Carotid siphon morphology: Is it associated with posterior communicating aneurysms?

Effect of Siphon Morphology on the Risk of C7 Segment Aneurysm Formation : A Case-control CFD Study

PURPOSE

Tortuosity of the internal carotid artery (ICA) is associated with intracranial aneurysms (IAs). The siphon is the most curved segment of the ICA, but its morphology has controversial effects on IAs. This study aimed to explore the morphometric features of the siphon and the potential hemodynamic mechanisms that may affect C7 aneurysm formation.

METHODS

In this study 32 patients with C7 aneurysms diagnosed at Xiangya Hospital between 2019 and 2021 and 32 control subjects were enrolled after propensity score matching. Computed tomography angiography (CTA) images were acquired to measure morphologic features, and then, by combining clinical data, simplified carotid siphon models were constructed, and computational fluid dynamics (CFD) analysis was performed.

RESULTS

The presence of C7 aneurysms was associated with the height of the C4-C6 curved arteries (odds ratio [OR] 0.028, 95% confidence interval [CI] 0.003-0.201; P < 0.001). The heights of the C4-C6 curved arteries in the aneurysm group were significantly shorter than those in the control group. The CFD analysis revealed that shorter C4-C6 bends led to greater blood velocity and pressure in the C7 segment arteries.

CONCLUSION

A shorter C4-C6 bend was associated with distal C7 aneurysm formation, and an elaborate hemodynamic mechanism may underlie this association.

Three-Dimensional Morphometric Analysis of Anterior Cerebral Circulation Aneurysms

This article assesses the association between anterior circulation morphometry and the presence of intracranial aneurysm using three-dimensional rotational angiography (3DRA). A retrospective analysis at a Peruvian academic medical center between December 2018 and February 2020 identified 206 patients with unruptured intracranial aneurysms and matched controls who underwent 3DRA. Angiographic images were obtained per standard of care, and measurements of the vasculature were performed using 3DRA vascular automated software. A total of 163 aneurysms and 43 control angiograms were evaluated. Women represented 82.5% of the cases and the mean age was 55.9 years (standard deviation ± 14.2). In multivariate analysis, five specific features were found to be statistically significant predictors for presence of an anterior circulation aneurysm: female sex (odds ratio [OR] = 2.71; p  = 0.048), C-shape of the middle cerebral artery (MCA) (OR = 2.73; p  = 0.018), distal internal carotid artery (ICA) diameter (OR = 3.42; p  = 0.012), ICA bifurcation angle (OR = 1.02; p  = 0.036), and length of the carotid siphon (OR = 1.08; p  = 0.047). Features detected on 3DRA suggest morphological characteristics of the ICA and MCA may be predictive for intracranial aneurysm. Our findings build from prior reports by demonstrating five specific patient and imaging features associated with anterior circulation aneurysms. While 3DRA is the standard of care in many settings, medical centers with resource limitations may not have access to this technique. The demographic and morphological features identified in our study may have correlates that if detected on contrast computed tomography or magnetic resonance imaging studies, may be used to help screen for a higher level of care in select patients.

Geometric variations associated with posterior communicating artery aneurysms

BACKGROUND

Hemodynamic stress, conditioned by the morphology of the surrounding vasculature, plays an important role in aneurysm formation. Our goal was to identify image-based location-specific parameters that are associated with posterior communicating artery (PCoA) aneurysms.

METHODS

Three-dimensional morphological parameters obtained from CT angiography or digital subtraction angiography from 187 patients with unilateral PCoA aneurysms, diagnosed at the Brigham and Women's Hospital and Massachusetts General Hospital between 1990 and 2016, were evaluated. In order to control for genetic and clinical risk factors, we chose the contralateral unaffected PCoA as a control group. We examined diameters and angles of the surrounding parent and daughter vessels. Univariable and multivariable statistical analyses were performed to determine statistical significance. Sensitivity analyses with small aneurysms (≤5 mm) only and an unmatched analysis of 432 PCoA aneurysms and 197 control patients without PCoA aneurysms were also performed.

RESULTS

In a multivariable conditional logistic regression model we showed that smaller diameter size ratio (OR 1.45×10^-5, 95% CI 1.12×10^-7 to 1.88×10^-3) and larger daughter-daughter angle (OR 1.04, 95% CI 1.02 to 1.07) were significantly associated with PCoA aneurysm presence after correcting for other variables. In subgroup analyses of small aneurysms (≤5 mm) and in an unmatched analysis the significance and direction of these results were preserved.

CONCLUSIONS

Larger daughter-daughter angles and smaller diameter size ratio are significantly associated with the presence of PCoA aneurysms. These simple parameters can be utilized to guide the risk assessment for the formation of PCoA aneurysms in high risk patients.

Potential Risks and Limited Indications of the Supraorbital Keyhole Approach for Clipping Internal Carotid Artery Aneurysms

Background

Internal carotid artery (ICA) aneurysm may be a good target for supraorbital keyhole clipping. We discuss the surgical indications and risks of keyhole clipping for ICA aneurysms based on long-term clinical and radiologic results.

Methods

This was a retrospective analysis of 51 patients (aged 35–75 years, mean 62 years) with ICA aneurysms (mean 5.8 ± 1.8 mm) who underwent clipping via the supraorbital keyhole approach between 2005 and 2017. Neurologic and cognitive functions were examined by several methods, including the modified Rankin Scale and Mini-Mental Status Examination. The state of clipping was assessed 1 year and then every few years after the operation.

Results

Complete clipping was confirmed in 45 patients (88.2%), dog-ear remnants behind the clip persisted in 4 patients, and wrapping was performed in 2 patients. Mean duration of postoperative hospitalization was 3.4 ± 6.9 days. The mean clinical follow-up period was 6.6 ± 3.2 years. The overall mortality was 0, and overall morbidity (modified Rankin Scale score ≥2 or Mini-Mental Status Examination <24) was 3.9%. Completely clipped aneurysms did not show any recurrence during the mean follow-up period of 6.3 ± 3.1 years, but the 2 (3.9%) aneurysms with neck remnants showed regrowth.

Conclusions

The risk of neck remnant behind the clip blade is a drawback of supraorbital keyhole clipping. The surgical indication requires preoperative simulation and careful checking of the clip blade state is essential.