CURVATURE EFFECT ON HEMODYNAMIC CONDITIONS AT THE INNER BEND OF THE CAROTID SIPHON AND ITS RELATION TO ANEURYSM FORMATION

Alexandra Lauric PhD, James Hippelheuser BS, Mina G. Safain MD, and Adel M. Malek MD PhD

Cerebrovascular and Endovascular Division

Department of Neurosurgery

Tufts Medical Center and Tufts University School of Medicine

Boston, MA 02111

Motivation:Carotid Siphon Aneurysms

Intracranial Aneurysms

• Aneurysm formation on the inner aspect of vascular bends has not been thoroughly addressed.

• We evaluated • The effect of vessel curvature on sidewall aneurysm formation

on the internal carotid artery (ICA) • The hemodynamics on aneurysm formation along the inner

carotid siphon.

Method for Curvature Analysis

• Catheter 3D-rotational angiographic volumes of 130 patients• 72 aneurysms – 10 in the inner curve of the carotid siphon• 58 controls

• The centerline of the ICA was determined and curvature along ICA was automatically computed.

• The radius of curvature and the peak curvature of the siphon bend were evaluated in 3D.

ICA Focal Curvature

ICA Focal Curvature• Intracranial ICA was measured 50 mm

caudal from the ICA bifurcation. • Distal ICA was measured from the

carotid siphon to the ICA bifurcation. • The peak curvature of the intracranial

ICA (red arrow) doesn’t always coincide with the peak curvature of the distal ICA (black arrow).

ICA Curvature Statistics

Group Feature Aneurysm Non-aneurysm p

Aneurysm (n=74) Cintra_mean 0.15±0.016 0.14±0.015 <.001

vs. Cintra_max 0.40±0.053 0.37±0.057 .002

Healthy (n=58) Cdistal_mean 0.18±0.031 0.16±0.027 <.001

Cdistal_max 0.34±0.068 0.28±0.052 <.001

• Aneurysmal ICAs have significantly higher global and focal curvature on the whole intracranial ICA, but also on the distal (dural) portion of the ICA.

ICA Curvature Statistics

• ICA curvature of aneurysmal and non-aneurysmal samples (age between 53 and 68 years old). The black arrows point to the position of the peak curvature of the distal ICA.

A. Male ICA harboring an aneurysm on the ophthalmic segment

B. Control male

C. Female ICA harboring a carotid superior hypophyseal aneurysm

D. Control female

• Local curvature features were evaluated in 10 patients with aneurysms on the inner wall of the carotid siphon. Peak focal curvature of the siphon The radius of curvature of the siphon

Inner Carotid Siphon Aneurysms

Carotid Siphon Analysis• Peak focal siphon curvature was significantly higher in

aneurysm bearing ICAs compared to controls • 0.36 ± 0.045 vs. 0.30 ± 0.048 mm-1, p=0.003

• No difference in global radius of curvature• 3.71 ± 0.64 vs. 3.93 ± 0.70 mm, p=0.36

Conclusions

• Aneurysm formation is associated with tight curvature globally, but also locally, on the hosting segments.

• In the carotid siphon, high peak focal curvature is correlated with aneurysm presence.

References

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