Vagus nerve cross-sectional area decreases in Parkinson's disease

Morphological alterations of the vagus nerve (VN) in Parkinson's disease (PD) are discussed controversially. Several studies reported no difference in VN cross-sectional area (CSA) in PD patients in nerve ultrasound, others found a reduced CSA interpreted as atrophy of the VN and involvement of the dorsal nucleus of VN.

In a prospective comparative cross-sectional study, CSA of the VN bilaterally and the right ulnar nerve, clinical PD scales, non-motor symptoms and autonomic tests were compared between 49 PD patients and 24 healthy controls. Nerve ultrasound was performed by two independent investigators, patients and controls were compared at Bonferroni corrected p < 0.025 using results of both investigators and averaged results. Blinding included CSA measurements and PD scores, but not PD diagnosis.

Bilateral averaged VN CSA was significantly lower in PD patients than in controls (Right VN PD mean 2.70 mm² SD 0.69, controls 3.30 mm² SD 0.49, p < 0.001. Left VN PD mean 2.45 mm² SD 0.57, controls 2.77 mm² SD 0.46, p = 0.012). No difference was found in the ulnar nerve. There was a weak negative correlation between the right VN CSA and the Unified Parkinson Disease Rating Scale (-0.08 mm² per 10 points). The area under the receiver operating characteristic curve for the right VN was 0.78 (p < 0.001).

The present results support the hypothesis of atrophy of the VN in PD. Reduction of VN CSA is a weak marker of disease progression. Nerve ultrasound of the VN might represent a supplementary method in diagnosis of PD.