Blog 4: And in summary...

The information provided in Table 4.0 is a collaborative summary of the information we have discussed thus far outlining the use of electrical stimulation for the treatment of chronic pain. This table does not in any way provide an exclusive list for each modality of electrical stimulation as other treatment considerations may arise for different conditions and individual patients. The information regarding TENS was most extensive due to the vast amount of research available, whilst other modalities have questionable contraindications and precautions in comparison, with limited amount of evidence. At this point of our blog series, we feel it is important to reiterate that any electrotherapy agents should be avoided when the contraindications in Table 4.0 are listed. 

Table 4.0: General parameters, electrode placement, contraindications and precautions of electrical stimulation modalities studied

ESTIM	RECOMMENDED PARAMETERS	ELECTRODE PLACEMENT/SAFETY	CONTRAINDICATIONS	PRECAUTIONS
GENERAL ESTIM	Acute conditions: Low intensity, short duration Chronic conditions: Moderate-high intensity, long duration	Same size and type of electrodes used bilaterally Consistent amount of gel used over area being treated Size of electrodes: Small = increased density of current Large = decreased density of current Distance between electrodes: Small = superficial structures targeted Large = deeper structures targeted	·         Pregnancy ·         Local malignancy ·         Pacemakers ·         Epilepsy (application CI at neck) ·         Haemorrhage ·         Active Epiphysis (local) ·         Negative skin discrimination test ·         Infections ·         Unreliable/uncommunicative /unwilling patient	·         Local circulatory insufficiency ·         Devitalised tissue ·         Superficial metal ·         Open wounds ·         Individuals with high pain tolerance ·         Skin damage or irritation ·         Do not apply around the eye or testes
			EXTRA CONTRAINDICATIONS	EXTRA PRECAUTIONS
TENS	Duration: Varies depending on type of TENS and area of pain – generally is of longer duration; greater than 30mins for chronic pain Conventional: 40-150Hz, 50-100μs pulse width, low intensity* Acupuncture like: 1-4Hz, 100-400μs pulse width, high intensity* Brief-intense: >80Hz, >150μs pulse width, tolerable intensity* Burst mode: bursts <10Hz, comfortable intensity* Modulation: one or more parameters randomly modulated *intensity is determined by individual patient and their perceptions.	DO NOT PLACE ELECTRODES OVER: ·         Stomach when pregnant ·         Carotid sinus ·         Temples ·         Local malignancy ·         Open skin wounds DO NOT PLACE ELECTRODES ACROSS: ·         Heart ·         Throat ·         Cerebrum	See General Estim contraindications	TENS during the first trimester and first stage of labour has been shown to be beneficial, but only when applied over the lower back or wrist for Carpal tunnel syndrome (CTS). Caution must be used to avoid acupuncture points.
PENS	Frequency: Modulated with a combination of 2Hz, 30Hz and 100Hz. Duration: 30 minutes	See General Estim and TENS Electrode Placement/Safety	See General Estim and TENS contraindications	See General Estim and TENS precautions
CCEF	Frequency: 60kHz active wave, pulsed with 12.5Hz at a 50% duty cycle Intensity: 7V(peak to peak) AC waveform Current density: 25μA/cm2 Duration: 10 hours per day	See General Estim and TENS Electrode Placement/Safety	Limited research available. Follow contraindications of General Estim	Limited research available. Follow precautions of General Estim
TCES	Frequency: 77Hz Average pulse width: 3.3msec Duration: 30min	‘Headset’ with 3 electrodes, adjusted to fit comfortably over the patient’s cranium. Electrode placement: One electrode each side over mastoid process One electrode on forehead	Limited research available. Follow contraindications of General Estim	Limited research available. Follow precautions of General Estim
rTMS	Frequency: <1Hz (inhibitory effect) Duration: Bursts of up to 10 seconds	Stimulation over motor cortex and/or dorsolateral prefrontal cortex for chronic pain. The patient positions their chin on a stand with their forehead supported. A magnetic field is created by 2 adjoining wire coils approximately 1cm above the patient's head which is positioned so that the area to be treated is aligned with the midline of the two coils.	·         Aneurysm clips ·         Cranial implants ·         Epilepsy ·         Recent cardiovascular event ·         Increased intracranial pressure	·         Long durations can induce seizures or fainting

