Can e-stim actually work for chronic pain conditions with a non-musculoskeletal cause?

Although Transcutaneous Electrical Nerve Stimulation (TENS) has been used as an analgesic of acute pain for many years, its use for chronic pain, especially of a non-musculoskeletal nature, has been sparing and unfortunately there remains limited evidence to support the effectiveness of TENS to mitigate chronic non-musculoskeletal pain.

Fibromyalgia (FM) is one such non-musculoskeletal condition. Patients with FM experience global, migrating chronic pain that is thought to be caused by alterations in the central nervous system or peripheral mechanisms. Changes to these mechanisms can results in abnormal pain processing, with lowered mechanical and thermal pain thresholds and altered temporal summation of pain stimuli .TENS aims to alleviate the FM symptoms of  pain and as such assist patients to develop long term management strategies. Current studies predicate the pain relief from TENS may only be of a temporary nature. For this reason self-administration devices have become common use with patients using the machines at home on a discretionary basis when pain presents.

A dichotomy exists between the ambiguity revolving around the effectiveness of TENS for pain relief of chronic conditions, and the fact TENS is considered to be the “gold standard” from a therapeutic view point. TENS can be used at varying frequencies, but the most common treatment for chronic pain interventions include, (i) a steady high frequency between 50 and 120 Hz, or (ii) bursts of a high frequency delivered at a low frequency between 1 and 4 Hz.

TENS has shown to be effective to reduce pain in FM patients, however the duration of pain relief is only maintained in the short term. FM patients can accomplish both a similar analgesic effect and pain relief duration with other means of treatment including, superficial warmth devices and sham TENS, when using comparable treatment times. Studies have shown there is a non-significant difference between TENS and sham TENS to reduce chronic pain symptoms, suggesting a placebo effect can be achieved and sustained for a similar pain relief period. TENS, sham TENS and superficial warmth are all appropriate e-stim methods that can significantly reduce chronic pain in FM patients compared to their base-line values. These e-stim modalities are self-administered, inexpensive and can be safely combined with other FM treatment options.




References

Arendt-Nielsen L, Graven-Nielsen T. Central sensitization in fibromyalgia and other musculoskeletal disorders. Curr Pain Headache Rep 2003; 7: 355–361.

Elvin A, Siosteen AK, Nilsson A, Kosek E. Decreased muscle blood flow in fibromyalgia patients during standardised muscle exercise: a contrast media enhanced colour Doppler study. Eur J Pain 2006; 10: 137–144.

Kosek E, Ekholm J. Modulation of pressure pain thresholds during and following isometric contraction. Pain 1995; 61: 481–486.

Staud R, Cannon RC, Mauderli AP, Robinson ME, Price DD, Vierck CJ, Jr. Temporal summation of pain from mechanical stimulation of muscle tissue in normal controls and subjects with fibromyalgia syndrome. Pain 2003; 102: 87–95.

Pain relief in women with fibromyalgia: a cross-over study of superficial warmth stimulation and transcutaneous electrical nerve stimulation. Monika Löfgren and Cecilia Norrbrink.

How can e-stim work to minimise pain?

Like everything to do with e-stim the theory behind how it does or could actually help minimise patient pain is controversial and open to debate. Two main theories have evolved; the Gate control theory and Opiate Mediated Control Theory. Other theories such as increased local vasodilation and a sensory analgesia effect have also been proposed. 

The Gate Control Theory

 A Theory of “pain” proposed by Ronald Mezlacxk and Patrick Wall in 1985 discussed a hypothetical gate mechanism that could open or close and exists within the spinal cord. Small nerve fibres (pain receptors) and large nerve fibres (somatosensory receptors) synapse on projection cells (P), which project up to the spinothalamic tract to the brain, and inhibitory interneurons (I) within the dorsal horn.

It is the interplay among all these connections which determines when a painful stimulus is transmitted to the brain:

1. (gate is closed) When no input comes is received, the inhibitory neuron prevents the projection neuron from sending signals to the brain.

2. (gate is closed) Normal somatosensory input occurs when there is increased large-fibre stimulation (or only large-fiber stimulation). Both the inhibitory neuron and the projection neuron are stimulated, but the inhibitory neuron prevents the projection neuron from sending signals to the brain.

