Effect of pulsed electromagnetic stimulation on facial nerve regeneration.
OBJECTIVE
To determine if exposure to electromagnetic fields influences regeneration of the transected facial nerve in the rat.


METHODS
The left facial nerve was transected in the tympanic section of the fallopian canal in 24 rats randomly assigned to 2 groups. The cut ends of the facial nerve were reapproximated without sutures within the fallopian canal to maximize the potential for regeneration. Rats in the experimental group (n= 12) were then exposed to pulsed electromagnetic stimulation (0.4 millitesla at 120 Hz) for 4 hours per day, 5 days per week, for 8 weeks. Rats in the control group (n=12) were handled in an identical manner without pulsed electromagnetic stimulation. Four other rats were given sham operations in which all surgical procedures were carried out except for the actual nerve transection. Two of these rats were placed in each group. Nerve regeneration was evaluated using electroneurography (compound action potentials), force of whisker and eyelid movements, and voluntary facial movements before and at 2-week intervals after transection. Histological evaluation was performed at 10 weeks after transection. Each dependent variable was analyzed using a 2-way analysis of variance with 1 between variable (groups) and 1 within repeated measures variable (days after transection).


RESULTS
Statistical analysis indicated that N1 (the negative deflection of depolarization phase of the muscle and/or nerve fibers) area, N1 amplitude, and N1 duration, as well as absolute amplitude of the compound action potentials, were all significantly greater 2 weeks after transection in the experimental than in the control group of rats. The force of eye and whisker movements after electrical stimulation was statistically greater in the experimental group of rats 4 weeks after transection. Voluntary eye movements in the experimental group were significantly better at 5 and 10 weeks, while whisker movements were better at 3 and 10 weeks. There was no statistical difference between the 2 groups for any histological variable.


CONCLUSIONS
Results of this study indicate that pulsed electromagnetic stimulation enhances early regeneration of the transected facial nerve in rats.
Byers
J M
JM
Department of Otorhinolaryngology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.
Clark
K F
KF
Thompson
G C
GC
D000714:Anastomosis, Surgical; D000818:Animals; D004574:Electromagnetic Fields; D005152:Facial Muscles / Q000294:innervation; D005154:Facial Nerve / Q000528:radiation effects*; D008297:Male; D009119:Muscle Contraction / Q000528:radiation effects; D009416:Nerve Regeneration / Q000528:radiation effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000528:radiation effects