Sinusitis
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.

Review Date:
7/25/2007
Reviewd By:
James L. Demetroulakos, M.D., F.A.C.S., Department of Otolaryngology, North Shore Medical Center, Salem, MA. Clinical Instructor in Otology and Laryngology, Harvard Medical School. Review provided by VeriMed Healthcare Network.