To conclude, the use of varying modalities of electrotherapy agents to provide analgesia for chronic pain sufferers seems promising but many gaps exist in the research. After discussion and consideration of the available evidence throughout our blog series, we have decided that there are a number of questions which remained unanswered regarding the exact perceived benefits of using electrical stimulation to treat chronic pain, but there is a benefit nonetheless. Whether the patient feels pain relief as a direct result of the electrical stimulation or rather from a placebo effect remains a topic of debate within the literature and the issue merits further investigation into the future of the research surrounding this area. Regardless, pain relief for the patient is always seen as a positive outcome and hence as an indication for the use of electrical stimulation as part of the patient’s treatment regime.

REFERENCES

Beecher, H.K. (1992). The placebo effect as a nonspecific force surrounding disease and the treatment of disease. JAMA, 179,437-440.

Cheing, G. L., & Hui-Chan, C. W. (1999). Transcutaneous electrical nerve stimulation: nonparallel antinociceptive effects on chronic clinical pain and acute experimental pain. Arch Phys Med Rehabil, 80(3), 305-312.

Cohen, I.J. (1994). A new approach to pain. Emergency Med, 6, 241-254.

Deyo, R.A., Walsh, N.E., Martin, D.C. et al. (1990). A controlled trail of transcutaneous electrical nerve stimulation (TENS) and exercise for chronic low back pain. N Engl J Med, 322, 1627-1634.

Durmus, D., Durmaz, Y., & Canturk, F. (2010). Effects of therapeutic ultrasound and electrical stimulation program on pain, trunk muscle strength, disability, walking performance, quality of life, and depression in patients with low back pain: a randomized-controlled trial. Rheumatol Int, 30(7), 901-910.

Gabis, L., Shklar, B., Baruch, Y. K., Raz, R., Gabis, E., & Geva, D. (2009). Pain reduction using transcranial electrostimulation: a double blind "active placebo" controlled trial. J Rehabil Med, 41(4), 256-261.

Ghoname, E. S., Craig, W. F., White, P. F., Ahmed, H. E., Hamza, M. A., Gajraj, N. M., et al. (1999). The effect of stimulus frequency on the analgesic response to percutaneous electrical nerve stimulation in patients with chronic low back pain. Anesth Analg, 88(4), 841-846.

Itoh, K., Itoh, S., Katsumi, Y., & Kitakoji, H. (2009). A pilot study on using acupuncture and transcutaneous electrical nerve stimulation to treat chronic non-specific low back pain. Complement Ther Clin Pract, 15(1), 22-25.

Khadilkar, A., Milne, S., Brosseau, L., Wells, G., Tugwell, P., Robinson, V., et al. (2005). Transcutaneous electrical nerve stimulation for the treatment of chronic low back pain: a systematic review. Spine (Phila Pa 1976), 30(23), 2657-2666.

Khadilkar, A., Odebiyi, D. O., Brosseau, L., & Wells, G. A. (2008). Transcutaneous electrical nerve stimulation (TENS) versus placebo for chronic low-back pain. Cochrane Database Syst Rev(4), CD003008.

Langley, G.B., Sheppeard, H., Johnson, M. et al. (1994). The analgesic effects of transcutaneous electrical nerve stimulation and placebo in chronic  pain patients. A double blind non-crossover comparison. Rheumatol Int, 4, 119-123.

Long, D.M. & Hagfors, N. (1995). Electrical stimulation in the nervous system: the current status of electrical stimulation of the nervous system for relief of pain. Pain, 1, 109-123.

Melzack, R., & Wall, P. D. (1988). The Challenge of Pain (2nd ed. Vol. Rev). London, England

New York, USA: Penguin Books.

