2020
DRG: Dorsal Root Ganglion,
PAG: Periaqueductal Grey Matter

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Inhibition of pain transmission
 Gate control theory of pain
 The gate control theory of pain
was proposed by Melzack and
Wall in 1965
 It describe a process of inhibitory
pain modulation at the spinal cord
level.
 By activating Aβ fibres with
tactile, inhibitory inter neurones
in the dorsal horn are activated
leading to inhibition of pain
signals

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Inhibition of pain transmission
 Descending inhibition
 The Periaqueductal Grey (PAG) in
the midbrain and the Rostral
Ventromedial Medulla (RVM) are
involved.
 These centres contain high
concentrations of opioid receptors
and endogenous opioids.
 Descending pathways project to the
dorsal horn and inhibit pain
transmission.
 These pathways are monoaminergic,
which modulate the serotonin,
dopamine, norepinephrine, and/or
histamine neurotransmitter systems
in the brain.
4/4/2020

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Opiate-mediated control
 Endogenous opioids
 Endorphins
 Dynorphins
 Enkephalins
 Neurophysiology background:
 The brain can secrete its own analgesic substance such
as endorphins to modulate pain.
 Endorphins are neuropeptides that act on the CNS and
peripheral nervous system to reduce pain.
 They have the similar pharmacological effect as
morphine.

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Parameters used for TENS
 Waveforms
 Frequency or Rate
 Pulse width or Duration
 Amplitude or Intensity

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Wave forms
 Square / rectangular
 Instantaneous rise
 Less skin irritating as
approaches sine wave
form
 For nerve damage
associated with pain
pathology
 For hypersensitive and
chronic pain patients
 Delayed, long-lasting
analgesia
Triangular / spike
 Rapidly rising, but not
instantaneous
 More skin irritating
therefore requires
frequent movement of
electrodes or shorter
treatment times to avoid
skin irritation
 For acute pain or resistant
tissue
 Immediate, short lasting
pain relief
4/4/2020

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Frequency or Rate
 High Frequency (80-120):
 Large myelinated fibers respond effective > 100Hz
 Immediate relief of pain
 Acute pain
 Low Frequency (1-20):
 Small unmyelinated fibers respond effectively at <100Hz
 Increase endorphin production, thus analgesia following stimulation
 Chronic pain

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Pulse width or Duration
Pulse width Indications
50μs Large myelinated fibers (sensory
touch)
100 - 150μs Normal neuromuscular system
200 μs Small myelinated fibers
200 – 300 μs Patients with neurological damage

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Amplitude or Intensity
 TENS units intensity ranges form 1 mA to 100 mA
 TENS is only effective when the patient actually feels
the stimulus
 Patients need to increase the intensity when the body
accommodates to the stimulus (when they don’t feel the
stimulation anymore)
 Dying batteries can cause fading intensities

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Types of TENS
 Conventional TENS or High Frequency TENS
 Acupuncture-like TENS (AL-TENS) or Low Frequency TENS
 Brief TENS or Intense TENS
 Burst TENS
 Modulated TENS or Modified TENS

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Conventional or High TENS
 Frequency – 50 Hz to 100 Hz
 Pulse Width – 20 μs to 60 μs
 Intensity – (0 mA to 30 mA).
 The intensity until a prickling or tingling sensation is felt.
 Principle –Presynaptic inhibition by pain gate
mechanism by stimulating Aα and Aβ fibres.
 Duration – 30 to 60 minutes once or twice daily.

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Acupuncture or Low TENS
 Frequency – 1 Hz to 4 Hz
 Pulse Width – 150 μs to 250 μs
 Intensity – 30 mA to 60 mA.
 applied to acupuncture points or motor points of muscle in the
segmentally related myotome.
 Principle –This stimulates the high threshold Aδ and C fibres,
which lead to release of endogenous opioids and provides further
sensory input from muscle spindle afferents (chemical theory).
 Duration – 20 to 30 minutes once a day.

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Burst TENS
 Burst TENS is a series of pulses (i.e. a train), repeated 1-
5 times a second, commonly twice.
 Each train or burst consists of a number of individual
pulses at the usual conventional TENS frequencies of 50
Hz to 100 Hz but at higher intensity.
 It combines both the conventional and acupuncture-like
TENS and
 therefore provides pain relief by both routes.

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Brief or Intense TENS
 Frequency – More than 100 Hz
 Pulse Width – 150 μs to 250 μs
 Intensity – Highest level tolerated by the patient.
 Principle –Activity in cutaneous Aδ afferents induced by
intense TENS produce peripheral blockade of nociceptive
afferent activity (Central biasing mechanism).
 Duration – 30 to 60 minutes once or twice daily.

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Modulated or Modified TENS
 In modulated TENS the pulse length, frequency, and
amplitudes can be constantly and automatically varied.
 This cyclical variation is believed to prevent adaptation of
the nerves to the current (no accommodation)
 is particularly appropriate as a variant of conventional
TENS used over long periods.

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Electrode Placement

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Electrode Placement

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The position of electrodes and electrical characteristics of TENS
when used to manage labour pain
Electrode Placement

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Electrode Placement

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Contraindication
 Someone with a pacemaker
 Someone with undiagnosed pain.
 Someone with a heart condition
 On head or neck of someone with epilepsy
 Someone with venous or arterial thrombosis or thrombophlebitis
 Someone with indwelling phrenic nerve or urinary bladder
stimulators
 Near operating diathermy device

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Contraindication
 Around the head
 On the eyes
 Over mucosal surfaces
 Using electrodes on infected skin
 Electrodes across the chest of a patient with cardiac disease
 Electrodes should not be placed near carotid artery in the
anterolateral region of the neck. There is a potential risk that
stimulation at this site might cause heart block by exciting the
vagus nerve.

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Precautions
 Areas of skin irritation, damage or lesions
 Areas with impaired sensation
 Over abdominal, lumbosacral or pelvic regions during pregnancy
other than for labor/delivery
 Tissues vulnerable to hemorrhage or hematoma
 Athletes should not be permitted to participate in sports while
under the influence of TENS analgesia
 Extreme caution is needed with patients taking narcotic
medication or who are known to have hyposensitive areas.

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Precautions
 Incompetent patients may not be able to manage the device and it
must be kept out of reach of children.
 For patients with diagnosed malignancies that have been
diagnosed as terminal, TENS can be used for pain control with
informed consent of the patient.
 Otherwise, TENS should not be used when malignancies are
present.

28. Sreeraj S R
References
1.Tim Watson. http://www.electrotherapy.org/modality/transcutaneous-electrical-nerve-
stimulation-tens
2.http://www.answers.com/topic/pain-1
3.http://www.david.curtis.care4free.net/painrev.htm
4.Transcutaneous Electrical Nerve Stimulation. McGill Lecture Notes – January 22nd, 2002
5.Mark Johnson. Transcutaneous electrical nerve stimulation (TENS). P 259-286
6.Foster A, Palastanga N. Clayton’s electrotherapy,9th edition, AITBS Publishers, pp 100- 106
7.Singh Jagmohan. Textbook of Electrotherapy, 2 edition, 2012;pp 129 – 133

29. Sreeraj S R
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