Donor-Derived Fibrin Matrix as an Adjunct to Microsurgical Recurrent Laryngeal Nerve Repair: An Experimental Rat Study

Background/Objectives: Recurrent laryngeal nerve (RLN) transection may cause persistent vocal fold dysfunction despite microsurgical reconstruction. Biological scaffolds may support nerve healing and preserve target muscle. This study evaluated a donor-derived fibrin matrix as an adjunct to primary microsurgical RLN repair in rats. Methods: 27 female Wistar albino rats were assigned to three groups (n = 9 each): RLN transection without repair, primary end-to-end microsurgical repair, and identical repair supplemented with donor-derived fibrin matrix. Vocal fold mobility was assessed by laryngoscopy after 3 months. Vocal fold muscle atrophy and histopathological changes at the RLN injury/repair site were evaluated. Results: Vocal fold mobility was observed in 0/9, 2/9, and 4/9 animals, respectively, without a significant between-group difference (p = 0.116). Vocal fold muscle atrophy differed significantly among groups (p < 0.001). Severe atrophy occurred in all animals in the transection group and in 4/9 after primary repair, whereas no severe atrophy occurred in the fibrin matrix group; 7/9 animals in this group had no atrophy. Significant group differences were also observed for inflammation (p = 0.003), edema (p = 0.008), fascicular organization disorder (p < 0.001), and foreign-body reaction (p < 0.001). Axon counts did not differ significantly (p = 0.085). Conclusions: Donor-derived fibrin matrix supplementation was associated with reduced vocal fold muscle atrophy and more favorable histopathological findings after microsurgical RLN repair. Although vocal fold mobility was numerically higher in the fibrin matrix group, the difference was not statistically significant; therefore, no definitive improvement in functional recovery can be concluded. These findings suggest a potential structural benefit of fibrin matrix supplementation and warrant further investigation in larger studies with more sensitive functional assessments.