Sinuses are air-filled spaces in the bones of the face.  Scientists do not really knows why we have sinuses.  Some possible explanations are; to make the skull lighter, to act as crumple zones in case of trauma, to help resonate the voice or to  kill germs that move through the nose.  They are connected to the inside of the nose through small openings which can sometimes become blocked and cause symptoms.

Endoscopic Sinus Surgery is the name given to the operation to treat sinus problems, which have not improved with sprays and antibiotics.  The operation is performed while the patient is  asleep and requires no cuts on the face.  It is performed using a small telescope (endoscope) and other instruments that fit inside the nostrils.  Sometimes balloons are used to dilate and open the drainage channels.

Serious complications are extremely rare but can include damage to the eye or a leak of brain fluid through the nose.