|Taken from Wikipedia|
Why is this region considered dangerous?
It's because infections within this region can lead to infections of the brain (rarely). Why? The blood supply within this triangular area communicates with the cavernous sinus found at the bottom of the brain. This anatomic structure is a major source of venous drainage of the brain.
If the cavernous sinus gets inflamed/infected due to a rip-roaring pimple of the upper lip, it could lead to multiple facial abnormalities due to injury of the numerous cranial nerves that go through it including:
• Inability to move the eyeballs (CN3, 4, 6)
• Numbness, pain of the skin over the forehead and cheeks (CNV1, V2)
• Loss of pupillary constriction (CN3)
• Visual loss/changes (CN1)
The cavernous sinus could also become thrombosed.
|Cavernous Sinus shown by red arrow. Taken from Sonoworld.|
From there, the infection can spread to the rest of the brain and potentially can even lead to death if not treated promptly and aggressively.
Of course, tiny infections like a small pimple or a small laceration due to biting a lip is not going to cause problems.
However, rapidly progressive major infections of the skin with abscess formation do need to be treated cautiously. Typically, such patients are hospitalized on IV antibiotics until definite and significant improvement can be seen at which time patients can be discharged home on oral antibiotics.
At which point a "minor" infection becomes "major" requiring hospitalization is a judgement call.