Response of pain to static magnetic fields in postpolio patients:
A double-blind pilot study.

By: Carlos Vallbona, MD, Carlton F. Hazlewood, PhD, Gabor Jurida, MD

ABSTRACT:
Vallbona C, Hazlewood CF, Jurida G.
Response of pain to static magnetic fields in postpolio patients: a double-blind pilot study. Arch Phys Med Rehabil 1997;78: 1200-3.

OBJECTIVE:
To determine if the chronic pain frequently presented by postpolio patients can be relieved by application of magnetic fields applied directly over an identified pain trigger point.

DESIGN:
Double-blind randomized clinical trial.

SETTING:
The postpolio clinic of a large rehabilitation hospital.

PATIENTS:
Fifty patients with diagnosed postpolio syndrome who reported muscular or arthritic-like pain.

INTERVENTION:
Application of active or placebo 300 to 500 Gauss magnetic devices to the affected area for 45 minutes.

MAIN OUTCOME MEASURE:
Score on the McGill Pain Questionnaire.

RESULTS:
Patients who received the active device experienced an average pain score decrease of 4.4 +- 3.1 (p < .0001) on a 10-point scale. Those with the placebo devices experienced a decrease of 1.1 +- 1.6 points (p < .005). The proportion of patients in the active-device group who reported a pain score decrease greater than the average placebo effect was 76%, compared with 19% in the placebo-device group (p < .0001).

CONCLUSIONS:
The application of a device delivering static magnetic fields of 300 to 500 Gauss over a pain trigger point results in significant and prompt relief of pain in postpolio subjects.

©1997 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

POSTPOLIO SYNDROME is a well-recognized clinical entity which, since the early 1980s, has generated an abundant scientific literature (a Medline search found 88 references from 1981 to 1996; 24 of the publications included pain as a key word). The clinical manifestations are either very specific (eg, increasing muscle weakness on previously affected or unaffected muscles, muscle fasciculations) or somewhat unspecific (eg, fatigue, pain).

The pain reported by postpolio patients can generally be categorized as either (1) myofascial, which can be elicited in various muscle groups, or (2) arthritic, which is evident on active or passive mobilization of several joints. In the initial report about the postpolio syndrome by Halstead and coworkers, the prevalence of pain among polio survivors who responded to a questionnaire was 75.5%. Subsequent reports confirm that many types of pain are experienced by postpolio patients, but most include diffuse muscle and joint pain. In our experience with more than 1,000 patients diagnosed with postpolio syndrome at postpolio clinic, pain is reported by almost all patients.

Pain in the joint is thought to result from degenerative arthritis caused by age and by longstanding asymmetrical load on the joints as a result of the asymmetrical skeletal muscle paresis or paralysis produced by poliomyelitis. The most common type of joint pain is referred to the low back, the cervical column, the sacroiliac joint. The last-named may be reported as diffuse low back pain but can be readily localized through palpation of a specific trigger point located above the sacroiliac joint. Hip and shoulder pain are also prevalent.

The muscular type of pain can be objectively elicited by palpation of the reported sore muscles and by identifying specific trigger points associated with the referred pain. The atlas of trigger points provided by Travell and Simons is of great aid in the search for such trigger points. Symptomatic cervical arthritis may be accompanied by a considerable degree of tightness of the neck muscles with trigger points in the sternocleidomastoid, scalenus, and trapezius areas.

Regardless of the type of pain, postpolio patients have increased sensitivity to nociceptive stimuli, and this may explain why they report pain so often. In spite of its prevalence the available treatment for it is limited. Currently, recommended modes of treatment are rest; traditional modalities of physical therapy (heat, cold, ultrasound, transcutaneous electrical neural stimulation (TENS); use of a support brace; or administration of muscle relaxants, analgesics, or anti-inflammatory agents. The effectiveness of pharmacologic agents is generally poor and in some instances (eg, use of aspirin or nonsteroidal antiinflammatory drugs) there are undesirable side effects. Other modalities of pain management such as meditation, yoga or hypnosis have not given our patients consistent relief.

The limited success in pain management prompted us to explore alternative methods of pain management. Static and fluctuating electromagnetic fields have been applied with apparent success for the management of pain in a variety of orthopedic conditions, most commonly traumatic bone fractures or surgical osteotomies. As early as 1938, Hansenreported the effectiveness of electromagnetic fields (which had a carrying power of from 8.5 to 14 kg) applied for 1 to 15 minutes. Twenty three of 26 patients with complaints of "sciatica," "lumbago" and "arthralgia" reported rapid and significant relief of their pain. The study was not double-blinded, but the author reported no pain reduction in two patients to whom the electromagnetic device was applied without the electricity being turned on. In osteoarthritis, double-blind, placebo-control studies have shown the efficacy of a pulsed electromagnetic field. Carpenter and Ayrapetyan provide an excellent overview of the biological effects of electromagnetic fields. The literature continues to grow from earlier reports, building on further efforts to scientifically document the impact of magnetic fields on biological systems. The safety of application of these electromagnetic fields is attested by the World Health Organization, which reported: "The available evidence indicates the absence of any adverse effects on human health due to exposure to static magnetic fields up to two Tesla" (2T = 20,000 Gauss).

Table 1: Characteristics of Study Patients

	Active Magnetized Device	Inactive Device
Number of subjects	29	21
Age (mean+-SD)	51.5 +- 9.6	55.9 +- 9.7
Sex (F:M)	24:5	15:6
Race–ethnicity (W, B, H, A)*	22, 1, 6, 0	18, 2, 0, 1
Weight (mean +- SD)	151.59 +- 31.05	151.79 +- 34.76
Age at onset of poliomyelitis (mean yrs +- SD)	6.34 +- 5.72	7.17 +- 6.79
Age at onset of postpolio syndrom (mean yrs +- SD)	42.84 +- 7.44	44.41 +- 7.10
Type of treated pain (M/A)†	52%/48%	43%/57%

* W, White; B, African-American; H, Hispanic; A, Asian, †M, Muscular; A, Arthritic.
Static magnetic fields can be delivered by placing magnets of different field strengths on the skin over the affected areas. These magnets usually vary in strength from 300 to 5,000 Gauss. The magnets can be kept in place with adhesive tape. A variety of magnets are commercially available. Frequently, significant pain relief has been observed less than 30 minutes after placement of the magnets. Anecdotal reports of the benefits of permanently magnetized devices abound (even in postpolio patients who had reported pain relief to us before our study). Nakagawa, in a technical bulletin, reported a decrease of neck and shoulder pain after use of a loosely fitted magnetically active necklace. However, Hong and associates did a double-blind study of the long-term effect of a similar device on some physiologic parameters (nerve conduction velocity and excitation threshold) in a group of 101 volunteers, but did not find any significant pain relief in the 52 who had reported chronic neck or shoulder pain before the study when compared with the 48 who had not reported pain.

To our knowledge, static magnetic fields (electromagnetic or permanently magnetized devices) have not been scientifically tested on postpolio survivors. Consequently, we completed a double-blind pilot study on patients at our clinic who reported significant muscular or arthritic-type pain.