aneurysm
Meaning of aneurysm: A weakened patch of artery wall stretched outward by the pressure inside it, usually silent until the day it is not.
Definition of aneurysm
An aneurysm is a bulge in the wall of an artery, formed where the wall has weakened and been pushed outward by the pressure of blood inside. The bulge tends to enlarge over time, because a wider vessel carries more wall tension at the same pressure. Most cause no symptoms at all while they remain intact, and the danger lies in tearing or bursting.
Where do they form?
| Site | What it is called | How it usually comes to light |
|---|---|---|
| Aorta in the abdomen | Abdominal aortic aneurysm | Seen on a scan or ultrasound arranged for another reason |
| Aorta in the chest | Thoracic aortic aneurysm | Seen on chest imaging, or sought because of an inherited condition |
| Arteries at the base of the brain | Berry or saccular aneurysm | Found incidentally, or at the moment it bleeds |
| Behind the knee | Popliteal aneurysm | Felt as a pulsating swelling, or when it clots off |
The aorta is the commonest site because it carries the highest pressure of any vessel in the body. Brain aneurysms are the next most discussed, and they behave differently: they are small, they sit in a confined space, and a bleed from one floods the fluid space around the brain rather than the tissue itself.
Why does a bulge keep growing?
Physics works against it. Tension in the wall of a tube rises with the width of that tube at the same internal pressure, so a segment that has already stretched is under more strain than the healthy wall beside it, and it stretches further. The weakening that starts the process comes from several directions: the wear of fatty deposits, smoking, sustained high blood pressure, inherited disorders of connective tissue such as Marfan syndrome, injury, and occasionally infection seeded into the wall. Family history counts, and close relatives of someone with an aortic aneurysm carry a higher chance of having one themselves.
What happens if one bursts?
Bleeding is internal and rapid, and rupture is immediately life-threatening. A torn abdominal aortic aneurysm produces sudden severe pain in the abdomen or back together with collapse. A ruptured brain aneurysm produces a headache that reaches its full intensity within seconds, often with neck stiffness, vomiting and loss of consciousness, and how instantly it peaks is what marks it out from an ordinary bad headache. Because an intact aneurysm gives no warning, most are found by accident, and once one is known its diameter is measured on repeat imaging or on an angiogram so that growth can be followed, since the risk of rupture rises as the bulge enlarges.
Also known as
Used in a sentence
An abdominal aortic aneurysm was noted incidentally on the abdominal scan.
Good to know
An intact aneurysm usually produces no symptoms, so most are discovered on imaging arranged for something else, and a false aneurysm, which is a contained leak sitting outside the vessel wall rather than a stretched wall, is a different lesion despite the shared name.
Word origin
Where “aneurysm” comes from
Aneurysm comes from the Greek aneurysma, a widening, built from ana, meaning up or throughout, and eurys, meaning wide.