Surface neuromuscular electrical stimulation uses devices that transmit electrical impulses by way of electrodes placed on the skin. Although the various types of stimulation may differ in waveform or method of delivering current, electrical stimulation is postulated to generally have any of the following physiological effects:
- Re-education of muscle;
- Development and increase of muscle tone and strength;
- Maintenance or increase of range of motion;
- Improvement of local blood circulation;
- Prevention of muscle atrophy;
- Relaxation of muscular spasms;
- Create a state of generalized relaxation for relief of anxiety, depression, and/or insomnia.
The following are descriptions and uses of different types of surface electrical stimulation.
Transcutaneous Electrical Nerve Stimulation (TENS)
Transcutaneous electrical nerve stimulation (TENS) uses an electronic device that applies electrical stimulation to the surface of the skin at the site of pain, and is usually used to relieve chronic intractable pain, post-surgical pain, and pain associated with post-trauma injury. TENS has also been used to treat dementia by altering neurotransmitter activity and increasing brain activity, which is thought to reduce neural degeneration and stimulate regenerative processes. TENS consists of an electrical pulse generator, usually battery operated, connected by wire to two or more electrodes, which are applied to the skin.
Since 1977, a large number of devices have received marketing clearance through the U.S. Food and Drug Administration (FDA) 510(k) process. Marketing clearance via the 510(k) process does not require data regarding clinical efficacy; these devices are considered substantially equivalent to predicate devices marketed in interstate commerce prior to May 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified and do not require approval of a premarket approval application (PMA).
Transcutaneous Electrical Modulation Pain Reprocessing (TEMPR)
TEMPR is delivered in the same way as TENS, but instead of blocking pain signals, this therapy sends a “no pain” signal. Competitive Technologies, Inc. manufactures a device called CALMARE® Pain Therapy Treatment, which has received 510(k) marketing clearance from the FDA as a multi-channel TENS device. The company describes the Calmare Pain Therapy Treatment as “a non-invasive method for rapid treatment of high-intensity oncologic, neuropathic, and drug-resistant pain through a biophysical rather than a biochemical manner. The method incorporates electromedical equipment for electronic nerve stimulation, and uses the nerve fiber as a passive means to convey a message of normality to the central nervous system (CNS) by a procedure defined as scrambling or tricking of information, which then enables the CNS to modify the reflex adaptive responses.” The supposed advantage is that this is a multiprocessor apparatus able to simultaneously treat multiple pain areas in the individual. The patient experiences longer "no pain" periods after each successive treatment. TEMPR is administered in the doctor’s office under direct supervision of the physician, who provides an initial consultation to discern the most effective path for electrode placement. Treatment applications are interactive between the patient and the provider, with the provider attending and making adjustments approximately every 10 minutes throughout the treatment session, which typically lasts an hour.
Interferential (IF) Stimulation
Interferential stimulation (IF) uses paired electrodes of two independent circuits carrying medium-frequency alternating currents that work together to effectively stimulate large muscle fibers. The electrodes are aligned on the skin so that the current flowing between each pair intersects at the underlying target. IF therapy delivers higher currents than TENS, using two, four, or six electrodes, arranged in either the same plane for use on regions such as the back, or in different planes in complex regions such as the shoulder. This stimulation method has been investigated as a technique to reduce pain, improve range of motion, and/or promote local healing following various tissue injuries; uses include pre- and post-orthopedic surgery, joint injury syndrome, cumulative trauma disorders, increasing circulation, and pain management. There are no standardized protocols for the use of IF therapy; the therapy may vary according to the frequency of stimulation, the pulse duration, treatment time, and electrode-placement technique. A number of interferential stimulator devices have received 510(k) marketing from the FDA; examples include the RS-4i™ Interferential (RS Medical) and Medstar™ 100 (MedNet Services).
