Observation on the regeneration of axonotmesis rat facial nerve exposed to low-intensity microwave radiation

ABSTRACT

The effect of low-intensity microwave radiation on the regeneration of an axonotmised facial nerve was studied in 40 male Wistar rats. A compression of 40 +/- 3 N was applied to the extramastoid portion of the nerve trunk for 10 min. After the release of compression, 20 animals were irradiated in the far field for 2 h per day at a frequency of 2.45 GHz and an incident power density of 18.2 +/- 1.4mW/cm2 [SAR 1.4 W/kg]. The remaining animals were sham-irradiated and used as controls. The effect of irradiation treatment was assessed by determining the time at which recovery started by morphometric analysis and by the restoration of motor function. Irradiated animals recovered earlier than control animals and possessed a greater number of Schwann cells after 4 and 8 days. There was a significant increase in the relative number of myelinated nerve fibers after 8, 12 and 16 days of treatment. The average thickness of myelin sheaths was significantly greater in irradiated animals at 12 days. The difference observed between treated and control animals in the morphologic parameters suggests that irradiation treatments have promoted recovery through enhancement of nerve regeneration