If you've ever had a cold that just wouldn't go away, chances are it was sinusitis — an inflammation of the paranasal sinuses, the cavities within the bones that surround the nose. The sinuses are lined with a thin membrane that produces mucus, which is normally swept along by hair cells and drains through small openings into the nasal cavity. Sinusitis (also called rhino-sinusitis) starts when this drainage system becomes blocked, usually from swelling due to inflammation ca