TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION
Our understanding of pain mechanisms and how pain is perceived has undergone significant changes. Initially, pain was viewed as an emotion rather than a sensation. It was said to be the opposite of pleasure. This theory dated back to the time of Aristotle. The traditional theory, described as the specificity theory by Descartes in 1664, conceived of a pain system as a direct channel from the skin to the brain (Melzack & Wall, 1982). This concept was supported and expanded on by Von Frey, who argued that there were specific pain receptors (Sinclair, 1953). As scientific experimentation grew towards the later part of the last century, Goldscheider developed the pattern theory, which stated that sensation was based on spatial and temporal patterns of a number of impulses (Nafe, 1929; Geldard, 1953). Zotterman (1936) discerned A-Delta and C afferent nerve fibers. Later research stated that A-delta fibers carried fast, but short-lived, well-defined pain impulses while C fibers carried slow, diffuse, long-duration pain.
The modern basis for the widespread use of transcutaneous electrical nerve stimulation (TENS) for pain control is the gate control theory proposed by Dr. Ronald Melzack and Dr. Patrick Wall (1965). This theory suggests that hypothetical "gates" in lamina V of the substantia gelatinosa could be "closed" to block pain stimuli traveling from A-delta and C fibers in the peripheral nervous system where they synapse into the central nervous system. Although this theory was later modified, it created much notoriety at the time and revolutionized the way most practitioners viewed and treated chronic pain.
In 1967, C. Norman Shealy, M.D., a neurosurgeon who had been implanting dorsal column stimulators (DCS), discovered that devices that transmitted electricity transcutaneously were just as effective without the risks associated with surgery (Shealy, Mortimer, & Reswich, 1967). With the Melzack-Wall theory behind him, Shealy's work renewed interest in electromedicine and resulted in the beginning of the modern day TENS devices.
Transcutaneous electrical nerve stimulation is an established modality with over 250,000 TENS units prescribed annually in the United States alone. Accordingly, much information is available on standard TENS applications, precautions, contraindications, side effects and results (Mannheimer & Lampe, 1984; Tapio & Hymes, 1987). Mixed results have occurred due to several factors, such as waveform, frequency, pulse repetition rate, intensity, alternating vs. direct current, electrode placement and treatment time. Perhaps the single largest variable is the education, or lack thereof, provided to health care practitioners recommending these devices and instructing patients in their use. Many professionals simply give the unit to a patient with the factory settings and never alter them, leaving each device as a hit or miss item. TENS devices must be tried at a variety of settings to achieve optimal pain relief for a given patient. In principle, TENS applies an electrical force that stimulates pain-suppressing A-beta afferent nerve fibers which compete against pain-carrying afferent nerve fibers. The same stimulation would occur if one lightly tapped the painful body part repeatedly with a pen, spoon, or other blunt object. Ice, massage, heat, manipulation and other long-standing therapy techniques have relieved pain this way for centuries.
Energy Source
Most TENS units work with currents in the milliampere range delivered for about 250 microseconds. The most common output is biphasic to avoid the side effects of polarization. They are powered either by alkaline or nickel cadmium batteries. In general, alkaline batteries are preferred for constant stimulation because they have a relatively slow, linear power decay. Rechargeable batteries have a series of peaks or near-peaks in their discharge rate because each cell discharges in series. Accordingly, rechargeable batteries should be avoided, especially in the cheaply made Taiwanese devices.
Electrodes
Initially, dry pads were provided that required the use of a gel. This was messy, provided uneven conductivity and caused minor skin burns at a high current. At present, self-adhesive electrodes are available that are semi-disposable and generally affordable. In this day and age of concern over deadly infectious diseases, it has become common practice for clinicians to keep a separate set of electrodes for the exclusive use of each patient.
Pulse Repetition Rate (PRR)
The reader will often see this listed as "frequency" on a typical TENS unit. According to the previous discussion in this chapter, the lower the PRR setting, the greater number of frequencies the patient will be exposed to; hence, the greater potential for pain relief. For the average pain patient, we recommend setting the PRR to the lowest setting for initial trials. Pomerantz (1981) has also shown by naloxone blocking studies that endorphins are only released at PRR settings of 8 Hertz or less.