Nijs, J., Meeus, M., Oosterwijck, J. V., Roussel, N., Kooning, M. D., Ickmans, K., et al. (2011). Treatment of central sensitization in patients with 'unexplained' chronic pain: what options do we have? Expert Opin Pharmacother.

Porreca, F. (2011). Chronic Pain: It's More Than Peripheral Postgraduate Institute of Medicine.

Robinson, A.J. (1996). Transcutaneous electrical stimulation for the control of pain in musculoskeletal disorders. J Orthop Sports Phys Ther, 24, 208-226.

Rossini, M., Viapiana, O., Gatti, D., de Terlizzi, F., & Adami, S. (2010). Capacitively coupled electric field for pain relief in patients with vertebral fractures and chronic pain. Clin Orthop Relat Res, 468(3), 735-740.

Wall, P.D. (1994). Textbook of pain. Edinburgh: Churchill Livingstone.

Warke, K., Al-Smadi, J., Baxter, D., Walsh, D. M., & Lowe-Strong, A. S. (2006). Efficacy of transcutaneous electrical nerve stimulation (tens) for chronic low-back pain in a multiple sclerosis population: a randomized, placebo-controlled clinical trial. Clin J Pain, 22(9), 812-819.

Yokoyama, M., Sun, X., Oku, S., Taga, N., Sato, K., Mizobuchi, S., et al. (2004). Comparison of percutaneous electrical nerve stimulation with transcutaneous electrical nerve stimulation for long-term pain relief in patients with chronic low back pain. Anesth Analg, 98(6), 1552-1556, table of contents.

Blog 3: Electrical stimulation and the placebo effect on chronic pain

Although much of the literature reports that electrical stimulation treatment for chronic pain is not as successful as treatment for acute pain, we feel that there are some significant findings worth mentioning.

Cohen (1994) reported that almost 25% of 1000 chronic pain patients treated with TENS had their pain relieved to the point at which no other therapy was necessary.  Long and Hagfors (1995) found that 25-30% of 3000 patients surveyed across five different pain centres, who were previously incapacitated by pain, had significant pain relief with TENS alone. Robinson (1996) reviewed a number of studies in the use of TENS to control both acute and chronic pain related to musculoskeletal disorders.  From the review, it was concluded that although TENS is capable of producing clinically relevant pain relief, the pain relief is often of short duration and therefore only a small percentage of patients achieve lasting pain relief. 

In comparison, Beecher (1992) determined that an average of 35% of patients obtained satisfactory pain relief from placebo treatment, although some studies have reported 100% of patients respond positively to placebos (Wall, 1994).  The study by Wall was found to be a stand-alone case therefore we find the complete positive effect difficult to agree with, especially with the decent amount of conflicting literature. In support of this, Langley and colleagues (1994) noted that placebo studies may be inappropriate as the patient can distinguish active from inactive TENS – therefore making it highly unlikely that a placebo positive response rate could reach 100% as suggested by Wall.

However, we did come across a study in which the investigators used methods of ‘strong suggestion’ whilst administering placebo treatments to patients. This encouraged patient mentality to be influenced towards truly believing they were receiving TENS. In doing so, Deyo and colleagues may have in fact enhanced the placebo impact on pain which was found to be similar to the effects achieved from active TENS.  

Figure 3.0 Portable TENS machine readily available to the public

 http://static.medshop.com.au/images/D/17841_MES_Everyway_EV906_4_Channel_Digital_Tens_EMS_Machines.jpg 

In relation to our previous post, although a specific analgesic effect for TENS has not been conclusively proven in the treatment of chronic pain, the brief results mentioned speak for themselves.  The assessment of long-term pain relief with TENS on chronic pain is difficult as the studies are complicated to conduct and researchers use different criteria and guidelines to judge successful pain relief.  After considering the positive outcomes shown through the use of TENS along with the evidence for placebo effects, we are left wondering if there can be a combination of the two. Does receiving treatment with TENS cause clinical pain relief that is enhanced by a belief that it will work (therefore, the placebo effect)?  In our opinion, regardless of whether the mechanism of pain relief for chronic pain sufferers is analgesic- or placebo-based, these patients are still being offered a treatment modality which may provide much needed pain relief.  Successful patient management should incorporate a trial of TENS as part of an overall care plan that includes the control of pain.

