Aneurysm

An aneurysm is a localized, abnormal, weak spot in the wall of an artery. If an aneurysm grows large the vessel "balloons" until it bursts, causing dangerous bleeding or even death.
Most aneurysms occur in the aorta (the main artery that runs from the heart through the chest and abdomen). Aneurysms also can happen in arteries in the brain, heart, and other parts of the body. If an aneurysm in the brain bursts, it causes a stroke.
They are generally congenital, but often do not risk bursting until the patient is in their teenage years or older.
Aneurysms are very difficult to diagnose and treat. Death can follow within hours of the onset of symptoms. Modern imaging technology has made it possible to spot aneurysms, but the only treatment is to repair the vessel. 
The vessel in question is usually one of the major arteries to a vital organ, often the carotid artery, which means that blood flow to the vital organ cannot be maintained during surgery. As such, patients must be cooled to the point of hibernation, preserving their organs during surgery, until the aneurysm can be repaired. This procedure is very dangerous, but aneurysms are inevitably fatal so the treatment is usually worth the risk.
==On House==
﻿House's infarction that led to his disability was the result of an aneurysm that clotted, blocking the flow of blood to most of the muscle in his right thigh.
In Brave Heart, the patient had an intracranial berry aneurysm, an aneurysm shaped like a sac or berry in one of the blood vessels that feeds the brain.
==As a differential diagnosis==
In Love Hurts, Harvey Park was suffering from strokes, which pointed to a brain aneurysm. They performed an operation to remove it, but he was clean. He finally was diagnosed fulminating osteomyelitis. He needed an operation to fix the jaw.
In Runaways, Collie Rogers was suffering from breathing problems and multiple bleeds, which pointed to a berry aneurysm. After she passed out, an operation was performed to remove it, but she was clean. After the operation she was diagnosed with ascariasis and would only need Mebendazole.
Aneurysm