Pulse Width
Wider pulses spread the current over greater distances. The maximum parameters in most TENS units ranges from 50 to 400 microseconds. The further apart the electrodes are, the wider the pulse width should be.
Electrode Placement
Electrode placement is perhaps the greatest variable in eliciting successful results with TENS. Electrodes can be placed "between the pain and the brain," along nerve roots, dermatomes of the respective nerve levels, following the referred pain pathway, or on trigger points. Janet Travell, M.D. started researching trigger points in 1957 (Travell & Simons, 1983). Trigger points are named such because they trigger pain when pressed. They are areas of localized tenderness that usually form with a persistent muscle spasm. For the purpose of this discussion, they can be measured as having higher conductivity than normal tissue. In most cases, electrical treatment directly on the point is indicated. Sometimes, this will increase the pain (as explained by the pattern theory of pain). If this occurs, treating across the area with microcurrent stimulation at 0.5 Hz will almost always alleviate it.
With the parameters discussed, it is apparent that several combinations of PRR, pulse width, intensity, electrode placement, time and frequency of stimulation may have to be attempted before desirable results are obtained. Perhaps this is the reason why most major medical insurance companies prefer to rent a TENS device to a patient for the first month before approving it for purchase.
Indications
Several studies have documented the desirable effects of TENS. Loeser and his coworkers (1975) examined TENS-induced relief of pain for headaches, cervical arthritis, low back, phantom limb, arthritis and acute post-operative pain. Tapio and Hymes (1987) reviewed the efficacy of TENS on low-back pain, cancer pain, post-herpetic neuralgia, phantom limb pain, rheumatoid arthritis, angina pectoris, various acute conditions, dysmenorrhea, visceral pain and several other disorders. Andersson (1976) found TENS could raise the threshold for dental pain. By using low-frequency, high-intensity stimulation (the so-called "acupuncture-like TENS") he was able to increase his success rate in pain reduction from 40 to 60%.
Contraindications
There are very few contraindications with TENS. All electrical modalities are contraindicated for pregnant women and patients with demand-type pacemakers. In general it is advisable that patients not drive or operate heavy machinery while TENS is being applied. Also, it is essential that electrodes from milliampere TENS units are not placed on the head or neck. This is especially true regarding the carotid sinuses as stimulation of the baroreceptors may result in a vaso-vagal syncopé.
TENS Summary
TENS is now a widely used modality for the treatment of general acute and chronic pain syndromes. When effective, the ease of use, general safety and portability make it a treatment over the long term use of medications and nerve blocks for chronic pain. Modern drug practitioners would do well to recall Aesculapius' motto regarding healing; primo non nocere (first, do no harm).
A disadvantage is the tinkering required for the average pain patient to find the best combination of variables for effective relief. Even after repeated attempts at different parameter combinations, TENS devices may not alter pain results. Although effective to some extent, they are simply an application of force, a counter-irritant produced analgesia. They provide no significant residual effect and as with drugs, tolerance is a significant problem.
MICROCURRENT ELECTRICAL THERAPY
Becker and Nordenström have provided a rational basis for a new and vastly more effective form of electromedical intervention for which Joseph M. Mercola, D.O. and Daniel L. Kirsch, Ph.D. (1994) coined the term "microcurrent electrical therapy" (MET). A growing body of research shows the effectiveness of MET to accelerate, and even induce healing. Eaglstein and Mertz (1978) have shown moist wounds to resurface up to 40% faster than air-exposed wounds. Falanga (1988) found that certain type of occlusive dressings, like Duoderm, accelerate the healing of wounds. It is probable that these dressings achieve their effects by promoting a moist environment (Kulig, Jarski, & Drewek, 1991). When a wound is dry, its current flow is shut off. The moisture may allow the endogenously produced current of injury to flow and promote wound healing. Electrical stimulation of the wound also tends to increase the amount of growth factor receptors which increases the amount of collagen formation (Falanga, 1987). Electricity was first used to treat surface wounds over 300 years ago with charged gold leaf to prevent smallpox scars (Robinson, 1925). There are several recent studies supporting the beneficial effects of treating wounds with an artificial current of injury (Goldin, 1981; Jeran, 1987; Ieran, 1990; Mulder, 1991). Experimental animal wound models in the 1960's demonstrated that electrical intervention can result in accelerated healing with skin wounds resurfacing faster, and with stronger scar tissue formation (Carey & Lepley, 1962; Assimacopoulos, 1968). Assimacopoulos (1968) published the first human study using direct electrical current for healing. He documented complete healing of chronic venous stasis leg ulcers in three patients with six weeks of electrical therapy. One year later the most frequently cited work in the history of electrical wound healing was published by Wolcott and Wheeler (1969). They used direct currents of 200-1,000 microamperes for 67 patients. Gault and Gatesn (1976) repeated the Wolcott and Wheeler protocol for 76 additional patients with 106 ischemic skin ulcers. Carey and Wainapel (1985) performed one of the only studies on this subject published with equal and randomized control and study groups. All of these studies documented significant accelerated healing with electrical stimulation. Working with Wolcott and others, Rowley et al. (1974) updated their initial experience with another group of patients having 250 ischemic ulcers of various types. These included 14 symmetrical control ulcers. The stimulated ulcers had a fourfold acceleration in healing response compared to the controls. One additional consistent observation in these studies was that there was a reversal of contamination in the wounds. Wounds that were initially contaminated with Pseudomonas and/or Proteus were usually sterile after several days of MET. Other investigators have also noticed similar improvements and encourage the use of this therapy as the preferred treatment for indolent ulcers (Kaada, Flatheim, & Woie, 1991; Barron, Jacobson, 1985; Lundeberg, Eriksson, & Malm, 1992; Alvarez et al., 1983). Additionally, no significant adverse effects resulting from electrotherapy have been documented (Weiss, 1990). A review of the literature by Dayton and Palladino (1989) shows that microcurrent electrical therapy is clearly an effective and safe supplement to the non-surgical management of recalcitrant leg ulcers.
Some of these studies used unipolar currents that were alternated between negative and positive based on various criteria. Some researchers initially used negative current to inhibit bacterial growth and then switched to positive current to promote healing. To date no study has compared this variable of MET. However, there is some compelling basic science research, and one animal study suggesting that a bipolar current, which provides both negative and positive phases, may be better for wound healing (Stromberg, 1988; Windsor, Lester, & Herring, 1993).
As mentioned previously, in the 1960s Dr. Becker demonstrated that an electrical current is the trigger that stimulates healing, growth and regeneration in all living organisms. He found that repair occurs after an injury in response to signals that come from an electrical control system and suggested that this system became less efficient with time. Dr. Becker (1985) developed his theory of biological control systems based on concepts derived from physics, electronics, and biology. He postulated that the first living organisms must have been capable of self-repair, otherwise they never would have survived. The self-repair process requires a closed-loop system. A specific signal is generated which causes another signal to start repair. The injury signal gradually decreases over time with the repair process until it finally stops when the repair is complete. Such a primitive system does not require demonstrable consciousness or intelligence. Therefore, many animals actually have a greater capacity for self-healing than do humans. Science has amassed a vast amount of information on how the brain and nervous system work. Most of this research involves the action potential as the sole mechanism of the nerve impulse. This is a very sophisticated and complex system for the transfer of information. It is helpful to compare this currently accepted process of the nervous system to a computer. The fundamental signal in both the computer and the nervous system is a digital one. Both systems transfer information represented by the number of pulses per unit of time. Information is also coded according to where the pulses go and whether or not there are more than one channel of pulses feeding into an area. All our senses (e.g., smell, taste, hearing, sight and touch) are based on this type of pulse system. Like a computer, the nervous system operates remarkably fast and can transfer large amounts of information as digital "on and off" data. It is unlikely that the first living organisms had such a sophisticated system. Becker believes they must have had a much simpler mechanism for communicating information because they did not need to transmit large amounts of sophisticated data. Accordingly, they probably used a much simpler analog system. An analog system works by means of simple DC currents. Information in an analog system is represented by the strength of the current, its direction of flow, and slow wavelength variations in its strength. This is a much slower system when compared to the digital model. However, the analog system is extremely precise and works well for its intended purpose. Becker theorizes that the first living organisms used this analog type of data-transmission and control system for injury repair. He postulates that we still have this primitive nervous system in the perineural cells of the central nervous system. These cells comprise 90% of the nervous system. The perineural cells have semiconductor properties that allow them to produce and transmit non-propagating DC signals. This analog system senses injury and controls repair. It controls the activity of cells by producing specific DC electrical environments in their vicinity. It also appears to be the primary primitive system in the brain, controlling the actions of the neurons in their generation and receipt of nerve impulses. This allows it to regulate our consciousness and decision-making processes. Given this understanding, the application of the correct form of electrical intervention is a powerful tool for treating pain, initiating the endogenous mechanisms of self-repair, and altering states of consciousness.