Blog 2: Investigating the use of various modalities of electrical stimulation for chronic pain – how effective are they?

The general consensus appearing in the literature since the late 1960s, gives credence to the efficacy of various modalities of electrical stimulation (in particular TENS) for the treatment of both acute and chronic pain.  If you happen to be one of many sceptics who question the use of electrotherapy agents in general, we urge you to keep an open mind as we investigate the use of these agents as treatment modalities for chronic pain.

TENS - Transcutaneous electrical nerve stimulation

TENS has been used in the treatment of patients suffering fibromyalgia with modest treatment results even though it has been reported that widespread and poorly localised pain states are less likely to be reactive to TENS (Nijs, 2011). Originally described by Melzack et al (1988), the ‘gate control theory’ remains the preferred explanation for the mechanism of TENS. This theory states that TENS opens large-afferent nerve fibres, which transmit non-nociceptive signals, thereby decreasing transmission through the small afferent fibres that transmit pain. This effect was shown by Itoh (2009) to be persistant for a varied amount of time on cessation of therapy depending on the type of TENS applied.  Cheing & Hui-Chan (1999) reported that a placebo effect may account for up to 32% of treatment success in the use of TENS; however this treatment modality still proved more effective than massage and electroacupuncture for relieving chronic musculoskeletal pain. This was particularly true for high frequency TENS, which was shown to release endogenous opioids from the lumbar cerebrospinal fluid. Durmis (2010) found TENS resulted in an increase in muscle strength, decrease in joint stiffness and decrease in muscle spasm, all of which can contribute to an analgesic effect.

The two most common application modes of TENS include:

1. High frequency/conventional TENS = 40-150Hz, 50-100μs pulse width, low intensity
2. Low frequency/acupuncture-like TENS = 1-4Hz, 100-400μs pulse width, high intensity

Conventional TENS has been associated with a faster onset and shorter duration of analgesia compared to acupuncture-like TENS (Khadilkar, 2005).

3 other standard modes of TENS (Khadilkar, 2005):

1. Brief-intense = >80Hz, >150μs pulse width, comfortable-tolerable intensity
2. Burst mode = bursts <10Hz and comfortable intensity
3. Modulation = one or more stimulation parameters are randomly modulated

PENS - Percutaneous electrical nerve stimulation

PENS combines the advantages of TENS and electroacupuncture in which acupuncture needles are placed in non-acupuncture points. This reportedly leads to pain reduction of up to two hours as endogenous opiods, including  β-endorphin, are released due to the stimulation (Yokoyama, 2004).  Yokoyama (2004) does explain that this may have a ceiling effect in which the accumulation of anti-opioid substances within the CNS may account for the development of pain tolerance.  Numerous sources within the literature report that PENS is most effective when delivered at mixed frequencies as this modulation affects the pattern of neurotransmitter release within the CNS and reduces the accommodation effect (Ghoname, 1999 & Yokoyama, 2004):

• 2Hz - stimulate µ and δ opioid receptors
• 100Hz - activation k-opioid receptors in CNS
• Recommended duration = 30 minutes 

Figure 2.0: patient receives PENS acupuncture at Womack Army Medical Centre to address chronic pain he suffers after being wounded in improvised explosive device attacks in Iraq (http://paraglideonline.net/062509_life1.html)

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CCEF - Capacitively coupled electrical field stimulation

CCEF has been reported to potentially increase bone formation by up-regulating osteoblast function (Rossini, 2010). In the study by Rossini, postmenopausal women with multiple vertebral fractures and chronic pain who received CCEF treatment were found to decrease their intake of NSAIDS, however no other differences were noted in comparison to the control group.  No side effects were reported with this treatment, even with long duration of use.  Once again, it was suggested by the authors who conducted the study that a placebo effect may have come into play in decreased pain perception.

