Effect of Pulsed Electromagnetic Stimulation on Facial Nerve Regeneration

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Abstract
BIOLOGICAL stimulation by electromagnetic field exposures can modify cellular functions in bone and nervous tissue, and evidence is accumulating that the regeneration capacity of the tissue may be affected. For example, selective changes in levels of calcium,1 cyclic adenosine monophosphate,2 the synthesis of collagen and proteoglycans,3 DNA,4 and RNA5 have been demonstrated in osseous, nervous, and mesenchymal tissue. Pulsed electromagnetic fields have encouraged healing of fractured bones6 and benefited reanastomosis of peripheral nerves after transection. Wilson and Jagadeesh7 transected the ulnar nerve in rats and then applied pulsed electromagnetic stimulation for 15 minutes per day for 12, 30, 45, or 60 days. Rats receiving the highest stimulation had some return of nerve conduction at 30 days while rats receiving the lowest stimulation showed return of conduction only after 60 days. Ito and Bassett8 transected the sciatic nerve in rats and found a significant difference histologically and functionally at 4 weeks, with no difference in the 12– vs 24–hours per day stimulation time. Raji and Bowden9 also performed axotomy and immediate repair of the common peroneal nerve in rats. High-peak pulsed electromagnetic stimulation was delivered for 15 minutes per day at 3-day and 1-, 2-, 3-, 4-, and 8-week intervals. In the treated group, the time to functional recovery, as determined by leg use and the toe-spread reflex, was significantly quicker than in the control group at 12 and 21 days. Additionally, the pulsed electromagnetic stimulation group had less epineural thickening, less intraneural edema, increased size of intraneural blood vessels, and more mature myelination. Cordeiro et al10 transected the sciatic nerve in rats and used a nerve guide to bridge a 5-mm separation in the anastomosis. The rats were placed in high-energy static electromagnetic fields for 12 hours per day for 4 weeks. No difference was found in myelinated axon counts or in the latency of amplitude of the compound action potentials (CAPs) between treated and untreated rats. Orgel et al11 studied regeneration of the common peroneal nerve in cats during exposure to pulse-burst electromagnetic fields for 10 hours per day for 12 weeks. Although no nerve CAPs reached preoperative values, treated muscle CAPs did approach preoperative values. There was statistically significant improvement in labeling and localization of anterior horn cells in the central nervous system with the pulse-burst electromagnetic stimulation, but functional return was not examined.