Short and Long Term Exposure to Unique, Time-Varying Pulsed Electro-Magnetic Fields in Refractory Carpal Tunnel Syndrome

INTRODUCTION:

Entrapment of the median nerve at the wrist is the most common cause of sensory and motor disturbance in the hands and can be progressively disabling.1,2 Complex mechanisms of compression and ischemia exist that adversely influence the large A myelinated fibers and small unmyelinated nociceptive C fibers. From a pathophysiological standpoint, neuropathic pain (numbness, tingling and burning, NP) is believed secondary to ectopic firing of nociceptive afferent unmyelinated C-fiber axons that are undergoing degeneration.3 Microneurography has confirmed that dysregulated expression of sodium and calcium channels, which accumulate at site of injury, are responsible for ectopic depolarization.3,4,53,54 When conventional therapy of splinting and pharmacotherapy fail, surgical decompression has been offered for moderate-severe cases. While usually successful, it is associated with significant complications, limitations and costs.5,6,7 Thus, the search for reliable and new therapeutic strategies is appealing.

Substantial evidence exists that time-varying magnetic fields produce biological effects by safely inducing extremely low-frequency (ELF) small electrical eddy currents within the tissues that can depolarize, repolarize and hyperpolarize neurons.8,9,10,11,12

Prior pilot data using static13 and pulsed magnetic fields (PEMF)14,15 directed to the carpal tunnel region significantly reduced NP. Since a new, novel device became commercially available that produced a combination of static and time-varying magnetic fields simultaneously, it was hypothesized that this energy could be directed into the wrists and potentially influence not only NP scores, but also modulate neuronal distal latencies (neurotransmission).

DEVICE:

DESCRIPTION: (FIGURE 1) This patented device (Biaxial Super Mini [Mx2R] by Nikken, Inc.) measures 2" in diameter and 1" in height and is worn with a Velcro strap similar to a wristwatch. It is noiseless and nonthermal. Its main component is a spherical permanent magnet, 1150G, 3/8" in diameter that rotates in two perpendicular directions simultaneously producing biaxial magnetic rotation (MX2R) and oscillating polarities up to 1,200 rpm-20 times per second. It is driven by a 2 V DC micro-motor which is shielded one inch away and produces a negligible back EMF. The device is powered by three ¼ AAA rechargeable NiMH (Nickel Metal Hydride) batteries

Randomized double blind placebo-controlled device with primary parameters of pain and sleep interupption scores, NPS scale and secondary parameters of neurological exam changes, nerve conduction latencies of median nerve, dynamometry, finger gauge pressures, CPT and PGIC were compared at baseline and end of two months. Patients were given a free "active" device gratis at end of study.

Inclusion criteria

• Intractable neuropathic pain in median nerve innervated hand for at least 3 months;
• Abnormal neurological examination compatible with diagnosis of CTS

Exclusion criteria

• Post-surgical failures,
• Pregnancy,
• Pts with pacemaker