Establishing Normative Cranial Landmarks for Posterior Fossa Assessment in an African Population: A Diagnostic Tool for Posterior Fossa Lesions

Résumé

Background: Accurate evaluation of posterior fossa structures is critical for distinguishing brainstem from cerebellar and fourth ventricular lesions. This study aimed to establish normative values for the ratio between the distance from the dorsum sellae to the roof of the fourth ventricle (DS–V4) and the distance from the dorsum sellae to the torcula (DS–T) in an African population, and to evaluate its diagnostic utility. Methods: In this cross-sectional study, 420 individuals underwent cranial MRI. Distances from the dorsum sellae to the roof of the fourth ventricle (DS–V4) and to the torcula (DS–T) were measured on midsagittal T1-weighted images, and the DS–V4/DS–T ratio was calculated. Results were compared with existing literature to assess differences in these ratios relative to non-African cohorts. Results: Mean DS–V4/DS–T ratios were 0.568 (95% CI, 0.543–0.594) in males and 0.570 (95% CI, 0.561–0.579) in females, with no significant sex difference. Age-related trends reflected expected cranial growth patterns. Ratios in this West African cohort appeared slightly higher than values reported in some European series. Conclusion: A higher DS–V4/DS–T ratio may suggest brainstem or clival lesions, whereas a lower ratio may indicate cerebellar or posterior fossa lesions. The DS–V4/DS–T ratio represents a practical diagnostic marker for posterior fossa assessment and may be particularly valuable in low-resource settings where access to advanced imaging is limited.