Analysis of Cranial Base Suture Fusion Patterns

It is known from both anatomic and radiographic studies that the majority of cranial sutures begin fusing in early adulthood and are fused by late adulthood. However, most of the studies focus on the cranial vault rather than the cranial base. Most clinicians treating patients with craniosynostosis are interpreting the behavior of cranial sutures on CT imaging. Therefore, the purpose of this study was to further clarify the radiographic appearance of cranial base sutures over the natural human life span.

Thirty CT scans of the head and face were reviewed for each decade starting at 1 year of life up to age 90. Scans were evaluated for the appearance of the occipitomastoid, petrosoocciptial, sphenosquamous, sphenopetrosal, frontosphenoidal, sphenozygomatic, petrososquamosal, frontoethmoidal, sphenoethmoidal and sphenoccipital sutures. Sutures were categorized as obliterated, present with fusion, present without fusion and unable to visualize.

The majority of cranial base sutures are visible up through the eighth decade, although evidence of ossification across the suture starts as early as the second decade. Some sutures such as the occipitomastoid appeared > 90% open even as late as the ninth decade. Other sutures such as the sphenosquamosal and frontozygomatic are mostly fused by that age.

Cranial base sutures appear to behave radiographically similar, to the cranial vault sutures in that they largely remain visible throughout adulthood but show varying amounts of ossification. There are some cranial base sutures which appear to remain open throughout life although the significance of this has yet to be determined.