Surgical anatomy of the cerebral arteries in patients with subarachnoid hemorrhage: comparison of computerized tomography angiography and digital subtraction angiography

Geometry and Symmetry of Willis' Circle and Middle Cerebral Artery Aneurysms Development

Background: A relationship between the geometry and symmetry of Willis' circle and intracranial aneurysms was reported for anterior communicating and posterior communicating (PCom) aneurysms. A similar association with the middle cerebral artery (MCA) aneurysms instead appeared weaker. Methods: We reviewed 432 patients from six Italian centers with unilateral MCA aneurysms, analyzing the relationship between the caliber and symmetry of Willis' circle and the presence of ruptured and unruptured presentation. CT-angiograms were evaluated to assess Willis' circle geometrical characteristics and the MCA aneurysm side, dimension and rupture status. Results: The hypoplasia of the first segment of the anterior cerebral artery (A1) was in approximately one-quarter of patients and PCom hypoplasia was in almost 40%. About 9% had a fetal PCom ipsilaterally to the aneurysm. By comparing the aneurysmal and healthy sides, only the PCom hypoplasia appeared significantly higher in the affected side. Finally, the caliber of the internal carotid artery (ICA) and the first segment of MCA (M1) caliber were significantly greater in patients with unruptured aneurysms, and PCom hypoplasia appeared related to the incidence of an ipsilateral MCA aneurysm and its risk of rupture. Conclusions: Although according to these findings asymmetries of Willis' circle are shown to be a risk factor for MCA aneurysm formation and rupture, the indifferent association with ipsilateral or contralateral hypoplasia remains a datum of difficult hemodynamic interpretation, thereby raising the concern that this association may be more casual than causal.

The rupture of an anterior communicating artery aneurysm does not associate with an asymmetry in the A1 or A2 arteries: a retrospective study of radiological features

BACKGROUND AND OBJECTIVES

Although the formation and rupture risk of an anterior communicating artery (ACoA) aneurysm has been the subject of many studies, no previous study has primarily searched for the relationship of the parent and daughter vessels and the impact of their size/diameter ratio on the potential rupture risk of an AcoA aneurysm. The objective of this study is to explore this link and to further analyse the surrounding vasculature of the anterior communicating artery aneurysm.

MATERIALS AND METHODS

We conducted a retrospective analysis of 434 patients: 284 patients with an ACoA aneurysm (121 unruptured and 162 ruptured) and 150 control patients without an ΑCoA aneurysm. Radiological angiography investigations were used to assess the diameter ratios of the parent vessels in addition to ACoA aneurysm morphology parameters.

RESULTS

When comparing the ruptured to the unruptured cases, we observed no significant difference in the parent or daughter vessel diameter ratios. Younger patient age (OR 0.96, p = 0.00) and a higher aneurysm size ratio (OR 1.10, p = 0.02) were of prognostic importance concerning the rupture risk of the aneurysm. The A1 diameter ratio and the A2 diameter were not statistically significant (OR 1.00, p = 0.99, and OR 3.38, p = 0.25 respectively).

CONCLUSIONS

In our study, we focused on asymmetry in the parent and daughter vessels as well as traditional ACoA aneurysm morphological characteristics. We were able to label younger patient age and a greater size ratio as independent prognostic factors for ACoA aneurysm rupture. We were unable to label parent and daughter vessel asymmetry as prognostic factors. To validate our findings, parent and daughter vessel asymmetry should be subjected to future prospective studies.

Successful microsurgical clipping of ruptured fusiform aneurysm of the anterior cerebral artery. Case report and review of the literature

BACKGROUND

Fusiform aneurysms (FA) of the anterior cerebral artery (ACA) are found rarely. The common clinical presentation is a subarachnoid hemorrhage (SAH). Surgery is the main treatment to prevent rebleeding.

CASE DESCRIPTION

The authors present a case report of the ruptured FA of the ACA. The presented case demonstrates the successful microsurgical clipping of the fusiform ACA aneurysm.

CONCLUSION

A1-segment FA can lead to SAH with poor prognosis. The main goal of surgical treatment is to prevent rebleeding. Direct microsurgical clipping is one of the surgical options.

Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells

The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life’s biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.

