Biomedical Engineering Reference
In-Depth Information
MCA
Middle Cerebral Artery
MIP
Maximum Intensity Projection
MRA
Magnetic Resonance Angiography
NA
Not Applicable
PCA
Posterior Cerebral Artery
PCoA
Posterior Communicating Artery
PDF
Probability Density Function
SAH
Subarachnoid hemorrhage
SD
Standard Deviation
5.1
Introduction
5.1.1
Brain Aneurysms
Brain aneurysms are pathological dilatations of cerebral arteries. These dilata-
tions consist in a progressive enlargement and deformation of the vessel wall
produced by blood flow pressure. Brain aneurysms tend to occur at or near arte-
rial bifurcations, mostly at the Circle of Willis, the vascular system that irrigates
the basis of the brain.
The Circle of Willis is made up of several vascular segments (Fig. 5.1). The
precommunicating segments (A1, A2) of the left and right Anterior Cerebral Ar-
teries (ACA) and the Anterior Communicating Artery (ACoA) form the anterior
part of the circle. The postcommunicating segments (P1, P2) of the left and right
Posterior Cerebral Arteries (PCA) with the Posterior Communicating Arteries
(PCoA) form the posterior part of the circle. The left and right PCoAs emerge
from the left and right Internal Carotid Arteries (ICA). The Basilar Artery (BA)
and the Middle Cerebral Arteries (MCA), complete the description of the Circle
of Willis.
Brain aneurysms are classified into saccular and non-saccular types accord-
ing to their shape (Fig. 5.2). Non-saccular aneurysms include atherosclerotic,
fusiform, traumatic, and mycotic types. Saccular, or berry, aneurysms typically
arise at a bifurcation or along turns of the parent vessel, or they point in the
direction in which the blood flow would proceed if the turn were not present.
Brain aneurysms are named according to the artery or segment of origin. For
example, anterior communicating aneurysms are located at the ACoA, and
