Sinusitis refers to inflammation of the sinus cavities, which are moist, hollow spaces in the bones of the skull. There are four pairs of sinuses:
- Frontal sinuses
- Maxillary sinuses
- Ethmoid sinuses
- Sphenoid sinuses (not shown in illustration)
If the opening from a sinus cavity becomes plugged, the flow of mucus is blocked and pressure builds up, causing pain and inflammation.
Update Date 7/30/2012
Updated by: Seth Schwartz, MD, MPH, Otolaryngologist, Virginia Mason Medical Center, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.