An Aneurysm is a weak abnormal spot on a blood vessel wall that causes a budging shape. As the size increases so to do the risk it rupturing, which may result in uncontrolled bleeding and death. Aneurysms can occur in any blood vessel, including the heart. They are particularly lethal in the brain.
The nanovirus causes a fatal brain aneurysm in its victims. (SGA: "Hot Zone", "The Seer")
The pressure in humans from the Flagisallus' Echolocation can cause the development of an aneurysm. This resulted in the death of Sergeant Bale in 2006. (SGA: "Echoes")
The Sleep parasite gorges on its victims, affecting the surrounding cranial tissue, which eventually results in a lethal aneurysm. (SG1: "Morpheus")
Bryce Ferguson developed an aneurysm over a period of years due to shrapnel lodged against an inter-cranial artery in his head. (SG1: "Stronghold")