My son has cavernous sinus thrombosis. what is it, in a nutshell?

Blood Clot: Thrombosis means a condition of having a blood clot somewhere. Cavernous sinus is a "type of vein" found in the brain. An infection that occurs in structures around the cavernous sinus (sinus infection) can cause a blood clot to form. Some veins, arteries and nerves "run through" this area (see diagram). A blood clot can intefere with these structures.