The paranasal sinuses are the air filled spaces in the bones of the skull which open into the nose. One pair lies in the cheeks and another in the forehead. There are also a variable number of sinuses between the eyes and the nose. Sinusitis is the infection of these spaces.
Chronic sinusitis is relatively uncommon nowadays.
Acute sinusitis comes on following a cold . If acute sinusitis fails to clear up completely, it may develop into chronic sinusitis. Alternatively chronic sinusitis may develop without any preceding illness. In both cases the development of infection follows blockage of the opening from the involved sinus into the nose. Infection may spread to the sinuses in the cheek from an abscess on the root of a tooth.