Lots can go wrong with sinuses. For one thing, you might have an extra one! Apparently about 10 percent of the population has extra empty headspace thanks to random genetic variations. There's only a certain amount of room in the head, so an extra sinus has to squeeze in there with the others, meaning the transition space, or ostium, of each of your sinuses will be smaller. The smaller your ostia, the worse for you. When those transition spaces get blocked up, the trouble starts.
And with or without an extra sinus you might just have small, narrow openings regardless. In any case, it's not as though these ostia are major throughways in anybody's head. They're tiny, and they get plugged up with unfortunate ease when the tissues in there are swollen by colds or allergies. The results are less than charming — pressure and headaches, nasal discharge, coughs, loss of smell, blocked ears and sometimes even bloody noses [source: Jacobs]. Headaches are particularly associated with sinus problems because of the pressure build-up in these little skull pockets when the movement of air and fluids through them is blocked.
All of these symptoms are related to sinus inflammation that can prevent mucus from draining into the nasal cavity. When those canals get clogged for too long and put pressure on the middle ear, you might experience ancillary problems like tinnitus, better known as "super annoying ear ringing." In some cases, long-term sinus problems and those nasty nosebleeds can be signs of a number of more serious problems — so if your sinus trouble just won't go away or if you have a fever, extreme fatigue or other symptoms, see your doctor.