Figure 13: Relevant anatomical variants of the paranasal sinuses prior to FESS.
a) 43-year-old patient with chronic rhinosinusitis and recurrent surgery; complete opacification of the maxillary sinus on both sides. Haller cell (arrow) on the left side causing obstruction of the left ostiomeatal complex along with an ethmoid bulla. The patient underwent cranial surgery (arrowhead) due to meningioma.
b) 19-year-old female patient; ethmoid bulla on the left side. Keros type II Cribriform plate variant.
c) 37-year-old patient prior to surgery. Concha bullosa of the middle turbinate on the right side (x). Left convex deviation of the nasal septum (arrow) with small bony spur. Small Haller cell and opacified ethmoid bulla on the right side.
d) 56-year-old patient with exacerbation of chronic rhinosinusitis after repeated surgery. Small bony spur in the course of the anterior ethmoid artery (arrow). Keros type I cribriform plate variant.