To better understand sinusitis, it helps to understand the anatomy of the nasal passages and sinuses.

The sinuses are open cavities inside the bones of the face. Sinuses are located between the eyes, under the cheekbones, and in the forehead. They are connected by small channels that run between the sinuses. Normally, the sinuses do not contain fluid. There are four main sinus cavities.

The four main sinuses include:

• Frontal sinuses:
• Located behind the eyebrows
• Ethmoid sinuses:
• Deep sinuses are located behind the eyes and over the nose
• Maxillary sinuses:
• Two sinuses are on either side of the nose, behind the cheekbones
• Sphenoid sinus:
• Located deep in the face, at the base of the brain