The maxillary sinuses are one of the four paired sets of the paranasal sinuses and the first to develop. In the second month of fetal life, an invagination forms in the lateral wall of the nasal fossa in the middle meatus (1). By the third to fourth months of fetal life, the sinus develops into a pouch and extends into the maxillary bone. At birth, it remains little more than a small sac, no more than 8 mm in length anteriorposteriorly (1, 2). Over time, these air-filled pyramid-shaped cavities extend further laterally and inferiorly as the maxilla becomes more pneumatized.