Aneurysms of the communicating segment of the internal carotid artery with posterior communicating artery agenesis are associated with perforator infarction after embolization

BACKGROUND

While anatomic features associated with the risk of posterior communicating artery (PcoA) occlusion after embolization of aneurysms of the PcoA segment of the internal carotid artery (ICA) are well known, the link between perforator origin and perforator infarction has only been reported following neurosurgical clipping. The aim of this study was to determine the origin of anterior thalamic perforators and correlate it with risk of perforator infarction after embolization of PcoA segment aneurysms.

METHODS

One-hundred-and-ninety consecutive patients treated for PcoA segment aneurysms between 2017 and 2019 were included. PcoA and anterior thalamic perforator origin anatomy was assessed with computed tomography (CT) angiography, digital subtracted angiography, and high-resolution three-dimensional rotational cone-beam CT angiography (CBCT-A) by two independent interventional neuroradiologists. The presence of perforator infarction after embolization was ascertained from the patient's notes and follow-up imaging.

RESULTS

CBCT-A was superior in demonstrating the origin of perforators (P<0.001). The prevalence of perforator origin was estimated at 86% (95% CI 81%-92%) for PcoA, 8% (95% CI 4%-13%) for aneurysm wall, and 5% (95% CI 2%-9%) for ICA. The aneurysm wall origin was exclusively associated with PcoA agenesis, as well as higher risk of perforator infarction after aneurysm coiling compared with other variants (OR=14, 95% CI 2-88, P=0.006).

CONCLUSIONS

Our study suggests that anterior thalamic perforators may arise from aneurysm wall when there is no PcoA. Anatomic association between PcoA agenesis and perforator arising from ICA could underlie such findings, and careful consideration is essential before aneurysm repair to anticipate the risk of thalamic infarction in such cases.

Basilar Apex Aneurysms in the Setting of Carotid Artery Stenosis: Case Series and Angiographic Anatomic Study

Background:

Intracranial aneurysms (IAs) are life-threatening lesions known within the literature to be found incidentally during routine angiographic workup for carotid artery stenosis (CAS). As IAs are associated with vascular shear stress, it is reasonable to expect that altered flow demands within the anterior circulation, such as with CAS, increase compensatory flow demands via the Circle of Willis (COW) and may induce similar stress at the basilar apex.

Objective:

We present a series of nine unruptured basilar apex aneurysms (BAA) with CAS and a comparative radiographic analysis to BAA without CAS.

Methods:

Twenty-three patients with BAA were retrospectively identified using records from 2011 to 2016. CAS by North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria, morphology of BAA, competency of COW, and anatomic relationships within the posterior circulation were examined independently by a neuroradiologist using angiographic imaging.

Results:

Nine (39%) of the twenty-three BAA patients had CAS, with six having stenosis ≥50%. Four (67%) of the patients with ≥50% CAS demonstrated aneurysm flow angles contralateral to the side with highest CAS. Additionally, the angle between the basilar artery (BA) trajectory and aneurysm neck was observed to be smaller in patients with ≥50% CAS (61 vs 74 degrees). No significant differences in COW patency, posterior circulation morphology, and degree of stenosis were observed.

Conclusion:

Changes in the cervical carotid arteries may lead to blood flow alterations in the posterior circulation that increase the propensity for BAA formation. Posterior circulation imaging can be considered in CAS patients to screen for BAA.

Multidetector CT angiography of the Circle of Willis: association of its variants with carotid artery disease and brain ischemia

PURPOSE

(1) to estimate the prevalence of Circle of Willis (CoW) variants in patients undergoing carotid endarterectomy, (2) to correlate these variants to controls and (3) cerebral ischemia depicted by computed tomography (CT).

MATERIALS AND METHODS

After Institutional Review Board approval, data of 544 carotid endarterectomy patients (331 males, mean age 69±8 years) and 196 controls (117 males, mean age 66±11 years) who underwent brain CT and carotid CT angiography (CTA) were retrospectively analysed. Two observers independently classified each CoW segment as normal, hypoplastic (diameter <0.8 mm) or non-visualized. Four groups of CoW variants based on the number of hypoplastic/non-visualized segments were correlated with clinical data (ANOVA, χ² and multivariate logistic regression analysis). Intra- and inter-observer agreement was estimated using Cohen κ statistics.

