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Abstract: Aim: This study aims to determine the influencing factors in the positioning of the vocal fold (VF) in cases of paralysis of the recurrent and superior laryngeal nerves (RLN, SLN). Material and methods: VF paralysis was caused in rats according to the following procedures: Group A: 20 rats were cut at different sites of the RLN. Group B: 15 rats were cut at the R1.N and cricothyroid muscle fibers. Group C: 7 rats had the RLN cutoff, according to the VF movelnent in the breathing cycle. Discussion: In most cases, the Ws were still in paraimedian position even when the cricothyroid muscle fibers were se sectioned or the muscle denervated. In 20% of the rats, which underwent muscle denervation, the VF's were still laterally positioned. In those cases, when the RLN's were cut following the breathing cycle, the vocal fold was in paramedian position, even when the cut was made in the inspiratoy phase of the breathing cycle. In this case, the VF, then in abdution, quickly moves to the median line, as in was being, pulled. Conclusion: We conclude that the VF position in rats is independent of 1. the cricothyroid muscle action; 2. the site of the lesion in the RLN; and 3. phase of the breathing cycle in which the lesion occurs.
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