Cavernous Sinus
This is a weird and mythical part of the head. It’s basically a bit where lots of little veins come together in a bony cavity to share stories and sing campfire songs. Kidding. Basically the reason it’s so important is that lots of things run through the cavernous sinus, and should the cavernous sinus get infected or thrombosed, it will put pressure on all these structures and cause problems. There’s one on each side of your face, and you find them behind the top of your nose, a few centimetres back.
Things that run through the cavernous sinus can be remembered by the handy mnemonic O TOM CAT. It should be written out like this:
(Yep, I made this on GIMP. At least it’s not Paint!)
And here’s what they stand for:
Oculomotor nerve
Trochlear nerve
Opthalmic branch of the trigeminal nerve
Maxillary branch of the trigeminal nerve
internal Carotid artery
Abducens nerve
Trochlear nerve (the T’s cross over so they’re actually the same…)
If there is trauma in the danger area of the face 
(aka danger triangle of face), infection can spread up the facial vein to the cavernous sinus. It can go up the facial vein because the facial vein is a vein of the head and neck and therefore doesn’t have valves. Exciting I know. So then you get infection in the cavernous sinus.
If someone has thrombophlebitis in the facial vein, a bit can break off and get stuck in the cavernous sinus (as it’s just lots of little veins), causing cavernous sinus thrombosis.
The pituitary gland sits between the two cavernous sinuses, so if it’s enlarged it can put pressure on the cavernous sinus. Any other tumours in the area will do the same thing.
Any of these can result in the broadly named cavernous sinus syndrome. It causes a wide variety of problems, such as nerve palsies, haemorrhages and headaches. It is a medical emergecy and needs treatment STAT.