RESULTS

High prevalence of CoW variants (97%) and compromised CoW (81%) was observed in the study group and significant difference was found in the distribution of CoW variants compared to controls (p<0.001), internal carotid artery (ICA) stenosis being the only independent predictor of CoW morphology (p<0.001). Significant correlation was found between CoW configuration and brain ischemia in the study group (p=0.002). ICA stenosis of ≥90% was associated to higher rate of ipsilateral A1 hypoplasia/non-visualization (p<0.001). Intra- and inter-observer agreement was from substantial to almost perfect (Cohen κ=0.75-1.0).

CONCLUSION

Highly variable CoW morphology was demonstrated in patients undergoing endarterectomy compared to controls. Likely compromised CoW in relation to cerebral ischemia was observed in a large cohort of carotid endarterectomy subjects.

KEY POINTS

• CoW variant distribution significantly differed in the study and control groups (p<0.001). • ICA stenosis was the only independent predictor of CoW morphology (p<0.001). • Severely compromised CoW configuration showed significant association with brain ischemia (p=0.002).

Anterior Communicating Artery Aneurysm Morphology and the Risk of Rupture

BACKGROUND

Recently, with improvements in computed tomography angiography and digital subtraction angiography, the assessment of certain morphologic traits of anterior communicating artery aneurysms (ACoAA) has drawn great attention. The determination of specific factors associated with rupture would provide much-needed guidance for the treatment of unruptured intracranial aneurysms, such as surgical clipping or endovascular coiling. Morphologic factors include, but are not limited to, aneurysm size, number, shape, dome direction, neck/dome ratio, and relationship of the aneurysm to the surrounding vessels. However, the results of previous investigations concerning morphologic parameters have yielded inconsistent results.

METHODS

This review presents and analyzes the literature on the morphology of ACoAAs and risk of rupture.

RESULTS

This literature review reveals that the strongest predictors of ACoAA rupture are size ratio, direction of the dome, and fenestration. These were the only factors that were either unanimously or near unanimously found to be predictive of rupture across multiple studies.

CONCLUSIONS

The size ratio, direction of the dome, and fenestration should be examined most meticulously when deciding when to treat an ACoAA.

Relationship of A1 segment hypoplasia to anterior communicating artery aneurysm morphology and risk factors for aneurysm formation

OBJECTIVE Hypoplasia of the A₁ segment of the anterior cerebral artery is frequently observed in patients with anterior communicating artery (ACoA) aneurysms. The effect of this anatomical variant on ACoA aneurysm morphology is not well understood. METHODS Digital subtraction angiography images were reviewed for 204 patients presenting to the authors' institution with either a ruptured or an unruptured ACoA aneurysm. The ratio of the width of the larger A₁ segment to the smaller A₁ segment was calculated. Patients with an A₁ ratio greater than 2 were categorized as having A₁ segment hypoplasia. The relationship of A₁ segment hypoplasia to both patient and aneurysm characteristics was then assessed. RESULTS Of 204 patients that presented with an ACoA aneurysm, 34 (16.7%) were found to have a hypoplastic A₁. Patients with A₁ segment hypoplasia were less likely to have a history of smoking (44.1% vs 62.9%, p = 0.0410). ACoA aneurysms occurring in the setting of a hypoplastic A₁ were also found to have a larger maximum diameter (mean 7.7 vs 6.0 mm, p = 0.0084). When considered as a continuous variable, increasing A₁ ratio was associated with decreasing aneurysm dome-to-neck ratio (p = 0.0289). There was no significant difference in the prevalence of A₁ segment hypoplasia between ruptured and unruptured aneurysms (18.9% vs 10.7%; p = 0.1605). CONCLUSIONS Our results suggest that a hypoplastic A₁ may affect the morphology of ACoA aneurysms. In addition, the relative lack of traditional risk factors for aneurysm formation in patients with A₁ segment hypoplasia argues for the importance of hemodynamic factors in the formation of ACoA aneurysms in this anatomical setting.

Accuracy of CT angiography in detection of blood supply dominance of posterior cerebral artery in patients with posterior communicating artery aneurysm

BACKGROUND AND PURPOSE

The use of computed tomography angiography (CTA) as the sole vascular imaging study for preoperative planning for clipping of aneurysms is well described in the literature. CTA is widely available, provides quick acquisition, has low morbidity, and low cost. In this study, we describe the accuracy of CTA in determining the blood supply dominance in comparison to standard digital subtraction angiography.

