**2. Frontal sinus anatomy**

The frontal sinus has a thick strong anterior wall, a thin fragile floor and a posterior wall. Its floor is the roof of the orbit. Its posterior wall forms the anteroinferior portion of the anterior wall of the anterior cranial fossa. Because the superior sagittal sinus lies against the posterior wall of the frontal sinus, it is vulnerable to injury in fracture dislocations of the posterior wall. Fortunately because of the toughness and resiliency of the dura, rupture of the superior sagittal sinus is uncommon, but when it occurs, the patient often dies of uncontrollable hemorrhage [1]. A vertical septum has commonly placed approximately in the center of the frontal sinus. In the case of highly developed orbital ethmoidal cells, the roofs of these cells make up the medial aspect of the frontal sinus floor. The nasofrontal ducts are located on either side of the frontal sinus. The opening of these structures is variable. They usually drain directly into the

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frontal recess, but they also may drain above the ethmoid infundibulum, into it or above the ethmoid bulla.

The frontal sinus is lined with pseudostratified ciliated columnar epithelium. The main source of blood supply to the frontal sinus is a diploic branch of the supraorbital artery [2].The frontal sinus also receives some blood supply from branches of the anterior ethmoidal artery [1].External venous drainage is through the angular and anterior facial veins. The deep drainage is through the foramen of Breschet which is located on the posterior wall of the sinus. This structure is responsible for communication with the subdural venous system in the subarachnoid space [1].