Clinical Applications
Clinically, we can use a point finder (ohmmeter) to measure pathological tissue because it exhibits a reduction in conductivity. This seems to be true in every case except in inflammatory conditions where the hot fluids conduct extracellularly causing a false-positive readings. The less conductive tissue sets up an electrical difference, or potential, on either side of the injury that controls pain and signals the healing process. This is known as the current of injury (COI). Since some tissues conduct electricity better than others, it is possible to calibrate a measurement device to an area near the injury before treating. Once a low conductive area is found, a microampere current with an effective waveform can augment the current of injury to effectively control pain as well as initiate or increase the rate of healing. Lerner and Kirsch (1981) developed this system and called it bioconductive therapy. The same meter can read a post treatment response (PTR) measurement. Generally up to four, six to ten second applications of stimulation with two small diameter probes is adequate per electrode placement. Several varying placements in an area may be needed to obtain an improved PTR. Once the area is adequately treated the PTR will exhibit a higher value with a slower decay time (Ullis, 1983). When using an effective device the improved PTR will almost always be associated with the patient's subjective feeling of improvement.The devices used for bioconductive therapy have come to be known as microcurrent stimulators. They deliver a much weaker signal about 2,500 times longer per pulse than TENS. The full spectrum ("shotgun") of frequencies within each pulse at this wavelength provide a phenomenally effective therapy. It is believed that cells within a specific organ or tissue system communicate through specific frequencies in the microampere range. The right frequency activates the COI causing the system to tend towards homeostasis. Caution is advised against purchasing devices claiming to be "cybernetic", or able to measure and automatically deliver the correct frequency for a given patient. Although at least one manufacturer makes such a claim, there is no such technology or scientific support material to design such a thing at this time. Originally, bioconductive therapy devices were large, expensive, metered units designed for clinical use only. A good microcurrent device requires more than ten times the circuitry of a standard TENS. However, in 1982, what is now Electromedical Products International, Inc. (EPII) of Mineral Wells, Texas introduced the first homecare microcurrent stimulator to the market. Their product, called the Alpha-Stim 350 weighed six pounds and was about half the size of a shoe box. Using surface mount technology manufactured by robotics EPII has been able to manufacture scaled down versions since 1990 at a cost competitive with TENS. Since then a number of imitations have flooded the market, primarily from Taiwan. Most of these products do not produce reproducible results because the design engineers know nothing about the underlying electrophysiology and they use cheap parts with tolerances as high as 35%. Alpha-Stim technology is actually produced by using two waveforms for each channel to create a full bioelectrical frequency range and introduce random factors into the waveform preventing the nervous system from recognizing it, and therefore habituating to it. The biggest mistake practitioners make with microcurrent devices is to use them the same way they would use a TENS device. As an example, TENS is often applied on either side of and close to the spine for back pain. This will not work with microcurrent technology because the current, following the path of least resistance, is too weak to actually reach the spine.
Step One: History and Brief Exam
It is extremely important to take a comprehensive history before beginning MET. One should determine when the pain first presented, its frequency, duration, intensity, limitations-of-motion, positions which exacerbate the pain and any precipitating factors. Ask about the specifics of previous treatments. Microcurrent electrical therapy is a holistic procedure. It may be necessary to clear the body of any and all electrical "blocks" in order to achieve the best results (more on this later).
Immediately before each treatment determine the patient's current pain level and the positions that exacerbate the pain. Ask the patient to rate their present pain on a scale of 0 (no pain) to 10, with 10 being excruciating, debilitating pain. Tell the patient to consider 10 as "the worst this condition has been". Also note any immediate limitations-of-motion, positive orthopedic and neurologic test findings, and psychological distress. This therapy usually produces instantaneous results so these indicators are necessary reference parameters to determine effectiveness throughout a single treatment session.
