The sinuses are surrounded by bone and cartilage and lined with a mucous membrane. Sinusitis occurs when the membranes becomes inflamed and painful, which may be a result of a blocked sinus opening.
Chronic sinusitis is often caused by inflammation and blockage due to physical obstruction such as a deviated septum, misformed bone or cartilage structures such as the nasal conchae (turbinates), or blockage by nasal cysts or polyps.
Reviewed By: Sumana Jothi, MD, specialist in laryngology, Assistant Clinical Professor, UCSF Otolaryngology, NCHCS VA, SFVA, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.