Function of the Sinuses

If you don’t know what the sinuses are for, you’re in good company because no one else does, either. Theories that have been advanced include lightening the bones of the skull so that we can move our head easier, providing “crash protection” for the brain, humidifying and filtering the air that we breath, and providing resonance for the voice. The first two of these can never be proved or disproved, and the latter two have been shown not to be true. Recently it has been shown that the sinuses make an enormous amount of a substance called nitric oxide (not to be confused with nitrous oxide, which is “laughing gas”) and this substance diffuses from the sinuses into the air we breath. Nitric oxide has a lot of effects on the lungs and other organs of our body, so perhaps the sinuses may turn out to be “nitric oxide factories”.


Myths About the Sinuses

The sinuses are sort of like El Nino in that they get blamed for a lot of things that they probably have nothing to do with. First, the sinuses produce very little mucous. While it is true that about one quart of mucous is made in the nose every day, most of this is made by cells in the nasal mucosa (the covering of the nose and sinuses), not in the sinus mucosa. Thus, if you have a problem with a runny nose or postnasal drip, you are much more likely to have some sort of rhinits (inflammation of the nose) rather than sinusitis.

The second myth about the sinuses is that they are a common cause of headaches and facial pain. While it is true that a bacterial infection of the sinuses can be painful, most people with headaches have no evidence of bacterial sinusitis. Also, certain signs that are supposed to indicate that you have a “sinus headache” are unfortunately not very reliable. For example, all headaches will get worse if you bend your head over, and many people with tension headaches (or even vascular headaches) will be tender in the area of the pain.

One group of patients that are somewhat perplexing are those whose headaches improve when they use a decongestant tablet or spray. One theory of sinus headaches is that they are “vacuum headaches”. The reasoning behind this is that if the small opening between the nose and a sinus gets blocked, the air that is trapped in the sinus eventually gets absorbed into the body, leaving a partial vacuum which may be painful. Thus, using a decongestant nasal spray or tablet may “unblock” the opening and relieve the headache. While this may indeed occur in some patients, unfortunately I can find very little evidence of sinus blockage in many patients with headaches, usually even those whose report that decongestants help their headaches. At present my working hypothesis is that at least some of these patients may suffer from vascular headaches, and since decongestants are also very strong vasoconstrictors (they shrink swollen blood vessels), it is this effect which is causing the improvement in their headache pain. For more information on headaches and sinus disease, click on the appropriate link on the left.


Diagnosis of Sinusitis

There are a number of well-done studies that have clearly shown that unfortunately, we’re not very good at diagnosing sinusitis. There is no one symptom, or even group of symptoms, that can allow one to say “Yes, this patient has sinusitis.” Similarly, there is no one thing in a patient’s history that is diagnostic, since a lot of the symptoms of sinusitis (nasal obstruction, postnasal drip, fatigue) can be caused by a lot of other illnesses. The two things that may be the most helpful are sinus endoscopy and sinus x-rays. Sinus endoscopy is where a small telescope is used to examine the inside of your nose. Although the telescope can’t look directly into the sinuses, the condition of the mucosa near the sinus openings can give some indication of the condition of the sinuses themselves. Sinus x-rays can be either plain x-rays or CT scans. Although the CT scan is better at picking up subtle sinus disease, it needs to be interpreted with caution, as there is some suggestion it may be too sensitive. For example, anywhere from 25% to 45% of patients without any symptoms of sinus disease may show an abnormality on a sinus CT. Similarly, about 90% of people that simply have a cold will show evidence of sinus disease on a sinus CT. Thus, any abnormal findings need to be interpreted with caution and correlated with clinical evidence of disease.


Treatment of Sinusitis

The optimal treatment of sinusitis is also not as clear as one would like. For acute sinusitis (a single episode of infection that may last from 1 to 3 weeks) certainly an antibiotic is appropriate. Although this is usually prescribed for 10 days, there is some evidence that a shorter course (even as short as 3 days) may be just as effective. One should also keep in mind that 60% to 70% of bacterial sinusitis will clear by itself without resorting to an antibiotic. For recurrent or chronic sinusitis (symptoms recur frequently or are present all of the time) there have been no good studies of appropriate treatments. There is a trend (unfortunate, in my opinion) to treat this with longer and longer courses of antibiotics, but whether this really helps has not been shown scientifically. Steroids (either as a nasal spray or by mouth) are also often prescribed. Again, while there are theoretical reasons these may help, hard evidence is lacking.


Summary

In summary, we don’t know what the sinuses do, it’s hard to tell when they’re truly infected, and most of the treatments used have not been scientifically proven. But---that’s what makes the practice of medicine interesting, and, in the long run, why I think an educated patient will be a happier and hopefully healthier patient.