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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Race–ethnicity (W, B, H, A)*
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Age at onset of poliomyelitis (mean yrs +- SD)
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Age at onset of postpolio syndrom (mean yrs +- SD)
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Type of treated pain (M/A)†
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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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