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.

Correlation between sonographic morphology and function of the cervical vagus nerves.

The heart receives parasympathetic and to a lesser degree sympathetic input via the vagus nerve. Here, we investigated whether morphological changes of the cervical vagus nerves (VN) as assessed by high-resolution ultrasound (HRUS) correlated with the autonomic cardiac innervation. Measurement of heart rate variability (HRV) and HRUS of the VNs were performed in 88 healthy subjects (50 female; mean age 56 ±â€¯18 years). HRV parameters and the cross-sectional area (CSA) of the VNs correlated both inversely with age. We also found an inverse correlation between the left VN-CSA and HRV as well as parasympathetic parameters. The results imply an asymmetric parasympathetic (vagal) innervation of the heart.

Axonal Degeneration of the Vagus Nerve in Parkinson's Disease-A High-Resolution Ultrasound Study.

Background: Recent histopathological studies revealed degeneration of the dorsal motor nucleus early in the course of Parkinson's disease (PD). Degeneration of the vagus nerve (VN) axons following neurodegeneration of brainstem vagal nuclei should be detectable by high-resolution ultrasound (HRUS) as a thinning of the VNs. Methods: We measured both VNs cross-sectional area (VN-CSA) of 35 patients with PD and 35 age- and sex-matched healthy controls at the level of the thyroid gland using HRUS. Results: On both sides, the VN-CSA was significantly smaller in PD patients than in controls (right: 2.1 ± 0.4 vs. 2.3 ± 0.5 mm2, left 1.5 ± 0.4 vs. 1.8 ± 0.4 mm2; both p < 0.05). There was no correlation between the right or left VN-CSA and age, the Hoehn & Yahr stage, disease duration, the motor part of the Unified Parkinson's Disease Rating Scale score, the Montreal Cognitive Assessment score, or the Non-motor Symptoms Questionnaire, and Scale for Parkinson's disease score including its gastrointestinal domain. Conclusions: These findings provide evidencethat atrophy of the VNs in PD patients can be detected in-vivo by HRUS.