The maxillary sinus is one of the four paranasal sinuses. The Maxillary sinus is the largest of the paranasal sinuses. The two maxillary sinuses are located below the cheeks, above the teeth and on the sides of the nose. The maxillary sinuses are shaped like a pyramid and each contain three cavities which point sideways, inwards, and downwards The sinuses are tiny air-filled holes found in the bones of the face which reduce skull weight, produce mucus, and affect the tone quality of a person's voice. The maxillary sinus drains into the nose through a hole called the ostia. When the ostia becomes clogged sinusitis can occur. The ostia of the maxillary sinus often clog because the ostia are located near the top of the maxillary sinus causing drainage to be difficult. Maxillary sinusitis or an infection of the maxillary sinus can have the following symptoms: Fever Pain or pressure in face near the cheek bones Toothache Runny nose Sinusitis is the most common of maxillary sinus illnesses and is usually treated with prescription antibiotics. .