Baertsch Hans C, Cvancara David, Bhatt Neel K
Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine University of Southern California Los Angeles California USA.
Department of Otolaryngology-Head and Neck Surgery University of Washington School of Medicine Seattle Washington USA.
Laryngoscope Investig Otolaryngol. 2023 May 4;8(3):739-745. doi: 10.1002/lio2.1071. eCollection 2023 Jun.
Age-related changes to the larynx are associated with dysphonia and contribute to reduced quality of life. This study utilizes recurrent laryngeal motor nerve conduction studies (rlMNCS) to determine if neurophysiologic changes occur in the aging larynx using an aging rat model.
Animal study.
In vivo rlMNCS were performed in 10 young hemi-larynges (3-4 months) and 10 aged hemi-larynges (18-19 months) rats (Fischer 344 × Brown Norway F344BN). Recording electrodes were placed into the thyroarytenoid (TA) muscle through direct laryngoscopy. Recurrent laryngeal nerves (RLNs) were directly stimulated with bipolar electrodes. Compound motor action potentials (CMAPs) were obtained. RLN cross-sections were stained with toluidine blue. Axon count, myelination, and g-ratio were quantified utilizing AxonDeepSeg analysis software.
rlMNCS were successfully obtained in all animals. Mean CMAP amplitude and negative durations in young rats were 3.58 ± 2.20 mV and 0.93 ± 0.14 mS (mean dif: 0.17; 95% CI: -2.21 to 2.54), respectively, and 3.74 ± 2.81 mV and 0.98 ± 0.11 mS (mean dif: 0.050; 95% CI: -0.07 to 0.17). No significant differences in onset latency or negative area were observed. Mean axon count in young rats (176 ± 35) was comparable to that in old rats (173 ± 31). Myelin thickness and g-ratio did not differ between groups.
There were no statistically significant differences in RLN conduction or axon histology between young and aged rats in this pilot study. This work provides a basis for future, adequately powered studies, and may lead to a tractable animal model to study the aging larynx.
喉部的年龄相关变化与发声障碍相关，并导致生活质量下降。本研究利用喉返运动神经传导研究（rlMNCS），通过衰老大鼠模型来确定衰老喉部是否发生神经生理学变化。
动物研究。
对10只年轻半喉（3 - 4个月）和10只老年半喉（18 - 19个月）大鼠（Fischer 344×Brown Norway F344BN）进行体内rlMNCS。通过直接喉镜检查将记录电极置于甲杓肌（TA）中。用双极电极直接刺激喉返神经（RLN）。获得复合运动动作电位（CMAP）。喉返神经横截面用甲苯胺蓝染色。利用AxonDeepSeg分析软件对轴突计数、髓鞘形成和g比值进行量化。
所有动物均成功获得rlMNCS。年轻大鼠的平均CMAP振幅和负向持续时间分别为3.58±2.20 mV和0.93±0.14 mS（平均差异：0.17；95%可信区间：-2.21至2.54），老年大鼠分别为3.74±2.81 mV和0.98±0.11 mS（平均差异：0.050；95%可信区间：-0.07至0.17）。在起始潜伏期或负向面积方面未观察到显著差异。年轻大鼠的平均轴突计数（176±35）与老年大鼠（173±31）相当。两组之间的髓鞘厚度和g比值没有差异。
在这项初步研究中，年轻和老年大鼠的喉返神经传导或轴突组织学方面没有统计学上的显著差异。这项工作为未来有足够样本量的研究提供了基础，并可能导致一种易于处理的动物模型来研究衰老喉部。
5级。
