Normative Values of Evans’ Index and Cranial Dimensions on Brain CT Scans: Age- and Sex-Related Variations in a Southeastern Nigerian Hospital Population

Why It Matters

Region‑specific EI norms enable more accurate diagnosis of ventricular enlargement in sub‑Saharan patients, improving clinical decision‑making and research comparability.

Key Takeaways

• Study analyzed 676 normal cranial CT scans.
• Median Evans’ Index 0.28, 95% range 0.22‑0.32.
• EI increases markedly with age, strongest correlation (ρ=0.746).
• Females show higher EI; males larger cranial diameter.
• Age‑sex norms refine ventriculomegaly thresholds in Africa.

Pulse Analysis

Evans’ Index remains a cornerstone metric for assessing ventricular size on CT and MRI, especially in settings where advanced volumetric software is unavailable. In sub‑Saharan Africa, clinicians have long relied on reference ranges derived from Western populations, risking misinterpretation of normal age‑related changes. By providing the first large‑scale, population‑specific dataset from southeastern Nigeria, the study fills a critical gap, offering clinicians locally relevant benchmarks that reflect regional anatomical variations.

The analysis of 676 scans revealed a median EI of 0.28, comfortably within the traditional 0.30 cutoff for ventriculomegaly, yet it highlighted pronounced demographic trends. EI increased from 0.24 in children to 0.30 in those over 81, and females consistently showed higher EI values than males, while males possessed larger internal cranial diameters. These patterns mirror known brain atrophy trajectories but quantify them for an African cohort, allowing radiologists to distinguish pathological enlargement from normal aging more confidently.

Practically, these age‑ and sex‑adjusted norms can refine diagnostic pathways for conditions such as normal‑pressure hydrocephalus, Alzheimer’s disease, and traumatic brain injury, where ventricular size informs treatment decisions. Researchers can also leverage the data to calibrate neuroimaging studies across diverse populations, enhancing the external validity of findings. As imaging technology proliferates across the continent, integrating such localized reference standards will be essential for equitable, evidence‑based neurological care.