Lecture 13 + 14 - Biomechanics and Mechanobiology of intracranial aneurysms

Question 1

What is the rupture rate and mortality of intracranial aneurysms?

Answer 1

<0.1-1% rupture annually
30-40% of ruptures are fatal

Question 2

Describe the evolution of treatments for intracranial aneurysms? (4)

Answer 2

1 Clip
2 Coil
3 Coil & Stent
4 Flow Diverters

Question 3

What is the true reason for high IA formation risk at bifurcations?

Answer 3

Strong localization of aneurysm-type remodeling to the region of accelerating flow suggests that a combination of high WSS and high gradients in WSS represents a “dangerous” hemodynamic condition that predisposes the apical vessel wall to aneurysm formation.

Question 4

How do clinicians determine which aneurysms to treat?

Answer 4

Geometric / mechanical state (morphology) (more complex more likely to rupture)
Solid mechanics or CFD approach (hard to image to get properties)

Question 5

Which material components of the artery are dominant?

Answer 5

collagen fibres recruited at high pressure only (crimped at low pressure)

elastinous components load bear at low pressure

Question 6

If not pressure, what causes aneurysm formation?

Answer 6

Either very high or very low wall shear stress

Question 7

What mechanism can lead to low wall shear?

Answer 7

Elastin degradation linked to low wall shear stress

collagen remodels to achieve homeostatic stretch during cardiac cycle

collagen growth linked to magnitude of cyclic deformation of cells