By compressing the extratemporal facial nerve of guinea pigs, the author succeeded in pro-ducing the reversible palsy of the facial nerve.
The process and recovery of the palsy were assessed by evoked electromyogram of the orbicularis oculi muscle, and by blink reflex elicited by air puff. Nerve specimens obtained from the compressed site were examined under light microscope. In this experiment, the com-pression force was 1.6 kgW and the width of compressed area was 1.0mm. The duration of compression varied from one to 30 seconds.
In the first experiment, the author produced the palsy of a relatively short duration. The palsy was not induced by the compression of less than 5 seconds. After the compression from 5 to 15 seconds conductivity of the nerve remained for 24 hours, and then it was lost in 27 guinea pigs among 30. Three different types of the electromyographic response were observed
during 24 hours after the compression. However, no significant histological difference in the findings of myelin was found among these three types. The compression for 5 seconds resulted in the palsy for average 16 days in 15 guinea pigs without exception.
In the second experiment, the therapeutic effect of steroid hormone was investigated using 20 guinea pigs in which the nerve was compressed for 5 seconds. In 10 guinea pigs, methyl-
prednisolone acetate was injected 20mg/kg intramuscularly immediately after the compression and once every week. In 10 control guinea pigs, the same amount of physiological saline was injected in the same manner. In the steroid group, the blink reflex was restored significantly earlier than in control. The evoked electromyographic response in the steroid group appeared about one week earlier than in control. Histologically, the remyelinative process progressed earlier in the steroid group than in control.
Based on both experimental studies, it can be concluded that the compression for 5 seconds
is thought to be appropriate to investigate the therapeutic effect of different modality of treat-ment. Injection of steroid hormone accelerates repair of mechanical injury of the nerve.
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