Sonographic Reference Values of Vagus Nerve: A Systematic Review and Meta-analysis.

PURPOSE: To establish the first comprehensive and standardized set of vagus nerve (VN) sonographic reference values across all the published studies that can be used to standardize and guide clinical practice and research. METHODS: This systematic review includes all possible available data from a total of 27 studies and 21 of them were included in the meta-analysis having a total of 864 participants. RESULTS: The overall mean cross-sectional area ranged from 2.29 to 2.76 mm2 for the right VN and from 1.83 to 2.23 mm2 for the left VN with 95% confidence interval. Sonographic reference values of VN at common carotid artery bifurcation, thyroid gland, and cartilage as well as other anatomic landmarks were provided. CONCLUSIONS: The mean cross-sectional area of the right VN of 2.53 mm2 and the left one of 2.03 mm2 can be considered as sonographic reference values in healthy adults. This review provides these reference values to be considered in the further sonographic evaluation of VNs.