Differential age-, gender-, and side-dependency of vagus, spinal accessory, and phrenic nerve calibers detected with precise ultrasonography measures.

INTRODUCTION: The standard ultrasonographic measurement tools (trace, ellipse) of cross-sectional areas (CSAs) of very small nerves typically yield rough measures in full square millimeters. METHODS: In 70 volunteers, the elliptically shaped CSAs of mid-cervical vagus, accessory, and phrenic nerves were estimated with three methods: 2 on-board tools (area tracing, ellipse fitting) and an off-line calculation of the CSA after on-board measuring of its long-axis and short-axis diameters both displayed with 1-2 digits following the decimal point. RESULTS: CSA measures of all mid-cervical nerves obtained with the precise approach were smaller than the two standard measures (each P < 0.001). Larger CSA of right compared to left vagus nerve was detected with all methods. However, decrease of accessory and phrenic nerve CSAs with increasing age and larger size of vagus nerve CSA in women vs. men were evident only with precise measures. DISCUSSION: Small nerve CSA should preferably be estimated with precise measures. Muscle Nerve 59:486-491, 2019.

Atrophy of the Vagus Nerve in Parkinson's Disease Revealed by High-Resolution Ultrasonography.

Background: The vagus nerve has been suggested to represent one major route of disease progression in Parkinson's disease (PD). Here, we examined whether patients with idiopathic PD exhibit an atrophy of the vagus nerve in comparison to age-matched controls. Methods: In this cross-sectional study, performed between July 2017 and January 2018, we measured the caliber (cross-sectional area) of the mid-cervical vagus, accessory and phrenic nerves in 20 patients with PD (disease duration: 10.1 ± 7.4 years) and 61 (including 20 age-matched) controls using high-resolution ultrasonography. Ultrasonography and assessments of autonomic function were performed by blinded raters. Results: Mean vagus nerve calibers were lower in patients with PD compared to age-matched controls (right: 0.64 ± 0.17 vs. 1.04 ± 0.20; left: 0.69 ± 0.18 vs. 0.87 ± 0.15 mm2; p < 0.001) while accessory and phrenic nerve calibers did not differ. In controls, age correlated negatively with calibers of the accessory and the phrenic nerve (each p ≤ 0.001), and trended to correlate with vagus nerve caliber (p = 0.023). In patients with PD and age-matched controls combined, the summed caliber of the right and left vagus nerves correlated with the burden of autonomic symptoms on the PD Non-Motor Symptoms Questionnaire (r = -0.46; p = 0.003). Moreover, the caliber of the right but not of the left vagus nerve correlated with the parasympathetic domain of heart rate variability (r = 0.58; p = 0.001). Conclusions: PD is associated with a bilateral atrophy of the vagus nerve but not of the spinal accessory or the phrenic nerves. Our findings suggest that viscero-afferent and viscero-efferent vagal fibers are predominantly affected in PD.