An intracranial aneurysm is a saclike widening of an artery in the brain. Common locations for these aneurysms include arteries in the brain. This document discusses using computer modeling to simulate how increases in blood pressure from activities like exercise or straining relate to mechanical stress and strain within intracranial aneurysms. The modeling is used to compare stress and strain under normal, exercise, and straining blood pressure conditions to better understand rupture risk, though diameter remains the primary clinical measure of risk.

2.  An aneurysm is defined as:
A cardiovascular disease characterized by a saclike
widening of an artery resulting from weakening of the
artery wall
 Intracranial aneurysms(ICA) have a prevalence of 2%-
6.5%
 Common places for ICAs are the cerebral artery, internal
carotid artery, basilar artery, and the anterior
communicating artery
 Cerebral blood pressure is autoregulated
 Currently doctors use diameter as a measure of severity
1. http://wordnetweb.princeton.edu/perl/webwn?s=aneurysm
2. Chien A, Castro MA, Tateshima S, et al. Quantitative hemodynamic analysis of brain aneurysms at different locations. AJNR Am J Neuroradiol. 2009;30:1507‐1512.

3.  Relate acute increases in blood pressure with
mechanical stress and strain values within an
intracranial aneurysm.

4. http://en.wikipedia.org/wiki/File:Circle_of_Willis_en.svg

5.  Einc:
 .65MPa
 12.2MPa
 12.2MPa
 ν=.499
 Shell Elements, thickness=.086mm
 Pressure
 Control-122 mm Hg
 Aerobic exercise-163 mm Hg
 Valsalva-250 mm Hg
 Elastic/Isotropic material
Middle cerebral blood pressure during a Valsalva manouver in the standing position, Frank Pott, et al., J Applied Physiology
Physical exercise increases middle cerebral artery blood flow velocity, Gunnar Hellstrom, Nils Gunnar Wahlgren, Neurosurgery Rev.
The static elastic properties of the arterial wall, D. H. Bergel, J. Physiology

6.  Obtain aneurysm as .dat file and convert to .stl
 Load into IA-FEMes 1.0
 Create block structure
 Mesh seed-> length=.25
 Mesh-> shell elements
 Add ELSETS & BCs
 Export to ABAQUS
 Manually enter pressure values
 Run ABAQUS and complete post processing

8. 14
12
10
8
Mpa
Max VonMises
6
max at 3407
4
2
0
Control Exercise Valsalva
Valsalva

9. Lowering maximum stress
threshold shows greater
detail in values which
further deviate from the
maxima
Regions of high stress
have a strong correlation
with regions of greater
contour
Valsalva

10. 70
60
50
40
Magnitude of
30
20 Disp
10 max at 3407
0
Exercise

12. Max In-Plane Strain
10
8
6
Max in plane stress
4
max at 3407
2
0
Control Exercise Valsalva

13. Risk of intracranial aneurysm rupture varies
greatly from patient to patient. There is not
enough information known to use stress/strain
as an indication for rupture. However, there
tends to be a concentration of stress near areas
of large contour.
Diameter of the aneurysm is likely the
simplest/most effective method of assessing
aneurysm risk of rupture in a clinical setting