TCES – Percutaneous transcranial electrical stimulation

TCES activates opiate mechanisms in the brain's anti-nociceptive system, resulting in β-endorphin, serotonin and noradrenalin release (Gabis, 2009). Analgesia was found to be concentrated within the raphe (medial brainstem).  Gabis (2010) explained that 40% of patients receiving placebo TCES reported pain relief; this again suggests to us that the placebo effect is very powerful when treating chronic pain.  However, Gabis further reported decreased pain in the placebo group which was maintained at 3 months which suggests a vanishing placebo.

Please click HERE to watch an instructional video on how TCES is applied.

rTMS – Repetitive transcranial magnetic stimulation

rTMS stimulates the cerebral cortex over either the motor cortex or the dorsolateral prefrontal cortex, which produces analgesic effects up to three weeks post-treatment(Nijs, 2011). This safe, non-invasive technique for treating chronic pain is more effective in suppressing central pain as opposed to peripheral pain as it targets cerebral structures involved in pain processing (see Blog 1).  Unfortunately, there is limited equipment availability due to its bulk and expense, which creates a limitation in prescribing this technique as part of a patient’s pain management regime – only a few specialised centres have these available.

Please click HERE to watch a video outlining how rTMS works and how this is helping patients with depression.

Upon review of the various electrical stimulation techniques used in the management of chronic pain, we found that most of the evidence seems to point to a placebo effect coming into play rather than a specific analgesic effect of the modalities discussed. The research seems to aim to demonstrate that electrical stimulation (particularly TENS) is a superior treatment method in comparison to placebo effects.  This is something which we feel warrants further investigation and we will be discussing in our next blog.

Blog 1: Chronic and centralised pain: what is it and how does electrical stimulation affect it?

As physiotherapists we will come across and treat a variety of acute injuries and conditions. However, we will also be exposed to patients with persistent physical issues that present with chronic pain. Firstly, it is important to define and explain the concept of ‘chronic’ or ‘centralised’ pain.  Chronic pain has been defined as persistent pain lasting longer than 3 months and occurring on at least 50% of days (Khadilkar et al., 2005) or as pain that persists long after all possible healing has occurred (Cheing & Hui-Chan, 1999). 

Chronic pain can cause increased sensitivity to non-noxious stimuli (hyperalgesia) as well as noxious stimuli (allodynia) (Cheing & Hui-Chan, 1999).  It is also possible for chronic pain sufferers to develop an assortment of other presenting symptoms including muscle spasm, decreased strength and range of motion (ROM); all of which can hinder activities of daily living (ADL’s). These areas have been described as important, attainable treatment goals to aim to improve when treating patients with chronic pain (Khadilkar, et al., 2005).

The mechanisms behind chronic pain have been studied as neurological and termed ‘centralized sensitization’. Figure 1 from Medscape (Porreca, 2011) shows a summary of the many processes involved in the centralisation of pain.

 

Figure 1.0: Mechanisms of central sensitization (Porreca, 2011)

Figure 1 mainly illustrates what is termed the ‘bottom-up’ mechanisms of centralisation of pain (Nijs et al., 2011) as it relates to the signal caused by an external stimuli travelling up to the CNS. Nijs, et al., 2011 also found neural activity in pain areas of the brain are persistently higher in patients with centralized pain, which may explain increased sensitivity to acute pain (Cheing & Hui-Chan, 1999). Changes in brain activity have been shown to affect the descending modulation of pain by the CNS (Nijs, et al., 2011), which affects the facilitation of pain and eventually leads to temporal summation or wind up.

All the processes believed to be involved in central sensitization of pain (after all repair has occurred) relate to neurological mechanisms. Therefore it seems fitting that electrical stimulation will affect this process as it targets nerve processing which we will be divulging in our next blog.  We will be further investigating the many modalities of electrical stimulation and how this affects patients with chronic pain.