Morphometric evaluation of the Evans index in healthy North Indian adults: establishing normative MRI-based reference...

The Evans index (EI) is a practical radiological tool used to assess ventricular size; however, normative reference values remain insufficiently defined across diverse populations. This study aimed to establish normative EI values in a healthy North Indian adult population and to investigate age- and sex-related variations in ventricular morphometry.

A cross-sectional magnetic resonance imaging (MRI)-based study was conducted on 142 neurologically healthy North Indian adults (79 females and 63 males; age range: 18-72 years). Axial T2-weighted images acquired on a 1.5 Tesla MRI system were analysed to measure the frontal horn width (FHW) and the transverse inner diameter of the skull (TIDS). The EI was calculated as the ratio of FHW to TIDS. Statistical analyses were performed using SPSS version 29.0. Welch's t-tests were applied to assess sex differences, Spearman's correlation was used to examine associations between cranial measurements and age, and binary logistic regression was employed to identify predictors of biological sex.

The mean age of the participants was 37.4 years. The overall average measurements were FHW = 31.5 mm, TIDS = 122.4 mm, and EI = 0.257. Males exhibited significantly higher mean EI values than females (0.265 vs 0.251; p < 0.001). Correlation analysis revealed a strong positive association between FHW and EI (rho = 0.866; p < 0.001). Logistic regression analysis identified FHW as the strongest predictor of sex (OR: 1.82, p < 0.001). The model demonstrated a sensitivity of 0.746, a specificity of 0.861, and an AUC of 0.81.

This study establishes normative EI values for healthy North Indian adults and demonstrates significant sex differences in cranial morphometric parameters. FHW and EI are useful predictors of biological sex, with potential implications for clinical neuroimaging and anthropometric assessments.