Sinusitis is an inflammation of the maxillary sinus (air cavity in the maxillary bone). Inflammation causes the accumulation of pathological secretions in the naso-maxillary area which triggers disorders that include pain, altered sensitivity, headache, nasal discharge of mucus, and fever. The causes of sinusitis can be inflammatory, dental, traumatic, polyposis of the maxillary sinus, or neoformations. Sinusitis is diagnosed clinically and radiologically by computerized tomography. The modern treatment of these inflammatory forms involves the collaboration of the maxillo-facial surgeon with the ENT. The minimally invasive surgical approach is called FESS: Functional Endoscopic Sinus Surgery.