The danger zone on the face is a little triangle from the corners of the mouth up to the bridge of the nose. The reason it has such an epic name is because due to its venous drainage (from the facial veins and pterygoid plexus) there’s the possibility of infection traveling from that area into the cavernous sinus.
The cavernous sinuses (there’s one on each side) is an area posterior to the maxillary sinuses and lateral to the pituitary. It receives blood from the superior and inferior ophthalmic veins, superficial cortical veins and the basilar plexus. The blood then drains into the petrosal sinuses (you guessed it, there’s a superior and inferior one of those too) and then those drain into the internal jugular vein.
The thing about the cavernous sinuses a whole lot of important stuff passes through it.
- CN III (occulomotor)
- CN IV (trochlear)
- CN V1 (ophthalmic branch of trigeminal)
- CN V2 (maxillary branch of trigeminal)
- CN VI (abducens)
- Internal carotid (and the sympathetic fibres on the carotid)
This means that if you are so unfortunate as to have infection tract back into it, there can be some nasty consequences like meningitis and cavernous sinus thrombosis which will generally present as problems involving those nerves.
The abducens and carotid are more medial and thought to be more bathed in the warm loving venous drainage meaning these are generally the first to show signs of a problem a-brewin’.