MATERIALS AND METHODS

Sixty-six patients, with both CTAs and angiograms, were reviewed by two independent neuroradiologists. The posterior cerebral artery was determined to have dominant supply from the posterior communicating artery if it was of similar size to the P2 segment and the P1 segment was smaller by approximately 50%. If the posterior communicating artery and P1 segment were the same size, it was considered to have a dual supply. If P1 and P2 segments were the same caliber and the posterior communicating artery was smaller by 50%, it was deemed to have posterior circulation dominance.

RESULTS

Based on the findings of our reviewers, CTA had a sensitivity and specificity of 69% and 96%, respectively, in predicting the presence of a fetal PCA. The positive predictive value was found to be 82% while a negative predictive value was estimated as 93%. A small-caliber P1 segment and large-caliber posterior communicating artery led to inaccurate interpretations of the CTAs.

CONCLUSION

This study shows that one cannot accurately predict blood supply dominance of the posterior cerebral artery. Knowledge of the blood flow dominance is essential when clipping a posterior communicating artery aneurysm to avoid compromise in posterior circulation.

Update on the management of subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease. Outcome after SAH is mainly determined by the initial severity of the hemorrhage. Neuroimaging, in particular computed tomography, and aneurysm repair techniques, such as coiling and clipping, as well as neurocritical care management, have improved during the last few years. The management of a patient with SAH should have an interdisciplinary approach with case discussions between the neurointensivist, interventionalist and the neurosurgeon. The patient should be treated in a specialized neurointensive care unit of a center with sufficient SAH case volume. Poor-grade patients can be observed for complications and delayed cerebral ischemia through continuous monitoring techniques in addition to transcranial Doppler ultrasonography such as continuous electroencephalography, brain tissue oxygenation, cerebral metabolism, cerebral blood flow and serial vascular imaging. Neurocritical care should focus on neuromonitoring for delayed cerebral ischemia, management of hydrocephalus, seizures and intracranial hypertension, as well as of medical complications such as hyperglycemia, fever and anemia.

Morphological and clinical risk factors for the rupture of anterior communicating artery aneurysms

OBJECT

Patients with ruptured anterior communicating artery (ACoA) aneurysms have historically been observed to have poor neuropsychological outcomes, and ACoA aneurysms have accounted for a higher proportion of ruptured than unruptured aneurysms. Authors of this study aimed to investigate the morphological and clinical characteristics predisposing to ACoA aneurysm rupture.

METHODS

Data from 140 consecutive patients with ACoA aneurysms managed at the authors' facility between July 2003 and November 2011 were retrospectively reviewed. Patients with (78) and without (62) aneurysm rupture were divided into groups, and morphological and clinical characteristics were compared. Morphological characteristics were evaluated based on 3D CT angiography and included aneurysm location, dominance of the A1 portion of the anterior cerebral artery, direction of the aneurysm dome around the ACoA, aneurysm bleb(s), size of the aneurysm and its neck, aneurysm-parent artery angle, and existence of other intracranial unruptured aneurysms.

RESULTS

Patients with ruptured ACoA aneurysms were significantly younger (a higher proportion were younger than 60 years of age) than those with unruptured lesions, and a significantly smaller proportion had hypercholesterolemia. A significantly larger proportion of patients with ruptured aneurysms showed an anterior direction of the aneurysm dome around the ACoA, had a bleb(s), and/or had an aneurysm size ≥ 5 mm. Multivariate logistic regression analysis showed that an anterior direction of the aneurysm dome around the ACoA (OR 6.0, p = 0.0012), the presence of a bleb(s) (OR 22, p < 0.0001), and an aneurysm size ≥ 5 mm (OR 3.16, p = 0.035) were significantly associated with ACoA aneurysm rupture.

CONCLUSIONS

Findings in the present study demonstrated that the anterior projection of an ACoA aneurysm may be related to rupturing. The authors would perhaps recommend treatment to patients with unruptured ACoA aneurysms that have an anterior dome projection, a bleb(s), and a size ≥ 5 mm.

Potent risk factor for aneurysm formation: termination aneurysms of the anterior communicating artery and detection of A1 vessel asymmetry by flow dilution

BACKGROUND AND PURPOSE

There is a high incidence of intracranial aneurysms of the AcomA suggesting the possibility of an anatomic risk factor. There also exists an association of termination-type aneurysms with anatomic variations of 1 anterior cerebral artery trunk (A1) as the exclusive or dominant supply to both pericallosal arteries (A2). This yields the hypotheses of aneurysm formation from straight jets of A1 blood.