Microcurrent stimulation is similar to TENS, except that it uses current in the microampere range, which is 1000 times less than that of TENS and below sensation threshold. While TENS is used for pain, the sub-sensory microcurrent stimulation acts on the body’s naturally occurring electrical impulses to decrease pain and facilitate healing. The device is used to manage acute and chronic pain, reduce edema and inflammation, promote wound healing, and treat anxiety disorders. Examples include Health Pax™, VST Myo Dynamic Device™, and Electro-Acuscope™, among others.
A high-voltage pulsed galvanic stimulator generates small twin pulses of electrical current at an adjustable rate from two pairs (two pulses) per second to 100 pairs per second. Each pulse is much shorter in duration and has higher voltage than a conventional stimulator. The positive electrode behaves like ice, causing reduced circulation to the area under the pad and reduction in swelling. The negative electrode behaves like heat, causing increased circulation, reportedly speeding healing. Galvanic stimulation is used to treat pain and reduce edema.
H-wave stimulation differs from TENS in terms of its wave form; this is a unique form of electrical stimulation that uses a bi-polar and exponentially decaying wave form resulting in a pulse width measured in milliseconds rather than microseconds. H-wave stimulation is said to accomplish reduction of edema and the reduction or elimination of pain, as well as assist wound healing. H-wave electrical stimulation must be distinguished from the H-waves that are a component of electromyography.
In 1992, the H-Wave® muscle stimulator (Electronic Waveform Lab, Huntington Beach, CA) was cleared for marketing by the FDA through the 510(k) process. The FDA classified H-wave stimulation devices as “powered muscle stimulators.” As a class, the FDA describes these devices as being “intended for medical purposes that repeatedly contracts muscles by passing electrical currents through electrodes contacting the affected body area.” According to the FDA, manufacturers may make the following claims regarding the effect of the device: “1) relaxation of muscle spasms; 2) prevention or retardation of disuse atrophy; 3) increasing local blood circulation; 4) muscle re-education; 5) immediate post-surgical stimulation of calf muscles to prevent venous thrombosis; and, 6) maintaining or increasing range of motion.” Uses of the device not cleared by the FDA include, but are not limited to, treatment of diabetic neuropathy and wound healing.
Threshold electrical stimulation delivers low-intensity electrical stimulation to target spastic muscles during sleep. The stimulation is not intended to cause muscle contraction. Although the mechanism of action is not understood, it is thought that low-intensity stimulation may increase muscle strength and joint mobility, leading to improved voluntary motor function. The technique has been used most extensively in children with spastic diplegia related to cerebral palsy, as well as other motor disorders, such as spina bifida.
Devices used for threshold electrical stimulation are classified as “powered muscle stimulators.” As a class, the FDA describes these devices as “an electronically powered device intended for medical purposes that repeatedly contracts muscles by passing electrical currents through electrodes contacting the affected body area.”
Sympathetic therapy describes a type of electrical stimulation of the peripheral nerves that is designed to stimulate the sympathetic nervous system in an effort to "normalize" the autonomic nervous system and alleviate chronic pain. Unlike TENS or IF electrical stimulation, sympathetic therapy is not designed to treat local pain, but is designed to induce a systemic effect on sympathetically induced pain.
Sympathetic therapy uses four intersecting channels of various frequencies with bilateral electrode placement in various locations on the feet, legs, arms, and hands, depending on the location of the patient's pain and the treatment protocols supplied by the manufacturer. Electrical current is then induced with beat frequencies between 0 and 1000 Hz. Treatment may include daily one-hour treatments in the physician's office, followed by home treatments if the initial treatment is effective.
The Dynatron® STS device and a companion home device, Dynatron STS® Rx, are devices that deliver sympathetic therapy. These devices received FDA clearance in March 2001 through a 510(k) process. The FDA-labeled indication is symptomatic relief of chronic intractable pain and/or management of post-traumatic or post-surgical pain.
