Cerebral lateral ventricular asymmetry: a meta-analysis and meta-regression of volumetric MRI studies

The right and left lateral ventricles are symmetrically positioned and typically mirror each other by size and shape. Therefore, they often serve as a primary reference point on magnetic resonance imaging (MRI) scans. However, volumetric ventricular asymmetry is a frequent radiological finding. In this study, we aimed to assess whether one ventricle is, on average, larger than the other.

We carried out a systematic search for articles published by August 2024 in three large electronic databases. The articles included reported left and right lateral ventricle volumes from MRI in healthy individuals. As a subsidiary analysis, we performed meta-regressions to examine total ventricular volume, age, and sex as potential moderators of ventricular asymmetry.

A total of 58 studies (8,642 subjects) were considered eligible and included in the meta-analysis. In nearly all studies, an asymmetry in the lateral ventricles was found; in 47 of them, the left ventricle was the larger. The pooled effect size was considered significant (p < 0.0001), as the left lateral ventricle was 6.5% larger than the right lateral ventricle. The meta-regression analyses revealed that the degree of asymmetry is correlated with ventricular volume, but not with age and sex.

This meta-analysis confirms that the left lateral ventricle is typically larger than the right. Given this asymmetry's links to neurological and psychiatric conditions, future research should focus on defining the limits of healthy asymmetry and clarifying the sources of heterogeneity to enhance diagnostic and clinical applications.