Even weak AC magnetic fields affect pain perception and pain-related EEG changes in humans. A 2 hour exposure to 0.2-0.7G ELF magnetic fields caused a significant decrease in pain-related EEG patterns.
Pain relief mechanisms vary by the type of stimulus used. For example, needling to the pain-producing muscle, application of a static magnetic field or external qigong or needling to an acupuncture point all reduce pain but by different mechanisms. Pain could be induced by reduction of circulation in muscle and reduced by recovery of circulation. Pain mediating substances are accumulated in a muscle under reduced circulation and reversed with restoration of circulation. This is why chronic muscle tension is a frequent cause of chronic pain. The effect of a static magnetic field or external qigong is mediated by enhanced release of acetylcholine as a result of activation of the cholinergic vasodilator nerve endings in a muscle artery. Needling an acupuncture point is probably induced by a somato-autonomic reflex through the brain, in the anterior hypothalamus.
In normal subjects, a magnetic stimulus over the cerebellum reduces the size of responses evoked by cortical stimulation. Suppression of motor cortical excitability is reduced or absent in patients with a lesion in the cerebellum or cerebellar nerve pathways. Magnetic stimulation over the cerebellum produces the same effect as electrical stimulation, even in ataxic patients and may be useful for the pain associated with muscle spasticity.
Clinical benefits
In diabetic neuropathy, PEMF treatment every day for about 12 minutes, improves pain, paresthesias and vibration sensation and increases muscular strength in 85% of patients compared to controls.
One author reported that, of treated patients followed for 2-60 months, better results happened in patients with post-herpetic pain and those simultaneously suffering from neck and low back pain.
Chronic pain is often accompanied with or results from decreased circulation or perfusion to the affected tissues, for example, cardiac angina or intermittent claudication. PEMFs have been shown to improve circulation. Skin infrared radiation increases due to immediate vasodilation with low frequency fields and increased cerebral blood perfusion in animals. Pain syndromes due to muscle tension and neuralgias improve.
The results of the treatment depend not only on the parameters of the fields but also on the individual sensitivity of the person. The most effective results in clinical use were found with extremely ultra low frequency PEMFs.
Back, neck and shoulder pain
Chronic low back pain affects approximately 15% of the United States (US) population during their lifetime, with 93 million lost work days and a cost of more than $5 billion per year. Lumbar arthritis is a very common cause of back pain. 35-40 mT PEMFs, for 20 minutes daily for 20-25 days for back pain gives relief or elimination of pain, improves results from other rehabilitation and improves secondary neurologic symptoms. Continuous use over the treatment episode works best, in about 90-95% of the time. Control patients only show a 30% improvement.
PEMF of 5 to 15 G, from 7 Hz to 4 kHz used at the site of pain and related trigger points for 20 to 45 minutes also helps. Some patients remain pain free 6 months after treatment. Some return to jobs they had been unable to perform. Short term effects are thought due to decrease in cortisol and noradrenaline and an increase serotonin, endorphins and enkephalins. Longer term effects may be due to CNS and/or peripheral nervous system biochemical and neuronal effects in which correction of pain messages occurs and the pain is not just masked as in the case of medication.
Back pain or whiplash syndrome treated PEMF twice a day for two weeks along with usual pain medications relieves pain in 8 days vs. 12 days in the controls. Headache is halved in the PEMF group and neck and shoulder/arm pain improved by one third versus just medications alone.
Permanent magnetic therapy can also be useful in reducing chronic muscular low back pain. Treatment with a flexible permanent magnetic pad for 21 days reduces pain 6 times more than placebo. This has been effective for herniated lumbar discs, spondylosis, radiculopathy, sciatica and arthritis. Pain relief is sometimes experienced as early as 10 minutes or in some cases takes as long as 14 days.
Low-power pulsed short wave 27 Hz diathermy has successfully treated persistent neck pain and improved mobility. The neck pains lasted longer than 8 wk and did respond to at least 1 course of nonsteroidal anti-inflammatory drugs. A miniaturized, 9V battery-operated, diathermy generator was fitted into a soft cervical collar. Treatment is for 3-6 weeks, 8 hr daily. Analgesics can be used as needed and nonsteroidal anti-inflammatory drugs. 75% of patients improve in range of motion and pain within 3 wk of treatment.
For neck pain, PEMFs may have more benefit, compared to physical therapy, for both pain and mobility.
Other pain applications
High frequency PEMF of 10-15 single treatments every other day either eliminates or improves, even at 2 weeks following therapy, 80% of patients with pelvic inflammatory disease, 89% with back pain, 40% with endometriosis, 80% with postoperative pain, and 83% with lower abdominal pain of unknown cause.
In dentistry, PEMFs have also been found only slightly useful in treating dental pain, jaw muscle spasms and swelling during wisdom tooth extraction with a high frequency system. As is often seen in pain studies, a placebo response is high, 30-40% of the time. In periodontal disease bone resorption may be severe enough to require bone grafting. Grafting is followed by moderate pain peaking several hours afterwards. Repeated PEMF exposure for two weeks eliminates pain within a week. Even single PEMF exposure to the face for 30 minutes of a 5mT field and conservative treatment produces much lower pain scores vs. controls.
