Inflammation of one or more of the paranasal sinuses. The sinuses are cavities in the skull connected with the nose, situated in the upper jaw, the forehead and behind the eye sockets. Their function is not precisely known. Theory suggests that they form while the skull is growing to prevent it from becoming too heavy. The sinuses have the same mucous membranes as the nose, which also swell if the patient has a cold, and produce a great deal of mucus. The most important cause of sinusitis is a nasal cold spreading to the sinuses, generally more likely if breathing through the nose is restricted. This is also the case if the nasal septum is displaced by a tumour or nasal polyps (protrusions of the mucous membrane). Sinusitis is a regular occurrence in cases of hay fever and chronic bronchitis, which cause swelling of the nasal mucous membrane. This in its turn can close the small opening from the sinuses to the nose, thus trapping any bacteria which may be there, and providing ideal conditions for them to multiply. Therefore, to prevent or cure sinusitis the openings from the sinuses to the nose should be kept as clear as possible. One of the symptoms of sinusitis is a blocked nose and the production of unpleasant greenish-yellow nasal mucus. Headache, an oppressive feeling around the eyes or swollen eyelids and toothache can occur as a result of inflammation in the forehead cavities, the cavities behind the eye sockets and the upper jaw cavities respectively. As well as these localized symptoms there may be generalized symptoms such as fever, tiredness and a general lack of well-being. If sinusitis is not correctly treated it can lead to chronic sinusitis, in which the symptoms are less serious, but wearisome in the long run; one symptom, for example, is not headache, but an oppressive sensation in the head leading to difficulties in thinking, and reduced activity. Sinusitis can lead to a number of serious complications. Inflammation can spread to adjacent areas, such as the bone of the skull, immediately in front of the sinuses. This is difficult to treat, because antibiotics cannot readily reach bone. Inflammation can also spread to the eye sockets and damage the nerves of the eyes, or to the cerebral membranes, causing meningitis. It is usually quite clear from the symptoms that the patient is suffering from sinusitis. To be completely sure of the diagnosis the family doctor or an ENT specialist can perform a supplementary examination of the inside of the nose, using an instrument (speculum) to hold the cavity open. The rear area of the interior of the nose can be inspected by means of a small mirror held at the back of the throat. A head X-ray also gives a clear indication of the presence of sinusitis. In treating sinusitis it is necessary to ensure that swelling of the mucous membrane of the nose and the sinuses is reduced, so that mucus and pus can be removed via the natural apertures. Reduction of swelling is helped by inhaling hot water vapour or salt solution. Nasal drops can also be used, but not for more than 10 days in succession, to avoid damage to the mucous membrane. It is also wise to avoid great differences in temperature, because they affect the mucous membrane of the nose and sinuses considerably. Aspirin can be used to ease the pain. A doctor should be consulted if the symptoms persist for more than a week, when the inflammation could be so serious that antibiotics are needed to cure it. If sinusitis is caused by other conditions (allergies or nasal polyps) these must be treated if the sinusitis is to be fully cured. If treatment is unsuccessful and the sinusitis threatens to become chronic then rinsing of the cavities can be attempted. The cavity in the upper jaw responds particularly well to this treatment. A needle is inserted into the cavity via the jaw and the jaw cavity is rinsed with liquid, possibly containing antibiotics. If sinusitis persists, then an operation can be performed to make an artificial opening in the relevant cavity. This technique releases the mucus freely and prevents recurrence of the problem.