Adjust the Settings
Use a low frequency, preferably 0.5 Hz most of the time. It is unusual to ever need to use other frequency settings. However, if 0.5 Hz doesn't work, and everything else described herein has been tried, use a higher setting. In MET, this usually means 80 to 100 Hz. These higher frequencies are sometimes best for the first few minutes of treatment for inflammatory articular problems. Set the current intensity level at the highest comfortable position which is usually 500 to 600 microamperes (A) for probes, although it is sometimes slightly less for the silver-silver/chloride (Ag-AgCl) electrodes. Do not use any other type of self-adhesive electrodes for MET. Probes must be applied using a firm pressure, but less than the amount of pressure that would cause pain.
Treatment Strategy
There are several principles one must remember when treating patients with MET. The patient should be in a relaxed position to receive maximum beneficial effects. The most important variable is the position of the probes, or pads. Position them in such a way that if a line was drawn between them that line would transect the problem area. Keep in mind that the body is three dimensional. Therefore, there will be many possible ways to draw a line through the problem. Some lines will work much better than others! Sometimes it is helpful to imagine the problem area of the body as being transparent. As mentioned above, do not place the electrodes on each side of the spine for back pain as is done with TENS. With this placement the current will travel just under the skin and never reach the problem. A better way is to place one electrode next to the spine and the other on the contralateral side, anteriolaterally (front and opposite side). A line drawn between those will go right through the spinal nerves. Treat head, neck, and back (axial skeleton) problems bilaterally. If the other side is ignored, there is a good chance the problem will have been missed because pain often exhibits on the tense side which may just be compensating for muscular weakness on the other side. So after a few 10 second approaches with small diameter probes, or about 10 minutes with self-adhesive electrode pads, reverse sides.
Quick Probe Treatments
When using probes treat for 10 seconds per site. First treat in an "X" manner over an area wider than the problem. An example of this would be to treat the whole back for back pain. This can be done by placing one probe on the right shoulder and the other on the left hip, and then one on the left shoulder connected to the right hip. One treatment "set" is about five or six of these ten second stimulations, each at a different angle of approach (e.g., two obliques, two medial-lateral, and two anterior-posterior, etc.). Often the pain will migrate as a response to therapy. Follow it. Use the same treatment strategy described above for the pain's new location.
When to Stop
Reevaluate the patient after a few treatment sets. For some simple problems, it is preferable to reevaluate after each set. Use the original criteria. It is not enough to ask if the patient feels better, ask for a specific percentage of how much better. Also reexamine for objective signs like range-of-motion increases, etc. Stop when the pain is completely gone or when the improvement has reached a plateau after several sets of treatment. Continuing to treat the area at this time may cause the pain to return! If the pain is gone stop treatment for that day even if the patient only had one minute of treatment. If the patient can no longer identify any pain, but complains of stiffness, this is also a good indication that it is time to stop. Although most people will achieve immediate results, some will have a delayed effect and others will have a combined effect, continuing to improve over a day or two after the treatment.
Follow-up
The average patient should be given at least three treatments to evaluate their response to microcurrent electrical therapy. It helps to explain to the patient that the effects are cumulative. Like antibiotics, one must take several doses over a period of time to get results. Although results will often be seen during or subsequent to the first treatment, the longevity of the results can only be evaluated over the course of a few treatments. In some cases the results will plateau to a similar time period regardless of treatment. For example, a patient may only get two days of relief no matter what combination of treatment strategies are employed. For these and in cases of severe pathology, the effectiveness may only be short-lived so a MET device should be prescribed for home care. After an initial series of up to ten treatments, a good rule of thumb is to prescribe a unit to anyone with a chronic condition who requires more than one palliative treatment per month, and to those who have progressive pathologies.
Tips for Limited or Poor Results
Microcurrent electrical therapy will not work for everybody. However, as originally reported in an earlier version of this text, in nearly all cases of failure the common denominator is that the patient has had a significant exposure to a strong electrical current. This means that they have either been held by electrical current at some time in their life, or that they have been treated with milliampere TENS or similar modalities for a prolonged period of time (e.g., years). As yet, there is still no known effective method for treating people so afflicted.
