4 Important cells in FESS

1.Bulla ethmoidalis -
the biggest and constant anterior ethmoid air cells, The ethmoid bulla lies above the infundibulum. It is suspended laterally from the medial orbital wall and can be seen following removal of the uncinate process. The crescent-shaped space formed between the bulla ethmoidalis and the uncinate process is known as the hiatus semilunaris inferioris. The constant landmark for surgery in FESS

2.Agger nasi cell-
The agger nasi cell derives its name from the Latin that means "nasal knoll". It is the first cell to pneumatize in the new-born. Radiologically, the cell of the Agger Nasi can be identified by coronal CT scan, and can be differentiated from the ethmoid sinus by the degree of pneumatization (the ethmoid is more pneumatized).

The surgical importance of the cell is in its anatomical relation with the adjacent structures. The ceiling of agger nasi forms the floor of the frontal sinus. The frontal recess is behind the posteromedial wall of the cell of the agger nasi. Agger nasi generally grows laterally towards the lacrimal groove, when this does not occur, it can cause a narrowing of the frontal recess and obstruct the drainage of the frontal sinus. Similarly, if the agger nasi cell is excessively pneumatized it can cause obstruction of the frontal sinus ostium and can produce frontal sinusitis.

The lacrimal bones are located close to the lateral surface of agger nasi. Dehiscence of the lacrimal bone can cause ocular symptoms like the epiphoria.

3.Onodi cells
aka sphenoethmoidal air cell is defined as an ethmoidal air cell that lies posteriorly, and sometimes, superiorly to the sphenoidal sinus. As a result of its location the optic nerve, and less commonly, the internal carotid artery, are very closely related with as little a 0.03mm (median 0.08mm) of bone seperating them

Potential damage to the optic nerve and ICA occurs when attempts to enter the sphenoid sinus endoscopically by passing through what is thought to be the the posterior most ethmoidal air cells is instead an Onodi cell.

Additionally, isolated mucocoeles of Onodi cells, squameous cell carcinoma and sinusitis have all been reported, leading to early optic nerve involvement.

4.Haller's cells
are thought to arise from the anterior ethmoid sinus and project in a variable manner into the inferomedial aspect of the orbital floor, opposite the natural ostium for the maxillary sinus. They can be an incidental finding, or when enlarged they can predispose to chronic inflammatory disease of the maxillary and frontal sinuses by narrowing the infundibulum.