Figure 3.

Strains and suture patency. (A) Cross-sectional depiction of the sagittal suture depicting the paired parietal bones (P). The dura mater is the tough membrane that adheres to the inner surface of the cranial vault, which separates it from the brain. The pericranium is located apically. The growth of the cranial vault is regulated by a harmonious balance of proliferating and differentiating cells occurring within the suture (blue). This growth takes place in synchrony with an expanding brain (black arrows). Therefore, we can describe this behavior by plotting the effect of normal expanding brain and its effect on the suture as a stress-strain curve. (B) Conversely, in craniosynostosis, this balance is disturbed by external forces as in utero constraints during pregnancy (green arrows), poor brain expansion (vertical black arrows) and/or abnormal signal transduction within the suture (red shade). Generally, reduced brain growth has the effect of reducing quasi-static tensile strain across the calvarial suture as shown in the stress-strain graph.