Meningitis, encephalitis, and brain abscess are rare complications of sinus infection. However, they can be life threatening and need to be treated immediately. Each of these infections is caused by complications of sinus disease and begins with symptoms that include headaches, fever, stiff neck, behavioral changes, and loss of concentration. The carotid artery, which carries the blood supply to the brain, runs along the outside wall of the sphenoid sinus; and the veins that drain the brain of deoxygenated blood end in the cavernous sinus, which is located behind the sphenoid sinus. As a result of the close proximity of these important vascular structures to the sphenoid sinus and the fact that this sinus is under the brain, a sphenoid sinus infection can spread to the brain quite easily. The frontal sinus sits in front of the brain, and the roof of the ethmoid sinus is the floor of the brain; therefore, infection in these areas can also spread to the brain. Furthermore, the blood vessels that supply the nose are connected to the blood vessels that supply the brain, so an infection of the nose can spread to the brain. Although rare, a brain abscess can form from an infection in any of these areas or a thrombosis of the cavernous sinus can occur as a result of a sphenoid sinus infection.
The number one cause of meningitis is sinus infection. Infection of the nose and sinuses are especially dangerous to the brain because an infection can travel upstream through the veins in the nose, which, unlike most veins, do not have valves. Any microfracture in the bone separating the sinuses from the brain can allow infection to travel to the brain or the surrounding tissues, leading to meningitis. Any small tear in the brain’s covering (the dura) can lead to encephalitis. Furthermore, if the infection travels through the venous drainage into the brain, a brain abscess can occur.