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Response of pain to static magnetic fields in postpolio
patients:
A double-blind pilot study
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, Hansen reported 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
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Active Magnetized
Device
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Inactive Device
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No. of subjects
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29
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21
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Age (mean+-SD)
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51.5 +- 9.6
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55.9 +- 9.7
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Sex (F:M)
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24:5
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15:6
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Race–ethnicity (W, B, H, A)*
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22, 1, 6, 0
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18, 2, 0, 1
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Weight (mean +- SD)
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151.59 +- 31.05
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151.79 +- 34.76
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Age at onset of poliomyelitis (mean yrs +- SD)
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6.34 +- 5.72
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7.17 +- 6.79
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Age at onset of postpolio syndrom (mean yrs +- SD)
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42.84 +- 7.44
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44.41 +- 7.10
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Type of treated pain (M/A)†
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52%/48%
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43%/57%
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*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.
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