Was planning to see classmates at upcoming 20th reunion. Now I am hearing my best friend has cavernous sinus aneurysm. What is that?

Type brain aneurysm. The cavernous sinus consists of veins, the carotid artery, and nerves. It can be affected by various disease processes including infections, inflammation, aneurysms, and tumors. Aneurysms usually arise from the internal carotid artery as it passes through the sinus. Aneurysms are dangerous because they may rupture and therefore should be treated using endovascular techniques.