3. (gate is open) Nociception (pain reception) occurs when there is increased small-fibre stimulation or only small-fiber stimulation. This inactivates the inhibitory neuron, and the projection neuron sends signals to the brain informing it of pain.

Further to this, there are also descending pathways from the brain that can ‘close the gate’ by inhibiting the projector neurons and therefore diminish pain perception.

E-stim, applies an electrical current to a painful area and as such the transmission of the

perception of pain. Small nerve fibres to the brain are inhibited by the activity of the large nerve and somatosensory nerve fibres (triggered by the electrical current), resulting in 'closing the gate' of the pain perception.

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Video sited form http://www.youtube.com/

The video will give an advanced insight into the mechanisms of the Gate Theory of Pain.

Opiate Mediated Control Theory

The human body has its own naturally occurring opiate and they act as a natural pain suppressor. Opiates include Beta-endorphins produced in the pituitary gland and enkephalins, produced in the spinal cord that bind to specific receptor sites. These natural opiates can be aroused by stimulating the sensory nerves with the electrical current produced with e-stim and thus block the perception of pain.

Other Theories

Other theories involved with the e-stim and pain philosophy are that it helps to increase vasodilation to tissues that have been injured leading to a painful trigger point which can initiate local ischemia. A further theory involves e-stim being able to stimulate acupuncture points causing a sensory analgesia effect by challenging the pain evoked nerve impulses at the different levels of the nervous system.

References

Cameron MH. Physical Agents in Rehabilitation from Research to Practice. Philadelphia: WB Saunders Company; 1999:387-390.

Cramp FL, McCullough GR, Lowe AS, Walsh DM. Transcutaneous electric nerve stimulation: The effect of intensity on local and distal cutaneous blood flow and skin temperature in healthy subjects. Arch Phys Med Rehabil 2002 Jan;83(1):5-9.

Hecox B, Mehreteab TA, Weisburg J. Physical Agents: A Comprehensive Text for Physical Therapists. East Norwalk, Conn: Appleton & Lange; 1994:299-305.

Joodaki MR, Olyaei GR, Bagheri H. The effects of electrical nerve stimulation of the lower extremity on H-reflex and F-wave parameters. Electromyogr Clin Neurophysiol. 2001 Jan-Feb;41(1):23-8.

Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965;150:1971-979.

Milne S, Welch V, Brosseau L, Saginur M, Shea B, Tugwell P, Wells G. Transcutaneous electrical nerve stimulation (TENS) for chronic low back pain (Cochrane Review). In: The Cochrane Library, 4, 2001.

An Introduction to Electroanalgesia

Electrical stimulation (e-stim) has been used as a rehabilitation tool since Socrates circa 400BC applied fish that could produce an electric shock to stiff joints in an attempt to loosen them up.

Thankfully electrical stimulation (e-stim) has come a long way since then. Currently electrotherapy is prescribed in 2 main ways:

·      Firstly, Functional Electrical Stimulation (FES) which directs an electrical current into a muscle body to entice a contraction and is employed mostly with muscle tone rehabilitation.

·     Secondly, and most importantly for chronic pain sufferer’s is Electroanalgesia such as Transcutaneous Electrical Nerve Stimulation (TENS) and Inferential Stimulation Therapy (IST) treatments. The support for these techniques is growing, based around positive results in clinical trials and anecdotal evidence pointing to their ability to mitigate pain symptoms.

This blog will concentrate on electroanalgesia and its effects on chronic pain that is produce from a non-musculoskeletal source. Unfortunately the genesis of some chronic pain can be varied, complicated or even unknown, but the debilitating effects of chronic pain have been identified and as such highlights the importance of analgesia treatement. We will uncover the theories behind e-stim and its proposed cessation of pain, by exploring the proposed gate theory and opiate mediated control mechanisms. We will also navigate through some of the latest findings and articulate the clinical research that will assist you to make an informed judgement on whether e-stim is indeed an option for you.

 

We hope this blog will arm you with the necessary information to discuss the appropriateness of e-stim as your modality of choice in the fight against chronic pain.



The safe use of any e-stim is paramount. All the necessary precautions and contraindications of using e-stim will be addressed in this blog. Understanding these treatment precautions will ensure optimal safety and effect, providing guidelines to use both within a clinical and home environment.

Examples of quadpolar interferential therapy and suction cupping

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