Mendosal suture patency beyond infancy: a large-scale computed tomography study in an Asian cohort

Purpose: The mendosal suture, or accessory occipital suture, is thought to obliterate prenatally or neonatally, and its persistence is often misinterpreted as a skull fracture. Although recent studies suggest that it may persist beyond infancy, its prevalence and clinical significance in Asian populations remain unclear. This study aimed to determine the prevalence and characteristics of persistent mendosal sutures in a Thai population aged 1–20 years. Methods: A retrospective review of 1403 cranial computed tomography scans was conducted, with three-dimensional reconstructions evaluated by three blinded investigators. Sutures were classified as completely patent (continuous horizontal line across lambdoid sutures) or partially patent (residual suture with areas of fusion), and intra- and interrater reliability were assessed using intraclass correlation coefficients. Results: The overall prevalence of persistent mendosal sutures was 6.4%, with partial patency (4.8%) more common than complete patency (1.6%); both were observed across all age groups. Intra- and interrater reliability was excellent. Median age differed statistically significantly among groups (P = 0.001): 16 years for partial patency, 8 years for complete patency, and 11 years for no suture. Cephalic index showed a small but statistically significant difference (P = 0.048), although all values remained within normal limits. No statistically significant associations were found with sex, family history of craniofacial anomalies, or other sutural synostoses. Conclusion: The mendosal suture persists into adulthood in 6.4% of Thais, challenging the assumption of consistent early-infancy obliteration. Its presence across all ages, lack of association with pathology, and normal cephalic indices suggest that it is a benign anatomical variant rather than a marker of disease.