Reference Values of the Tube-Based Laryngeal Adductor Reflex of the Healthy Recurrent Laryngeal Nerve

This study aimed to establish reference values for laryngeal adductor reflex latency and amplitude under general anesthesia using a noninvasive technique with commercially available electromyographic endotracheal tubes.

This retrospective observational study included 380 patients undergoing head and neck surgery. The inclusion criteria were recording the laryngeal adductor reflex from the nonsurgical side and the absence of pathology in the recurrent laryngeal nerve. Measurements were taken before incision and surgical completion.

The R1 component medians for the latency and amplitude were 20 ms and 448 µV for the right and 22 ms and 425 µV for the left LARs, respectively. There were significant differences in the R1 latencies between the sides. Quantile regression models revealed that 95th percentile amplitudes exceeded 400 µV, whereas 5% of our data set surpassed 600 µV. The R2 component was present in 26% of patients initially but decreased to 8% at surgical conclusion. The percentage difference between the median R1 value at the end of the surgery, compared with the opening value, was up to 4% for latency and 10% for amplitude.

The R1 component of the laryngeal adductor reflex remains a reliable tool for intraoperative neuromonitoring. This is the largest study to provide reference values for laryngeal adductor reflex, aiding future diagnostic applications in head and neck surgeries.