Ultrasound appearance of peripheral nerves in the neck: vagus, hypoglossal and greater auricular

Abstract

Background and aim. Information in ultrasonography about reference values of nerves, particularly of those located in the neck is limited. The aim of the study is to demonstrate the feasibility of direct visualization of the vagus, hypoglossal and greater auricular nerves, testing the method on healthy volunteers and estimate the reference values for two perpendicular diameters and cross-sectional area (CSA).
 Methods. A prospective study was carried out on 21 healthy volunteers (12 women and 9 men), recording their demographic characteristics. A 13 MHz transducer was used on a Hitachi EUB-8500 machine. The vagus nerve was measured at the bifurcation of common carotid artery (CCA) and at the intersection of the internal jugular vein with omohyoid muscle. The hypoglossal nerve was identified as it crosses the posterolateral border of the mylohyoid muscle in the submandibular space. The auricular nerve was identified on the superficial surface of the sternocleidomastoid muscle at 1 cm from its posterior margin. The mean CSA on axial scans, nerve width and thickness were determined. The side-to-side and gender differences of the estimated reference values and their correlations with the weight, height, and body mass index (BMI) were evaluated.
 Results. The mean ultrasound-estimated CSA was measured for the vagus nerve at CCA bifurcation (2.14 ± 0.79 on the left 2.86 ± 1.27 on the right), vagus nerve at the level of omohyoid muscle (2.10 ± 0.06 on the left and 2.43 ± 0.08 on the right), hypoglossal nerve (1.71 ± 0.08 on the left, 1.24 ± 0.06 on the right) and greater auricular nerve (0.90 ± 0.53 on the left and 0.79 ± 0.71 on the right). The vagus nerve was significantly larger on the right side compared to the left side. Larger hypoglossal nerve was observed in men compared to women. Significant correlations were observed between weight and CSA of the greater auricular nerve.
 Conclusion. Direct visualization of the vagus, greater auricular nerve and hypoglossal nerves is feasible. Reference values for the size of the studied nerves at specific anatomic landmarks were established. Side, gender and body weight differences of the nerves CSA were noted.

The cross-sectional area of the vagus nerve is not reduced in Parkinson’s Disease patients

“…The left vagus nuclei terminate in the anterior plexus and from there on new branches go to the stomach, liver and the superior part of the abdomen [16,27]. Fourth, the range of the CSA of the vagus nerve we found is similar to previous reports [16,19,25].…”

Ultrasound and magnetic resonance imaging evaluation of the femoral and sciatic nerves. A study of healthy volunteers

“…On the aggregate, more studies reported a correlation between BMI and size for different nerves of the upper and lower limbs [ 9 , 11 , 12 , 23 ]. In a recent study published by our group, focused on three nerves of the cervical region, we found a significant correlation for a particular one [ 29 ]. Both the differences between ultrasound and MRI measurements and the variable relationship with BMI may be explained by the measurement technique.…”

Prevalence and characteristics of vagus nerve variations on neck ultrasonography

“…In addition, VN variations were significantly more prevalent in the left side of the neck, with an approximately 10-fold higher proportion of variations compared to the right side (34.7% vs. 3.7%, P<0.001). These findings might be attributable to the left- to right-side difference in the anatomical course of the VN in the thorax and abdomen; moreover, the VN is the only paired nerve that innervates organs in a markedly asymmetric manner [ 13 , 14 ]. In the lower cervical region, the right VN crosses anterior to the right subclavian artery, runs posterior to the superior vena cava, and descends posterior to the right main bronchus.…”