Patients are placed under general anesthesia and intubated with endotracheal tubes. Immediately after general anesthesia, both nasal cavities are packed with neuropatties soaked with Otrivin (xylometazolin 0.05%). The patients' heads are elevated 15 degrees up. The image guided system is set up and each nasal cavity is examined with a 0 degree endoscope. A 10 cm merocel is cut into a third of its normal size and inserted to the back of the nasopharynx, to prevent blood from flowing into the oropharynx and larynx. An artery forceps is clipped onto the merocel string to prevent dislodgement of the merocel into the larynx or oropharynx. FESS is performed using the technique described by Messerklinger15 and with a microdebrider when deemed necessary. The extent of the operation depends on the severity of the disease seen on the pre-operative CT scan of the paranasal sinus.