The most commonly seen reversible reason patients fail to respond to treatment is that they have surgical or traumatic scars. Identify all scars by taking a very thorough, persistent history, and examining the patient completely. All scars are important no matter how old or how far they are from the chief complaint. Scar tissue impedes the systemic flow of endogenous bioelectricity because it is a poor conductor of electricity. Accordingly, scar tissue may interfere with the patient's entire bioelectrical system. If scars are present they should be treated with silver/silver-chloride (Ag/AgCl) electrodes for ten minutes per scar, at least four times. Simply cover the scars with the electrodes or, for large scars, place the electrodes on the ends of the scars. This may be done four days in a row or there can be a short interval of up to a few days between the scar treatments. When treating scars the person may experience a significant surge of energy. It can be viewed as if an electrical bioresistor is broken down. Patients will often report feeling half their age, or 20 years younger after scar therapy. Since people have nothing to compare their life experience with, they usually attribute the subtle effects of scars on their electrical system as normal aging. Be aware that this treatment will more often than not also increase the pain because the whole body and mind "wakes up", including the painful part. However, when this happens in nearly all cases, the painful area can then be successfully treated. Always schedule enough time to treat the pain after the scar treatment so the patient will not need to endure even a temporary increase in pain. If all the scars are treated and there is still no or poor results there are a few other options. Question the patient about old injuries that may not have healed properly. These could also be electrical blocks and should be approached in the same way as scars. To relieve pain in some patients a lower current setting of no more than 100 A with the Ag/AgCl electrodes for one or more hours at a time is necessary. Higher pulse repetition rates may produce results in some people when the 0.5 Hz fails, but this is rare.
CRANIAL ELECTROTHERAPY STIMULATION
Cranial electrotherapy stimulation (CES) is the application of low-level pulsed electrical currents (usually less than one milliampere) applied to the head for medical and/or psychological purposes. Cranial electrotherapy stimulation has also been known by many other names. Transcranial electrotherapy (TCET), neuroelectric therapy (NET), alphasleep, electroanalgesia, electronarcosis and the original electrosleep are just a few of the more common terms that have referred to the same therapy. Cranial electrotherapy stimulation was first called electrosleep because it was thought to induce sleep. Rabinovich, a Russian, is given credit for making the first claim for electrical treatment of insomnia in 1914 (Achte, Kauko, & Seppala, 1968). In 1957, in the U.S.S.R., Anan'ev et al. published the first work on CES and the first book, simply titled Electrosleep, was published a year later by Gilyarovski. This generated a high degree of interest in the then-known Eastern Block countries and CES was soon adopted as a treatment modality. Obrosow (1959) reviewed the CES literature and published the first American paper on CES. By 1966 the first International Symposium on Electrotherapeutic Sleep and Electroanesthesia was held in Austria. Cranial electrotherapy stimulation use had spread worldwide by the late 1960's when animal studies of CES began in the U.S. at the University of Tennessee, and at what is now the University of Wisconsin Medical School. These were soon followed by human clinical trials at the University of Texas Medical School in San Antonio, the University of Mississippi Student Counseling Center and the University of Wisconsin Medical School. There are well over 100 published reports on CES in the U.S. and several times that amount in the European literature. The most comprehensive research review published to date on CES is a chapter in a textbook by Ray B. Smith, Ph.D. (1985). Dr. Smith has been researching CES since 1972. He concluded, "There are 40 studies of CES readily available in the U.S., in which the dependent variable is reliable. When these are examined alone it becomes apparent that CES is effective in alleviating symptoms of anxiety, depression, and insomnia...CES appears effective as a treatment for withdrawal in the chemically dependent person...Other promising areas of treatment are in hypergastric acidity and migraine headaches." Dr. Smith adds, "CES appears to be safe, with no harm or negative side effects having been reported to date in controlled studies...Finally, while one usually assumes some placebo effect from a treatment as dramatic as this, none has been reported in studies controlled for this effect." Sidney Klawansky, M.D., Ph.D. (1993) has recently concluded a meta-analysis of CES at Harvard and has also found it to be efficacious. Open marketing of CES devices began in the 1970's in the U.S. for the treatment of anxiety, depression and insomnia. To date, several thousand Americans are treated with CES annually, and more than 50,000 people own CES devices which have been prescribed for home use. From a broad reading of the published literature, no negative effects or contraindications have been found from the use of CES, either in the U.S. or in other parts of the world. Regardless of these facts, CES is in jeapordy of being removed from the market in the United States due to a recent FDA action.