Electroceutical therapy is also identified by several other names, including non-invasive neuron-blockade, bioelectric nerve block, bioelectric treatment, electroceutical neuron-blockade. This therapy is non-invasive, electrical-based treatment that is given for acute and chronic pain, e.g., fibromyalgia, back pain, neuropathy, joint pain, headache, or reflex sympathetic dystrophy. Electroceutical devices are similar to TENS in that they deliver stimulation through electrodes, or suction cups, attached to the skin; but they differ in that they use an electrical frequency many times higher than TENS. The proposed advantages of electroceutical therapy include relief of pain and reduction or elimination of pain medication. Examples of electroceutical devices may include CellGen HealthStation™ and PRO GeneSys System Electroceutical Treatment.
Other Types of Electrical Stimulation
Treatment of Osteoarthritis, e.g., BioniCare™ BIO-1000
Osteoarthritis is characterized by degeneration of articular cartilage with proliferation and remodeling of subchondral bone. Electrical stimulation has been used to improve functional status and relieve pain related to osteoarthritis and rheumatoid arthritis unresponsive to other standard therapies. Electrical stimulation is provided by an electronic device that noninvasively delivers a low-voltage, monophasic electrical field to the target site of pain. In basic research studies, pulsed electrical stimulation has been shown to alter chondrocyte-related gene expression in vitro and to have regenerative effects in animal models of cartilage injury.
The BioniCare™ BIO-1000 stimulator has received FDA clearance for marketing as a type of TENS device for use in osteoarthritis of the knee and rheumatoid arthritis of the hand. The BioniCare™ Bio-1000 consists of an electrical stimulation device with electrical leads that are placed on the knee and thigh, and held in place with a lightweight, flexible wrap and Velcro fasteners. The battery-powered device delivers small electrical currents of up to 12.0 volt output. The device is recommended to be worn for at least six hours per day; this can be done while sleeping.
The FDA’s 510(k) summary specifies that the BioniCare™ Stimulator, Model BIO-1000 is indicated for use as an adjunctive therapy in reducing the level of pain and for symptoms associated with both osteoarthritis of the knee and rheumatoid arthritis of the hand.
Cranial Electrotherapy Stimulation (CES)
Cranial electrotherapy stimulation (CES) is a category of FDA approved devices. A CES device applies electrical current to a patient's head to treat insomnia, depression, or anxiety. One example of a CES device is Alpha-Stim®, which uses microcurrent.
Treatment of Dysphagia, i.e., VitalStim™
VitalStim™ is a relatively new treatment for dysphasia (difficulty in swallowing), and is claimed to restore enough swallowing function to reduce or eliminate the need for tube feedings. With VitalStim™ therapy, electrical neuromuscular stimulation is delivered through electrodes attached to the skin of the throat, over the pharyngeal muscles; stimulation activates key swallowing muscles, which helps patients create or re-learn muscle function necessary for swallowing.
Electrical Stimulation as Treatment of Scoliosis
Scoliosis is a progressive lateral curvature of the spine, occurring in the thoracic region and/or lumbar spine. Neuromuscular electrical stimulation has been used as a treatment of idiopathic scoliosis to halt or reverse spinal curvature. This may be accomplished by either surface electrical stimulation of the lateral spinal musculature, or implanted deep muscle electrical stimulation to the paraspinal musculature. There are various stimulators that can be used to treat scoliosis; ScoliTron™ is one example.
A conductive garment is a form-fitted, lycra-spandex garment containing electrodes, wires, and connectors that greatly simplify electrical stimulation therapy. These are supplied in many forms, including sleeves for shoulder, arm, hip or leg; belts; shorts; vest; gloves; socks; or collar. These garments provide allowance for accurate placement of multiple electrodes without professional assistance, insurance that electrodes stay in position, and avoidance of skin irritation caused by adhesive on electrode pads. There are many brands and styles available; two examples are Bioflex Wearable Therapy System™ and RS-FBG® full back garment.