TOPLINE

Patients with Parkinson's disease (PD) had significantly reduced cross-sectional area (CSA) of the vagus nerve on ultrasonography compared with controls in a meta-analysis of 12 studies.

METHODOLOGY

• A meta-analysis of 12 studies published up to January 2026 and involving 1091 participants (541 with PD and 550 control individuals without PD) was conducted to evaluate vagus nerve CSA measured by ultrasonography.
• Studies utilized various ultrasound devices with probe frequencies ranging from 4 to 18 MHz, and measured the vagus nerve at different anatomical landmarks including the thyroid gland level and carotid artery bifurcation.

TAKEAWAY

• A significant reduction in right vagus nerve CSA in PD patients compared with control individuals (1.97 vs 2.21 mm²), with differences of 0.24 mm² (95% CI, −0.38 to −0.09).
• Patients with PD also had smaller mean left vagus nerve cross-sectional areas than controls (1.70 vs 1.89 mm²; mean difference, −0.19 mm²; 95% CI, −0.31 to −0.07).
• No consistent correlation was found between vagus nerve CSA and autonomic dysfunction.

IN PRACTICE

"This meta-analysis shows a difference at the group level, but the inter-individual variation in CSA is large," the authors wrote, noting "the clinical utility for diagnosis, that is, correctly classifying single patients, is limited despite statistical significance." 

"Clinicians should not use vagus nerve ultrasound as a PD biomarker or diagnostic test in current practice," they added .

SOURCE

The study was led by Laura C.J. Sijben, Maastricht University Medical Center, Maastricht, Netherlands. It was published online on July 15 in the Journal of Neurology.

LIMITATIONS

The limitations included substantial heterogeneity across studies, most studies did not differentiate between brain-first and body-first PD phenotypes, and large inter-individual variation in CSA limits.

DISCLOSURES

No specific funding was reported for this meta-analysis. The authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.