Computed Tomography-Aided Morphometric Analysis of the Foramen Magnum for Neurosurgical Insights: A Pilot Study in the Pakistani Population.

BACKGROUND

The foramen magnum (FM) is a critical structure at the craniovertebral junction (CVJ), influencing surgical access, radiological evaluation, and forensic sex estimation. Although international reference values exist, computed tomography (CT) based FM morphometry remains underreported in the Pakistani population. This study provides population-specific high-resolution computed tomography (HRCT) measurements, evaluates gender and age-related variation, and classifies FM shape using the Martin and Saller index.

MATERIALS AND

METHODS

A retrospective analysis of 166 adult HRCT scans (78 males, 88 females; age: 18-87 years) was conducted using 1.0-mm axial bone-window images on the Vitrea workstation. Measurements included anteroposterior diameter (APD), transverse diameter (TD), FM index (FMI), and FM area (FMA). FM shape was categorized into narrow (≤81.9%), medium (82-85.9%), and large (≥86%). Data were analyzed using descriptive statistics, ANOVA, and Pearson's correlation.

RESULTS

Males exhibited consistently larger FM dimensions than females across all age decades. TD, FMA, and FMI showed similar gender-based dimorphism. The most frequent FM shape in both genders was narrow, with 52.3% incidence in females and 41% in males ( p  = 0.345). FM shape varied significantly across age groups ( p  = 0.018). Two-way ANOVA demonstrated significant age effects on APD ( p  = 0.023), gender effects on TD ( p  < 0.001), and FMI ( p  = 0.016). APD and TD strongly correlated with FMA ( r  = 0.848 and r  = 0.835), while FMI negatively correlated with FMA( r  = -0.353).

CONCLUSION

This study establishes HRCT-based FM reference values for a Pakistani adult subpopulation, demonstrating gender dimorphism, age-related variation in APD and FM indices, and a predominance of the narrow FM shape. These findings support neurosurgical planning, radiological interpretation, and forensic applications within the Pakistani setting.