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.
Review Date 4/13/2020
Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.