by Mark S. Schubert, M.D., PhD.
The sinuses are cavities in the skull that connect to the nose. They are in the forehead, cheeks, between the eyes, and in the center of the skull directly behind the bridge of the nose. In a sense, the sinus cavities can be considered a continuation of the nose into the skull. The purposes of the sinuses included air humidification, and to hollow out the skull so it isn’t terrible heavy (as it would be if it were solid bone).
The sinuses are lined by the same skin that lines the inside of the nose, called mucosa. The mucosa has fine microscopic hairs on it (cilia) that orchestrate a beating motion to propel mucus, which is made by the mucosa, from the sinus cavities out into the nose. Mucus then moves down the back of the throat to be swallowed. The mucus serves as a line of defense against infection. A normal adult will form about a quart of such secretions a day, making the trip from the sinuses and nose down the throat.
In some individuals, the mucosa can become chronically inflamed. One of the most common forms of chronic sinus disease is called hypertrophic sinusitis. Hypertrophic sinusitis is a disorder of the sinus mucosa. In these patients, the mucosa is chronically inflamed, often due to allergies. Once this inflammation gets started, it is hard to stop, for reasons that are poorly understood; there may be a genetic component. Allergic inflammation causes death of the cilia, as well as an increased production of mucus. These two events lead to pooling of secretions in the sinus cavities. Additionally, allergic inflammation causes the sinus mucus to grow abnormally into masses of tissue in these individuals. The sinus cavities may become filled with this abnormal tissue which is chronically inflamed. Why chronic allergic inflammation stimulates this sinus membrane to grow into large masses is unknown. Obstruction of the outflow of mucus from the sinuses then occurs, followed by infection with bacteria causing further damage to the mucosa. More inflammation then occurs, then more growth of the mucosa, worsening the situation. Polyps are inflamed sinus mucosal masses.
Surgery is often required to remove the disease mucosa, and antibiotics are usually required to kill associated bacteria as well. Often it is necessary to use a course of oral corticosteroids, such as prednisone, to suppress the ongoing allergic inflammation and slow the disease process. Long-term treatment and prevention of hypertrophic sinusitis often requires the identification and control of allergies, so that recurrence of this chronic sinus disease can be diminished.
Posted in: Sinus Disease