Pulsed magnetic field therapy in refractory carpal tunnel syndrome: Electrodiagnostic parameters – pilot study

Abstract

Context:

Neuropathic pain arises from ectopic firing of nociceptors. Since pulsed electromagnetic fields (PEMF) generate extremely low frequency (ELF) quasi-rectangular currents which influence biological activity, it was hypothesized that directing this energy into the carpal tunnel region could influence neuronal firing patterns and lower VAS scores of neuropathic pain.

Objective:

To determine if nine consecutive one-hour treatments (excluding weekends) of a pulsed signal therapy can reduce neuropathic pain scores in refractory hands with carpal tunnel syndrome.

Design/setting/patients:

35 consecutive hands were enrolled in this non-placebo pilot study between July and November 2002. All subjects had to be constantly symptomatic and a failure to therapy. Primary endpoints were comparison of visual analog scores (VAS 0–10) at end of 9 days of treatment and end of 30 days follow-up compared to baseline pain scores. Additionally, at end of study, patients responded to a questionnaire (PGIC) describing their response to treatment. Secondary endpoints were comparison of sensory and motor distal latencies of median nerve after treatment with baseline. Additionally, clinical examination changes were tabulated with baseline. Five hands were surgical failures.

Intervention/device:

Non-invasive pulsed signal therapy generated a patented unidirectional quasi-rectangular waveform with strength less than 20 gauss and frequency less than 30 Hz into the carpal tunnel region for nine consecutive one-hour treatments (excluding weekends). The specific amount of energy directed at the target site was unknown.

Results:

Statistical reduction (ANOVA) of pain scores at end of treatment (23%) and also end of follow-up (37%) were noted in the 33 hands that completed the study. The PGIC questionnaire revealed 67% improvement. Clinical and electrodiagnostic examination data did not change from baseline to end of study. There were no adverse events or safety issues.

Conclusion:

Our pilot data suggests that directing PEMF to the carpal tunnel region can provide modest, short-term relief for a majority of individuals. The precise mechanism is unclear in the absence of electrophysiological changes. This provocative data requires confirmation with randomized, placebo-controlled, double-blind trials and additional electrophysiological markers.