Sinusitis, an inflammation of the paranasal sinuses, is brought on by a viral, bacterial, or fungal infection. the most commonly affected paranasal sinuses are the most inferior ones, which are called

The inferior most, or the lowest, sinus cavity is called the maxillary sinus. It is also the largest sinus cavity and it drains into the middle of the nose. The maxillary sinus is located above the upper jaw and is easily visible on x-rays above the premolar and the molar teeth. 
The symptoms of sinusitis include headaches near the sinus and discharge of foul-smelling mucus.