November 15, 2008

A randomized controlled trial of the effects of a combination of static and dynamic magnetic fields on carpal tunnel syndrome. (magnetic therapy jewelry)

A randomized controlled trial of the effects of a combination of static and dynamic magnetic fields on carpal tunnel syndrome.

Pain Med. 2008 Jul-Aug;9(5):493-504

Authors: Weintraub MI, Cole SP

OBJECTIVE: To determine if a physics-based combination of simultaneous static and time-varying dynamic magnetic field stimulation to the wrist 4 hours/day for 2 months can reduce subjective neuropathic pain and influence objective electrophysiologic parameters of patients with carpal tunnel syndrome (CTS). METHODS: Randomized, double-blinded, placebo-controlled trial of 36 symptomatic hands. Primary endpoints were visual analog scale (VAS) and neuropathic pain scale (NPS) scores at baseline and 2 months and a Patient's Global Impression of Change (PGIC) questionnaire at the end of 2 months. Secondary endpoints were neurologic examination, median nerve distal latencies (compound muscle action potential CMAP/sensory nerve action potential SNAP), dynamometry, pinch gauge readings, and current perception threshold (CPT) scores. An "active" device was provided gratis at the end of the study, with 15 subjects voluntarily remaining within the open protocol an additional 2-10 months and using the preselected primary and secondary parameters. RESULTS: (two months). Of the 31 hands, 25 (13 magnet, 12 sham) had moderate to severe pain (VAS > 4). The VAS and PGIC revealed a nonsignificant pain reduction. NPS analyses (anova) demonstrated a statistically significant reduction of "deep" pain (35% downward arrow vs 12% upward arrow, P = 0.018), NPS Total Composite (decreases of 42% vs 24%, P = 0.042), NPS Total Descriptor Score (NPS 8; 43% vs 24%), and NPS 4 (42% vs 11%). Motor strength, CMAP/SNAP, and CPT scores were not significantly changed. Of the 15 hands with up to 10 months of active PEMF (pulsed electromagnetic fields) exposure, there was objective improvement in nerve conduction (CMAP = 53%, SNAP = 40%, >1 SD), and subjective improvement on examination (40%), pain scores (50%), and PGIC (70%). No detectable changes in motor strength and CPT. CONCLUSIONS: PEMF exposure in refractory CTS provides statistically significant short- and longterm pain reduction and mild improvement in objective neuronal functions. Neuromodulation appears to influence nociceptive-C and large A-fiber functions, probably through ion/ligand binding.

PMID: 18777606 PubMed - indexed for MEDLINE

Magnetic resonance acoustic radiation force imaging.

Med Phys. 2008 Aug;35(8):3748-58

Authors: McDannold N, Maier SE

Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are "stiffness weighted" and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery.

PMID: 18777934 PubMed - indexed for MEDLINE

Pulsed Magnetic Therapy