Vagus Nerve Cross-Sectional Area in Patients With Parkinson's Disease-An Ultrasound Case-Control Study

Abstract

Background: Vagal parasympathetic neurons are prone to degeneration in Parkinson's disease (PD). High-resolution ultrasound can precisely estimate the cross-sectional (CSA) area of peripheral nerves. Here, we tested the hypothesis that vagus CSA is reduced in PD. Methods: We included 56 healthy controls (HCs) and 63 patients with PD. Using a high-end ultrasound system equipped with a high-frequency transducer, five images were obtained of each nerve. The hypoechoic neuronal tissue was delineated offline with dedicated software and the CSA extracted. Results: In the initial PD vs. HC comparison, no statistically significant differences were observed in mean left vagus CSA (HC: 1.97 mm², PD: 1.89 mm², P = 0.36) nor in mean right vagus CSA (HC: 2.37 mm², PD: 2.23 mm², P = 0.17). The right vagus CSA was significantly larger than the left vagus CSA in both groups (P < 0.0001). Females were overrepresented in the HC group and presented with generally smaller vagus CSAs. Consequently, sex-adjusted CSA was significantly smaller for the right vagus nerve of the PD group (P = 0.041), but not for the left. Conclusion: A small but significant reduction in sex-adjusted right vagus CSA was observed in patients with PD. The left vagus CSA was not significantly reduced in patients with PD. Ultrasound may not be a suitable method to detecting vagal axonal loss in individual patients.

Keywords: cross-sectional area; parasympathetic; parkinson's disease; ultrasound; vagus nerve.

Figure 1

Representative ultrasound image of the vagus nerve. (A) The vagus nerve (white arrow) of a patient with PD. (B) Delineation of the same vagus nerve following the hyperechoic epineurium. IJV, internal jugular vein; CCA, common carotid artery; CSA, cross-sectional area.

Figure 2

Left and right vagus nerve cross-sectional area (CSA) is presented for patients with Parkinson's disease (PD, black circles) and healthy controls (HC, white circles). Mean and standard deviation is depicted with black error bars.