Glossary of Terms




Radiological imaging of blood vessels after the injection of a contrast dye.

Angiogram (arteriogram)

This is the "gold standard" for diagnostic evaluation, according to an American Heart Association statement as it is the most comprehensive, specific, and sensitive. It is, however, a more expensive and extensive procedure.

Patient Procedure: You will need to go the pre-admission clinic for blood work, a medical history discussion and a physical exam. The evening before the procedure, you will not be allowed to eat or drink after midnight. When you report for the procedure, you will be asked to change into a hospital gown, remove all metallic and memory-coated devices such as watches, dentures, contact lenses, glasses etc. (as discussed previously).

First, an intravenous (IV) tube will be inserted into your arm to administer medication and fluid for your comfort during and after the procedure. The nurse will shave a small area on your groin where the neuroradiologist will inject a local anesthetic to numb the area. When the area is numb, the neuroradiologist will insert a catheter in the artery and then inject the dye, which travels through your blood vessels and heart to your brain.

When the dye is injected, you may feel some burining sensation in your face and a warm sensation in your head. Fluoroscopy pictures are then taken and reviewed by the neuroradiologist. The doctor then removes the catheter and applies pressure to the insertion area for ca. 15 minutes. You are kept flat for 6-8 hours, after which you can resume normal activity.

According to the AHA statement, CT (standard computed tomography) with or without contrast agents is considered too imprecise for adequate diagnosis of brain aneurysms. However, CTA (computer tomographic angiography) may pinpoint aneurysms as small as 2 to 3 mm. Magnetic resonance Angiography (MRA) is useful for screening, especially for aneurysms 3 to 5 mm or more in diameter, and is the most heavily used test.

Keep in mind that 5mm is thought to be the critical threshold size for aneurysm rupture risk. However, MRAs are expensive ($500-$1,000) so there is currently only support for screening people with a significant demonstrated risk. Moreover, the MRI machines distributed throughout the U.S. vary in quality based on their prices, translating to varied degrees of detection accuracy making nation-wide effective screening difficult.

If you choose to be screened, ensure that a minimum threshold machine of xxx accuracy, xxx specificity is used. The gold standard, however, for diagnostic evaluation of intracranial aneurysms is intra-arterial catheter angiography. Although these new technologies have made screening techniques more accurate and less invasive, much research is still needed to make screening more cost-effective so that more people can be screened more routinely.


A complication of hypertension, an increase in blood pressure over time causes artery walls to thicken in response which makes them less flexible. This does not tend to happen in the brain so much, but near the heart which the pressure is greatest.

Arteriovenous Malformation - AVM

At least partly hereditary, this malformation results in arteries leading directly to veins, without going through the capillary bed (smaller distributary blood vessels). The veins have to dilate or enlarge in order to handle the pressure of the blood coming directly from the arteries rather than the smaller capillary tributaries. This weakens the walls of the veins, making them susceptible to rupture.


This is a blood vessel that takes blood from the heart towards other parts of the body. Veins are the vessels that collect the blood once it has fed the body tissues a supply of oxygen and bring it back to the heart and lungs to get pumped out once again. Aneurysms usually are located in arteries because they experience higher blood pressures, with blood recently pumped through the heart.


This term refers to the lack of perceivable symptoms, as, for example, many persons who have an aneurysm do not feel any symptoms and are therefore asymptomatic.


This term refers to the build-up of plaque and cholesterol within the walls of the arteries over time. As these deposits enlarge, they constrict the lumen (the tunnel inside the artery through which the blood flows) causing it to narrow while at the same time reducing the capacity for the artery to stretch.



Aneurysms are often located at the site where an artery splits into two smaller arteries, termed a bifurcation, as the blood pressure is naturally greater on this junction.



This term describes anything pertaining to the circulatory system within the cerebrum, that is, more simply, the blood vessels in the head.

CT - Computer Tomography

A painless, safe test, the CT examines cross-sections of the brain through x-ray and an interpretive computer. As it is only captures a flat 2-D slice of the brain (like a piece of paper), usually several scans are done to provide the doctor with layers of anatomical information at different depths.

CTA - Computer Tomography Angiography

This augments the CT scan with a contrast dye, injected into a vein which allows for 3-D imaging, highlighting the blood vessels in the brain.


Embolus (plural: emboli)

A piece of debris, such as part of a thrombus or blood clot broken off the artery wall, that travels in the blood stream and can block smaller arteries.


Within the blood vessel, Endovascular therapy uses the natural access to the brain through the bloodstream via the arteries to diagnose and treat brain aneurysms. The goal of the treatment is to safely seal off the aneurysm and stop further bleeding or possible rebleeding.



A fistula is an abnormal connection between an organ, vessel, or intestine and another structure.

Fusiform Aneurysm

An aneurysm which is spindle-shaped and lacks a distinct neck.



A mass of usually clotted blood that forms as the result of a broken blood vessel. Because the brain is in an enclosed space, a hematoma can increase the pressure on the brain tissue, vessels, and spinal fluid contained in the brain.


Bleeding, as, for example, when an aneurysm ruptures, a hemorrhage or bleeding may occur.


This term describes an increase in blood pressure that can cause tiny arterioles in the brain to burst. The resulting bleeding in the brain can then cause compression on the surrounding tissue, leading to more burst vessels in a positive feedback mechanism.



Disease or deficits, as, for example, deficits in brain function following a ruptured aneurysm or resulting from complications following treatment.


Death, as in, for example, the mortality or death rate resulting from a ruptured aneurysm.

MRA - Magnetic Resonance Angiography

This combines the MRI procedure with a contrast agent. A solution called a contrast agent aneurysm, which typically has few or no side effects, is injected into a vein (routine shot). The dye clarifies the picture, allowing the radiologist to construct a 3-D image and better distinguish the structure of the aneurysm.

MRI - Magnetic Resonance Imaging

This non-invasive test allows your doctor to see many internal organs including the brain without surgery, x-rays or pain. The magnetic resonance machine creates a magnetic field, sends radio waves through your body, and then measures the response with a computer creating an image or picture.

Patient Procedure: You will be asked to change into a hospital gown and lie on a special table, which will slide you under the MRI machine. While undergoing the exam, you will hear clicking noises as the machine scans you. You will be asked to remain as still as possible during the exam which generally lasts no longer than an hour.


Saccular Aneurysm

The type of aneurysm which is sac-like in shape and has a well-defined neck.


This term technically refers to the death of brain tissue due to an interrupted blood supply and subsequent lack of oxygen. This dead brain tissue is referred to as an "infarct". There are two ways a stroke can occur: ischemic or hemorrhagic. Ischemic stroke refers to the blockage of an artery by usually by a blood clot combined perhaps with a constriction of the artery (see atherosclerosis). The type of stroke caused by a ruptured aneurysm is hemorrhagic, where bleeding within the brain causes compression and damage to the tissue.

Subarachnoid Hemorrhage (SAH)

An event of rupture or bleeding into the space around the brain, as, from an aneurysm.



A clot in the cardiovascular system formed from consitituents of blood.