MATERIALS AND METHODS

The anatomy and contrast filling of A1 and A2 segments and AcomAs were studied for a subset of cases entered into the Cerecyte Coil Trial for patients with AcomA (n = 105) and other aneurysms (n = 123) that were selected from imaging available at the Cerecyte Core Trial angiographic Core Lab. These cases were analyzed for A1 vessel dominance by measurement of the vessel diameter and dilution of angiographic contrast agent in A2s due to the differential flow source on selective angiography. A control group without aneurysms was assessed anatomically, using a large sequential CTA series (n = 159), acquired during acute stroke assessment.

RESULTS

A1 dominance configuration is strongly associated with the presence of AcomA aneurysms for patients with intracranial aneurysms (odds ratio, 17.8). This association is also present compared with the incidence of A1 dominance in the large sequential control series of patients without aneurysms undergoing CTA for other reasons (odds ratio, 7.5). Outflow dilution of selective angiographic images augments anatomic information.

CONCLUSIONS

A flow-based assessment of contrast flowing from the A1 to the A2 segments after injection pressure is superior to an A1 diameter based categorization when A1 vessel diameters are not strikingly different. The anatomic variant of asymmetric A1 configurations likely facilitates the development of AcomA aneurysms by flow stresses, providing further evidence to support the role of biophysical factors in intracranial aneurysm development.

Multi-detector Computer Tomography Angiography in the Initial Assessment of Patients Acutely Suspected of Having Intracranial Aneurysm Rupture

Introduction: Multi-detector computer tomography angiography (CTA) provides a fast non-invasive assessment of the cerebral vessels, is readily available in an acute setting and can potentially replace invasive digital subtraction angiography (DSA) forthe diagnosis of intracranial vascular lesions in an emergency setting. We report our experience in the use of emergent cerebral CTA versus DSA in the assessment of patients presenting acutely with symptoms suspicious of brain aneurysm rupture. Materials and Methods: Thirty-seven consecutive patients presenting acutely with clinical suspicion of brain aneurysm rupture were evaluated over a 4-month period from January to April 2008. CTA with peripheral intravenous contrast injection was performed on a 32 slice helical scanner. DSA was performed within 48 hours for all cases when CTA was the initial assessment. Studies were assessed via radiology reports using DSA or surgery as the gold standard. Results: All except for 3 patients had CTA as the initial study. There were 26 cerebral aneurysms detected by CTA in these 37 patients, with 9 negative studies. There were 2 patients with arteriovenous malformations (AVM), 1 with AV fistula (AVF), 1 tumoral bleed, 2 vertebral dissections, and 1 missed sagittal sinus thrombosis (CVT) on CTA. Based solely on CTA assessment, 3 patients had direct surgical clipping of the aneurysm, while 4 proceeded to direct endovascular coiling. Conclusion: Emergent CTA is a non-invasive, reliable and viable alternative to emergent DSA for the assessment of the cerebral vessels in the acute assessment of patients presenting with symptoms suspicious of brain aneurysm rupture. Where positive, it can serve as a guide to therapeutic decisions. Review of CTA source data is essential, especially for small lesions and for post-clipping assessment. Key words: Digital subtraction angiography, Intracranial aneurysms, Multi-detector computer tomography angiography

Subarachnoid haemorrhage due to a dissecting aneurysm of the anterior cerebral artery: a case report

Dissecting aneurysms of the intracranial carotid circulation are becoming increasingly recognised as a cause of subarachnoid haemorrhage. We present a case where SAH caused by anterior cerebral artery dissection was diagnosed on a repeat angiogram and successfully treated by surgical trapping. Diagnosis may be difficult as angiographic signs may be subtle and variable. Accurate diagnosis and prompt treatment is important, as the re-bleed rate is high.

