Serious complications with sinusitis are rare. In some cases, sinusitis can lead to meningitis or a brain abscess, leading to seizures, coma and even death. Severe sinusitis can also cause infection of the frontal bone leading to osteomyelitis(or infection of bones) of the skull and infection around the eye, leading to inability to move the eye or even blindness. These complications are medical emergencies that require immediate treatment.
Attribution: Straight Talk Foundation