External Branch of the Superior Laryngeal Nerve Mediated Glottic Closing Force in the Porcine Model

Objectives: Based on our laboratory's newly confirmed motor pathway for glottic closure, we measured the glottic closing force (GCF) during isolated stimulation of the external branch of the superior laryngeal nerve (eSLN) in the porcine model. Glottic closure is 1 of the primary mechanisms for prevention of aspiration during deglutition. Methods: The recurrent laryngeal nerve (RLN) and eSLN were identified bilaterally in 4 porcine necks. Subsequently, GCF was measured with a pressure transducer as the distal ends of individual nerves were stimulated in 4 animals. The RLN mediated GCF was measured first, followed by isolated eSLN mediated GCF, followed by transection of the RLN and repeat measurement of the eSLN GCF. Ultimately, the cricothyroid (CT) muscle attachment was released and the GCF measured. Results: The GCF during isolated eSLN stimulation before and after RLN transection is approximately 89% of the RLN mediated GCF in each animal. The GCF after CT release is approximately 84% of the RLN perceived GCF. Transection of the RLN did not alter the eSLN observed GCF. Conclusions: The GCF obtained during isolated eSLN stimulation is adequate for delivery of an appropriate laryngeal protective response and may be considered a target motor nerve for augmenting GCF in selected rehab settings.