Establishment of recurrent laryngeal nerve injury animal models using intraoperative neural monitoring: SD rat models.

OBJECTIVE: To reproduce the Sprague Dawley (SD) rat model of recurrent laryngeal nerve (RLN) injury using intraoperative neural monitoring (IONM), this study investigates its key focuses, challenges and solutions, verifies the reproducibility of the established porcine model in rats, and evaluates the feasibility of the SD rat model as an alternative to the porcine model. METHODS: Twenty-four SD rats weighing 200-250 g were selected. Anesthesia was induced with 3%-5% isoflurane in oxygen at a flow rate of 1 L/min, and then maintained with 1.5%-2.5% isoflurane in oxygen at a flow rate of 0.2-0.4 L/min. Following cervical depilation, surgical disinfection, and midline cervical incision, surgeons exposed the trachea, thyroid gland, and RLN. Rats were randomized into three groups (n=8 each, 8 RLNs per group): traction injury, clamping injury, and transection injury, simulating intraoperative RLN trauma. A rat-specific electronic fiberoptic transoral laryngoscope was employed to observe vocal cord movement before and after surgery. Laryngoscopic re-examinations were performed weekly within 4 weeks after surgery, and the results were compared with the preoperative data. RESULTS: Preoperatively, all rats had normal bilateral vocal cord movement. Within 3 postoperative weeks, all groups showed unilateral vocal cord paralysis or incomplete glottic closure. At 4 weeks, vocal cord function fully recovered in the traction group and a small number of the clamping group, but remained impaired in most clamping rats and all transection rats. All injuries caused reduced or lost RLN electromyography (EMG) signals, electrophysiological recovery was consistent with vocal cord improvement. CONCLUSIONS: Preliminary data showed similar EMG trends after traction injury in SD rats and porcine models, supporting its potential as an alternative model for further validation. The SD rat model has advantages of fast modeling and low cost, and its challenges including surgical difficulty, IONM and laryngoscopic issues can be solved by optimized surgical methods.