Pelvic pain of gynecological origin was also found to be benefited by a different high voltage, high frequency system. This includes ruptured ovarian cysts, postoperative pelvic hematomas, chronic urinary tract infection, uterine fibrosis, dyspareunia, endometriosis and dysmenorrhea. Treatment times vary from 15 to 30 minutes on subsequent or alternate days. 90% of patients experience marked, rapid relief from pain with pain subsiding within 1-3 days. Most of these patients don’t require supplementary analgesics.
Post-herpetic neuralgia (PHN), a very common and painful condition, which is often medically-resistant, responds to PEMF for 20-30 minutes daily for 19 treatments over 34 days. The PEMF is a 4-16 Hz and 0.6-T samarium/cobalt magnet system surrounded by spiral coil pads with a maximum 0.1-T pulse at 8 Hz pasted on the pain/paresthesia areas or over the spinal column or limbs. Treatments continue until symptoms improve or an adverse side effect occurred. PEMF therapy is effective in 80%. No pain was made worse. This treatment approach shows that treatment for pain problems may either be localized to the pain or done over the spinal column or limbs, away from the pain.
PEMFs applied to the inner thighs for at least 2 wk is effective short-term therapy for migraine. Greater reduction of headache activity is achievable with longer exposure. PEMF using a high frequency signal to the inner thigh femoral artery area for 1 hr/day, 5 day/wk, for 2 weeks decreases headache. One month after a treatment course, 73% of patients report decreased headache activity vs. only half of those receiving placebo treatment. Another 2-wk of treatment after the 1-month follow-up gives an additional 88% decrease in headache activity. If there is no additional treatment after an initial course 72% still show a benefit. Placebo patients getting active treatment afterwards report much better additional improvement in headache.
Patients suffering from headache treated with a PEMF after failing acupuncture and medications, applied to the whole body, 20 min/day for 15 days get effective relief of migraine, tension and cervical headaches at about one month after treatment. They have at least a 50% reduction in frequency or intensity of the headaches and reduction in analgesic drug use. Poor results are seen in cluster and posttraumatic headache.
Chronic pain frequently presented by postpolio patients can be relieved by application of magnetic fields applied directly over trigger points using 300 to 500 G static magnets for 45 minutes.
Orthopedic or musculoskeletal uses
The use of PEMFs is rapidly increasing and extending to soft tissue from its first applications to hard tissue. EMF in current orthopedic clinical practice is used to treat delayed and non-union fractures, rotator cuff tendinitis, spinal fusions and avascular necrosis, all of which can be very painful. Clinically relevant response to the PEMF is generally not always immediate, requiring daily treatment for several months in the case of non-union fractures. PEMF signals induce maximum electric fields in the mV/cm range at frequencies below 5 kHz. Pulse radiofrequency fields (PRF) consist of bursts of sinusoidal waves in the short wave band, usually in the 14-30 MHz range. PRF induces fields in the V/cm range. PRF signals have higher field strengths than PEMFs. PRF signals have low frequency bursts nearly equivalent in size to PEMFs. This means that PRF signals have a broader band. PRF applications are best for reduction of pain and edema. The tissue inflammation that accompanies the majority of traumatic and chronic injuries is essential to the healing process, however the body often over-responds and the resulting edema causes delayed healing and pain. For soft tissue and musculoskeletal injuries and post-surgical, post-traumatic and chronic wounds, reduction of edema is thus a major therapeutic goal to accelerate healing and associated pain. Double-blind clinical studies have now been reported for chronic wound repair, acute ankle sprains, and acute whiplash injuries. PRFs accelerated reduction of edema in acute ankle sprains by 5-fold. Response to MFs is during or immediately after treatment of acute injuries. Responses are significantly slower for bone repair. The voltage changes induced by PRF at binding sites in macromolecules affect ion binding kinetics with resultant modulation of biochemical cascades relevant to the inflammatory stages of tissue repair.
High strength repetitive magnetic stimulation (rMS) has been found to relieve musculoskeletal pain. Specific diagnoses were painful shoulder with abnormal supraspinatus tendon, tennis elbow, ulnar compression syndrome, carpal tunnel syndrome, semilunar bone injury, traumatic amputation neuroma of the median nerve, persistent muscle spasm of the upper and lower back, inner hamstring tendinitis, patellofemoral arthrosis, osteochondral lesion of the heel and posterior tibial tendinitis. Patients receive rMS for 40 minutes. Mean pain intensity is 59% lower vs. 14% for controls. Patients with amputation neuroma and patellofemoral arthritis obtain no benefit. Those with upper back muscle spasms, rotator cuff injury and osteochondral heel lesions showed more than 85% decrease in pain, even after a single rMS session. Pain relief persists for several days. None have worsening of their pain.
Osteoarthritis (OA) affects about 40 million people in the USA. OA of the knee is a leading cause of disability in the elderly. Medical management is often ineffective and creates additional side-effect risks. The QRS has been in use for about 20 years in Europe. The QRS applied 8 min twice a day for 6 weeks improves knee function and walking ability significantly. Pain, general condition and well-being also improve. Medication use decreases and plasma fibrinogen decreases 14%, C-reactive protein ( a sign of inflammation) drops 35% and the blood sedimentation rate 19%. The QRS has also been found effective in degenerative arthritis, pain syndrome and inflammatory joint disorders. Sleep disturbances often contribute to increased pain perception. The QRS has also been found to improve sleep. 68% report good/very good results. Even after one year follow-up, 85% claim a continuing benefit in pain reduction. Medication consumption decreases from 39% at 8 weeks to 88% after 8 weeks.