Recordings of Superior Laryngeal Nerve Sensory Nerve Action Potentials in a Rat Model.

ABSTRACT

OBJECTIVE: Superior laryngeal nerve (SLN) function is critical to laryngeal sensation. Sensory dysfunction in the larynx, mediated through the internal branch of the superior laryngeal nerve (iSLN), is thought to occur with aging and neurodegenerative disease. However, objective analysis of iSLN neurophysiology is difficult due to its anatomic location and small diameter. This study measures sensory nerve action potentials (SNAP) from the iSLN in a rat model. METHODS: SNAP data were obtained from two adult rat strains (Sprague-Dawley, SD and Fischer 344 × Brown Norway F1 Hybrid rats, FBN). Evoked responses were obtained by stimulating the main trunk of the SLN and recording the response using a 160-µm cuff electrode placed around the iSLN. SNAP were averaged from 10 stimulations. Laryngeal adductor reflex (LAR) threshold measurements were obtained with stimulation of the iSLN and direct laryngoscopy. The sections of the iSLN were obtained for histologic analysis. RESULTS: SLN-evoked responses were successfully obtained in 18 hemi-laryngeal preparations (SD n = 13 and FBN n = 5) with corresponding LAR threshold measurements. Mean(±SD) SNAP latency, total duration, amplitude, negative durations, and intensity were 2.28 ms (±0.56), 2.13 ms (±0.70), 879 µV (±535), and 0.69 mA (±0.25), respectively. SLN stimulation threshold to elicit an LAR was of 0.84 mA (±0.31). CONCLUSION: It is feasible to record evoked SLN responses in two adult rat strains. This work may lead to a tractable animal model for objective measurements of SLN neurophysiology with various disease states. LEVEL OF EVIDENCE N/A Laryngoscope, 2024.