Ultrasonography of the Vagus Nerve in the Diagnosis of Parkinson’s Disease

Abstract

Background. It is currently impossible to diagnose Parkinson’s disease (PD) in the premotor phase even though at the time of motor symptom onset the number of already degenerated dopaminergic substantia nigra neurons is considerable. Degeneration of the dorsal nucleus of the vagus nerve (VN) has been reported early in the disease course, and it could lead to impaired function of the VN, resulting in certain nonmotor symptoms of PD. Therefore, we raised a hypothesis that the loss of VN neurons could result in a smaller diameter of the VN among PD patients. Methods. 20 PD patients and 20 age- and gender-matched individuals without any neurodegenerative disease were enrolled in a pilot study. The diameters of the right and left VNs were measured using ultrasonography, their average was calculated, and the narrower VN diameter was noted separately. Results. No difference was found between the PD and control groups neither in the average VN diameter (mean 1.17; 95% confidence interval (CI) 1.10–1.24 vs. 1.13; 1.07–1.18, mm; p=0.353) nor in the narrower VN diameter (mean 1.11; 95% confidence interval (CI) 1.02–1.20 vs. 1.07; 1.02–1.13, mm; p=0.421). The narrower VN diameter and the average VN diameter were not able to distinguish between PD patients and controls (area under curve (AUC) = 0.588, 95% CI = 0.408–0.767, and p=0.344; and AUC = 0.578, 95% CI = 0.396–0.759, and p=0.402). Conclusions. To conclude, no differences were found in VN diameter between the PD and control groups. Therefore, our data do not support the hypothesis that PD could be associated with a smaller diameter of the VN.

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

“…Our findings confirm the findings of two studies which also found no reduction in CSA of the vagus nerve in PD patients [19,20]. We were unable to replicate the reduction in CSA as reported by earlier studies [16][17][18].…”

“…Moreover, this method potentially identifies persons at risk even before a clinical diagnosis of PD can be confirmed. It is however important to note that two studies using B-mode ultrasound could not confirm that the CSA of the vagus nerve was decreased in PD [19, 20].…”

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

“…Cardiac sympathetic neurons are particularly vulnerable in PD (28) and may also contribute to slight vagal atrophy. However, if vagal atrophy is mainly caused by sympathetic and parasympathetic (DMV) axonal loss, the reduction in CSA is probably very small and could explain why three studies failed to show vagal atrophy in PD (20)(21)(22). Additionally, the vagus nerve shows frequent branching (up to 29%) (29).…”

“…Four studies found significant atrophy of both left and right vagus nerves in patients with PD (16)(17)(18)(19). In contrast, three studies reported no difference between patients with PD and healthy controls (HCs) (20)(21)(22). Thus, whether ultrasound can detect vagal neuronal loss in patients with PD remains unresolved.…”

Noninvasive vagus nerve stimulation in Parkinson’s disease: current status and future prospects

“…There is some evidence that the structural integrity of the vagus nerve, measured using high-resolution ultrasound, may be altered in PD. Some studies have found that both left and right vagus nerves are significantly smaller in patients relative to age-matched controls [45][46][47], while others have shown a comparable size of the vagus nerve between patients and controls [48][49][50][51].…”