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Electroanalgesia is a method of pain management that involves the introduction of a weak electric current at the site of pain .


The purpose of electroanalgesia is to reduce or eliminate pain.


There are few contraindications for the use of electroanalgesia. It should not be used with pregnant women or patients with pacemakers , heart problems, hearing aids or hearing-aid implants. The low-level current can often interfere with the working of pacemakers and hearing aids.


Electroanalgesia is a relatively new treatment method (since the late 1960s) to mitigate or eliminate pain. The concept, however, dates to the time of Aristotle, when patients who were experiencing pain were urged to stand in shallow water on top of electric fish (probably rays). It was not until 1965 when Dr. Ronald Melzack and Dr. Patrick Wall suggested the gate control theory that a legitimate scientific basis for electroanalgesia was found. This theory, and the endorphin release theory, became the foundational rationale of electroanalgesia.

The gate control theory is the most widely held explanation for why electroanalgesia works. It says that by stimulating nerve sensors in the skin through electricity, a gate is closed in a part of the spinal cord , preventing pain messages from being carried to the brain . The patient has no perception of pain, although the message of pain at its site of origin still exists.

The endorphin release theory, in contrast, says that electricity stimulates the production of endorphins and enkaphalins—natural, morphine-like protein peptides— in the brain. These peptides block pain messages like conventional medications do but without the side effects associated with introducing pain control with opioids, for instance. Electroanalgesia cannot create a physical dependency like pain medications can.

Electroanalgesia may be used to relieve pain found in migraine and tension headaches, lower back, phantom limb syndrome, various forms of arthritis, cancer , angina pectoris, dysmenorrhea, posthepatic neuralgia, diabetic neuropathy, bursitis , sports injury, wounds , and after surgery. It can also be used to mitigate dental pain.

There are two forms of electroanalgesia: transcutaneous electrical nerve stimulation (TENS) and percutaneous electrical nerve stimulation (PENS). Electrical dental analgesia (EDA) is a form of TENS therapy and has been approved by the FDA since 1996.

TENS therapy uses one-inch (2.5 cm) diameter conductor electrode pads with adhesive backings. These electrode pads are placed on the skin near the site of the pain. The locus of the pain is the only reference for placement of these electrode pads. Studies have shown that endorphins are only released at pulse repetition rates (PPR)—or frequencies—of 8 Hz or less. Wider pulses spread the current over a greater area; most TENS units emit pulse widths ranging from 50–400 microseconds. Each TENS treatment will consist of the determined frequency (number of Hz) delivered for a certain length of time (perhaps one or two hours a day and sometimes more often at night) for a specified period of time (seven days; 14 days; 24 days). In low-frequency high-intensity stimulation, "quick probe treatments" may be delivered for 10 seconds each time; however, one "treatment" consists of several sets of five or six of these 10-second stimulations, and several "treatments" may be given consecutively. High-frequency TENS has been shown to suppress spontaneous and abnormal activity in a damaged nerve, and frequencies of 80 Hz or higher may be the treatment of choice in certain circumstances.

PENS therapy is a combination of acupuncture and electroanalgesia. In PENS treatment, fine stainless steel

acupuncture probes (rather than electrode pads) are attached to bipolar leads coming from an electrical generator. These probes are inserted into the soft tissue like acupuncture needles and the electricity running through them stimulates the pain sensors within and just beneath the skin. As with TENS, the level and length of stimulation, number of treatments, and number of treatment days, is determined. (In one study an alternating frequency of 15 Hz and 30 Hz was administered for 30 minutes three times a week.) Also as in TENS, the probes are inserted at or near the locus of pain rather than at traditional acupuncture points. Because a patient's skin is punctured, universal sterile procedures must be used.

A similar therapy to PENS is electroacupuncture. In this treatment method probes carrying the electric current are inserted at traditional acupuncture sites rather than at the pain locus.


Dysmenorrhea —Painful menstruation.

EDA —Electrical dental analgesia.

Endorphins —Natural, morphine-like substances in the brain.

Enkaphalins —Natural, morphine-like substances in the brain.

PENS —Percutaneous electrical nerve stimulation.

TENS —Transcutaneous electrical nerve stimulation.

EDA is administered through small pads placed inside the mouth or on the outside of the cheeks. The patient controls the amount of electroanalgesic administered and feels only a pins-and-needles sensation rather than pain. Once the dental procedure is over and the EDA pads are removed, the patient has no residual numbing as often occurs with the use of local anesthetics.

Neither PENS nor electroacupuncture were approved by the FDA by 2001, and often are not covered by standard medical insurance. TENS and EDA have been approved. However, all of these electroanalgesic therapies should be used as a supplement to conventional treatment and should not be the primary or alternate course of treatment. Since pain is an indication of many serious conditions, pain should not be ignored or eliminated until the source of the disorder is found. Then, any number of pain management therapies including electroanalgesia may be used.


There is no preparation for this procedure, except to identify the location of the pain. For TENS treatment, the patient should be given three separate treatments in the practitioner's office. An assessment of the patient's pain level after treatment, measured against a standard scale, must be discussed and recorded. The patient can then be instructed in the use of the apparatus for self-treatment at home. Once several treatments are completed, the patient should be evaluated. If the pain has stopped or reached a plateau, treatment should cease. If the pain is gone, even after only one minute of treatment during the first treatment, treatment should cease for that day. Often the patient feels immediate relief; sometimes, it is delayed over a day or two. It is important to remember that with progressive pathologies such as cancer and degenerative diseases like arthritis, pain most likely will return. The patient will need repeated treatments which are often taken at home under the patient's control.

For PENS therapy, the patient receives treatment in the practitioner's office. The practitioner must locate the areas of pain and place the steel probes into the soft tissue at specific points near the pain.


With proper use, there is no need for aftercare from these procedures.


The only complications with electroanalgesic therapies are the risk of infection in invasive techniques (probes) and continuation of therapy after pain is eliminated or has reached it's lowest threshold. In these instances, continuing treatment may cause the pain to return.


Before treatments begin, the physician and patient must come to an agreement on the goals of therapy. Normal expected results are to diminish or eliminate pain; however, goals must be reasonable and workable according to the patient's condition. Often, patients report more freedom of movement, better sleep patterns, and considerable reduction in the need to use oral analgesics following electroanalgesic therapies.

Health care team roles

PENS therapists require special training in the use of the equipment and insertion of probes. There is an art to the therapy, much like the art associated with acupuncture.

TENS training is less delicate but still necessary. Since this therapy is relatively new, many physicians have written a prescription for a TENS unit, or given a unit to a patient without proper patient education about the use of the unit and the necessity for determining the appropriate frequency to obtain the necessary results. By administering the first three treatments in the office, the practitioner can determine the appropriate settings for the patient and his or her particular type of pain before sending the unit home with the patient.

Because dental patients control the amount of electronic anesthesia they receive, dentists and dental assistants must be trained in the use of the EDA units so they can instruct the patient how to dispense their individual level of pain suppression.



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Janie F. Franz