magnetic field therapy in refractory neuropathic pain secondary to peripheral neuropathy

[Guest guest]

Abstract from Neurorehabil Neural Repair. 2004 Mar;18(1):42-6.

Pulsed magnetic field therapy in refractory neuropathic pain secondary

to peripheral neuropathy: electrodiagnostic parameters-pilot study.

Weintraub MI, Cole SP.

New York Medical College, Briarcliff Manor, New York 10510.

Context: Neuropathic pain (NP) from peripheral neuropathy (PN) arises

from ectopic firing of unmyelinated C-fibers with accumulation of sodium

and calcium channels. Because pulsed electromagnetic fields (PEMF)

safely induce extremely low frequency (ELF) quasirectangular currents

that can depolarize, repolarize, and hyperpolarize neurons, it was

hypothesized that directing this energy into the sole of one foot could

potentially modulate neuropathic pain.

OBJECTIVE: To determine if 9 consecutive 1-h treatments in physician's

office (excluding weekends) of a pulsed signal therapy can reduce NP

scores in refractory feet with PN. Design/setting/patients: 24

consecutive patients with refractory and symptomatic PN from diabetes,

chronic inflammatory demyelinating polyneuropathy (CIDP), pernicious

anemia, mercury poisoning, paraneoplastic syndrome, tarsal tunnel, and

idiopathic sensory neuropathy were enrolled in this nonplacebo pilot

study. The most symptomatic foot received therapy. Primary endpoints

were comparison of VAS scores at the end of 9 days and the end of 30

days follow-up compared to baseline pain scores. Additionally, Patients'

Global Impression of Change (PGIC) questionnaire was tabulated

describing response to treatment. Subgroup analysis of nerve conduction

scores, quantified sensory testing (QST), and serial examination changes

were also tabulated. Subgroup classification of pain (Serlin) was

utilized to determine if there were disproportionate responses.

INTERVENTION: Noninvasive pulsed signal therapy generates a

unidirectional quasirectangular waveform with strength about 20 gauss

and a frequency about 30 Hz into the soles of the feet for 9 consecutive

1-h treatments (excluding weekends). The most symptomatic foot of each

patient was treated. RESULTS: All 24 feet completed 9 days of treatment.

15/24 completed follow-up (62%) with mean pain scores decreasing 21%

from baseline to end of treatment (P = 0.19) but with 49% reduction of

pain scores from baseline to end of follow-up (P < 0.01). Of this group,

self-reported PGIC was improved 67% (n = 10) and no change was 33% (n =

5). An intent-to-treat analysis based on all 24 feet demonstrated a 19%

reduction in pain scores from baseline to end of treatment (P = 0.10)

and a 37% decrease from baseline to end of follow-up (P < 0.01).

Subgroup analysis revealed 5 patients with mild pain with nonsignificant

reduction at end of follow-up. Of the 19 feet with moderate to severe

pain, there was a 28% reduction from baseline to end of treatment (P <

0.05) and a 39% decrease from baseline to end of follow-up (P < 0.01).

Benefit was better in those patients with axonal changes and advanced

CPT baseline scores. The clinical examination did not change. There were

no adverse events or safety issues.

CONCLUSIONS: These pilot data demonstrate that directing PEMF to

refractory feet can provide unexpected shortterm analgesic effects in

more than 50% of individuals. The role of placebo is not known and was

not tested. The precise mechanism is unclear yet suggests that severe

and advanced cases are more magnetically sensitive. Future studies are

needed with randomized placebo-controlled design and longer treatment

periods.