Abstract
BACKGROUND AND PURPOSE
Intracranial aneurysm is a devastating disease of complex etiology that is not fully understood. The purpose of this study was to assess the implications of carotid siphon anatomy for the formation and development of intracranial aneurysms.
MATERIALS AND METHODS
Between January 2007 and May 2015, lateral view digital subtraction angiographic images of 692 consecutive patients with intracranial aneurysms treated in our department of interventional neuroradiology were reviewed and had their angles measured. Data on the location, presentation, and size of the lesions were collected and evaluated by multivariate analysis in relation to the measured angles.
RESULTS
Of 692 aneurysms, 225 (32.51%) ruptured and 467 (67.49%) unruptured, 218 (31.50%) were in the carotid siphon and 474 (68.50%) were distal to the siphon, and the mean aneurysm size was 7.99 ± 6.95 mm. Multivariate analysis showed an association between angles of >15.40° and rupture (P = .005), postsiphon location (P = .034), and aneurysm size of >1.001 mm (P = .015). Multivariate analysis also showed that every 1-year increase in patient age produced an increase of 1.002 mm in aneurysm size (P = .015).
CONCLUSIONS
There was a significant independent direct relation of greater anterior knee angle with intracranial aneurysms located distal to the carotid siphon, larger aneurysms, and greater risk of rupture. These findings may be associated with the hemodynamic interactions of blood flow and the curvature of the carotid siphon.
Intracranial aneurysms affect approximately 6%–10% of the world population. Fortunately, only 0.05% of patients progress to rupture, but they face a devastating consequence, subarachnoid hemorrhage, with mortality rates ranging from 56% to 80%.1,2
Several factors are related to the formation, development, and rupture of intracranial aneurysms. Among these, the hemodynamic interactions of blood flow and vessel wall have received special attention in recent years. The balance between hemodynamic stress secondary to blood flow in the water hammer pulse and parallel shear stress caused by blood viscosity and friction between blood and the arterial wall appears to be related to the origin and development of aneurysms. That hemodynamic contribution can be exemplified by the preferred location of aneurysms at arterial bifurcations and curvatures.3⇓⇓–6 Thus, the carotid siphon is of particular importance because it is a tortuous vessel segment with sharp bends through which blood enters the anterior cerebral circulation.7⇓–9
The aim of this study was to investigate the morphologic characteristics of the carotid siphon and their possible association with the formation, development, and occurrence of intracranial aneurysms at this site.
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Fellows’ Journal Club
Lateral view DSA images of 692 consecutive patients with intracranial aneurysms treated at the authors’ institution were reviewed and had their angles measured. Data on the location, presentation, and size of the lesions were collected and evaluated by multivariate analysis in relation to the measured angles. Multivariate analysis showed an association between angles of >15.40° and rupture (P = .005), postsiphon location (P = .034), and aneurysm size of >1.001 mm (P = .015). These findings may be associated with the hemodynamic interactions of blood flow and the curvature of the carotid siphon.