Transformation of the shape of the ethmoid bone during the course of life.

The ethmoid bone undergoes significant changes in the course of life. The critical period is the time from 9 to 35 years of age. The changes in its shape depend upon the intensity of pneumatization of the ethmoid labyrinth and frontal sinus. If pneumatization of the labyrinth is excessive, the ethmoidal cells are not covered by the frontal bone. On the contrary, they are incorporated in the inferior floor of the anterior cranial fossa, resulting in a possible risk of penetration during surgical ethmoidectomy.