Sonographic evaluation of the vagus nerves: Protocol, reference values, and side-to-side differences.

INTRODUCTION: Reported sonographic reference values for the vagus nerves (VNs) vary greatly. We aimed to generate reference values in a large cohort and examine intrarater, interrater, and across-ultrasound systems agreement.

METHODS: The VNs of 60 healthy subjects were examined by 2 sonographers and with 2 ultrasound systems. Cross-sectional areas (CSAs) of each VN were assessed at the level of the carotid sinus [proximal measurement level (ML)] and thyroid gland (distal ML).

RESULTS: Mean VN CSA was significantly larger on the right side (proximal ML: 2.7 ± 0.6 mm2 vs. 2.1 ± 0.5 mm2 ; distal ML: 2.6 ± 0.6 mm2 vs. 1.9 ± 0.4 mm2 ). VN CSA decreased with increasing age. There were good intrarater, interrater, and across-ultrasound systems agreements.

DISCUSSION: The right VN CSA is significantly larger than the left. These side- and age-specific reference values for the VN may be useful for future studies. Muscle Nerve 57: 766-771, 2018.