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 +/- 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.