While sinus infection is generally not life-threatening, complications of sinusitis can happen especially when the infection is left untreated. The complications of sinusitis include:
Eye infection and abscess
Infections of the sinusitis can spread to the eyes. In the early stages, the eyelids may become swollen. As the infection in the eye becomes worse, the eye itself becomes swollen and painful. Damage to the structures of the eye can result in vision problems such as double vision or blindness.
Blood clot in the cavernous sinus
Untreated sinusitis may lead to blood clots in the cavernous sinus (an important venous system at the base of the brain). The blood clot can restrict the flow of blood from the brain and can allow the bacteria to be spread through the bloodstream. Injury to the tissues of the brain and eyes can result.
Brain infection – meningitis and brain abscess
Infection of the sinuses may spread to the meninges – the membranes surrounding your brain. The classic symptoms include high fever, headache and neck stiffness and altered neurological function.
Further spread of bacteria can lead to the formation of brain abscesses – an accumulation of pus and breakdown products from infection. The swelling and pressure of the brain tissue can cause neurological deficits and coma.
Bone infection – osteomyelitis
The bacterial infection from the sinuses may spread to the surrounding bone especially the bone of the forehead. This can lead to persistent headache, fever, swelling of the bone and discharge of pus through the skin.