Surgery should be considered if more than four courses of antibiotics are needed over a one year period to treat sinus infections. Only 20 percent of people are surgical candidates—they have anatomical obstruction of the sinuses. In such cases, nasal endoscopy performed in the office by an ear, nose, throat specialist and a sinus CT scan may reveal an anatomical cause for sinus obstruction. This blockage can be treated successfully with a minimally invasive procedure known as endoscopic sinus surgery. During this procedure, a narrow endoscope is passed through the nostrils to remove the areas of blockage and enlarge the sinus drainage passages. Sinus surgery has about an 80 percent success rate and generally reduces the frequency and severity of symptoms. New technologies, including the use of surgical navigational systems that guide the surgeon through the sinuses much like a GPS system guides missiles to their target, provide the tools for safe and effective sinus surgery.