Edema is another word for a type of swelling. With edema, you actually have an increase of pressure and that pressure can cause pain. For instance, if you have edema in the sinus cavities, that edema can actually push against the wall of the skull indirectly through the sinus cavities. If it does, you'll actually feel pressure in that area. Many times doctors are able to tell with their patients where the pressure is just by palpating, or pushing, that area and trying to find out where it occurs.
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