How useful is the 3-dimensional, surgeon’s perspective-adjusted visualisation of the vessel anatomy during aneurysm surgery? A prospective clinical trial

We hypothesized that neuronavigational 3-dimensional display of vessel and aneurysm anatomy, which is adjusted to the actual surgeon's view, could be helpful during the critical steps of aneurysm treatment. A total number of 32 patients with 42 aneurysms entered this prospective clinical trial. With a neuronavigational system, a 3-dimensional image of the arterial vascular anatomy was generated by autosegmentation of a computerized tomography (CT) angiographic data set. The 3-dimensional image was then adjusted to the surgeon's perspective by rotation. The neurosurgeon linked the 3-dimensional image information with the vascular structures in his surgical field by a neuronavigational pointer. He had the opportunity to further rotate the image with the displayed pointer for visualization of hidden structures. After operation, the neurosurgeon had to define with which expectations neuronavigation was applied and to evaluate if these expectations were fulfilled. The expectations with which the neurosurgeon used neuronavigation were to localize the aneurysm (n = 24), to understand the branching anatomy (n = 18), to visualize hidden structures (n = 8), to evaluate the projection of the aneurysm dome (n = 5) and to tailor the approach (n = 2). In 5 of the 42 aneurysms that were either very small or located in close vicinity to the skull base, the neurosurgeon's expectations were not fulfilled. A favorable outcome was achieved in 29 of the 32 patients (91%). Neuronavigational 3-dimensional display of the vessel anatomy was considered useful by the vascular neurosurgeon. Possibly, this technique has the potential to improve operative results by reduction of the surgical trauma and avoidance of intraoperative complications.

Anatomic Variations in the Circle of Willis in Patients with Symptomatic Carotid Artery Stenosis Assessed with Multidetector Row CT Angiography

PURPOSE

To assess the presence of anterior and posterior collateral pathways in the circle of Willis in patients with symptomatic carotid artery stenosis (SCAS) and to compare this to patients without carotid artery stenosis.

MATERIALS AND METHODS

Multislice CT angiography was performed in 91 patients and 91 control subjects. Using consensus reading, 2 observers evaluated the presence and diameter of the anterior communicating artery (AcomA), the A1 segments of the anterior cerebral arteries, the posterior communicating arteries (PcomA) and the P1 segments of the posterior cerebral arteries. Anterior or posterior pathways were assumed to be present if the diameter of continuous arterial segments was >1 mm; both A1 segments and AcomA anterior, and ipsilateral P1 segment and PcomA posterior. Comparison between patients and controls was performed using the chi(2) test.

RESULTS

In the patients we found significantly more hypoplastic (<1 mm) or invisible A1 segments (16 and 14 vs. 4 and 1, respectively, p < 0.01). The AcomA was invisible in 4 patients versus 1 control. An isolated compromised anterior pathway and a combined compromised anterior and posterior pathway occurred more frequently in the patients as compared to the controls; 9 versus 1% (p < 0.01) and 26 versus 4% (p < 0.01).

CONCLUSION

A compromised anterior collateral pathway, usually combined with a compromised posterior pathway, occurs more frequently in patients with SCAS as compared to controls, which suggests a relation between symptomatic carotid stenosis and an incomplete circle of Willis.

Acute subarachnoid hemorrhage: using 64-slice multidetector CT angiography to “triage” patients’ treatment

INTRODUCTION

To evaluate the clinical role of CT angiography (CTA) in patients with acute subarachnoid hemorrhage (SAH) for treatment decision-making.

METHODS

Consecutive patients with acute SAH had CTA using a 64-slice scanner for initial clinical decision-making. Image processing included multiplanar volume reformatted (MPVR) maximum intensity projections (MIP) and 3D volume-rendered reconstructions. CTAs were used for (1) evaluating the cause of SAH, and (2) triaging aneurysm-bearing patients to the more appropriate management, either surgical clipping or endovascular coiling. CTA findings were confirmed by neurosurgical exploration or catheter angiography (digital subtraction angiography, DSA). Successful coiling provided evidence that triaging to endovascular treatment was correct.

RESULTS

Included in the study were 73 patients. CTA findings were confirmed by DSA or neurosurgical operation in 65 patients, and of these 65, 47 had aneurysmal SAH, 3 had vasculitis, 1 had arterial dissection and 14 had no underlying arterial abnormality. The cause of SAH was detected with CTA in 62 out of the 65 patients (95.4%, sensitivity 94%, specificity 100%). CTA revealed the aneurysm in 46 of 47 patients (98%, sensitivity 98%, specificity 100%, positive predictive value 100%, negative predictive value 82.3%), 1 of 3 vasculitides and 1 of 1 dissection. Of the 46 patients with aneurysm, 44 (95.7%) were referred for treatment based on CTA. In 2 patients (2 of 46, 4.4%) CTA was not informative enough to choose treatment requiring DSA. Of the 44 patients, 27 (61.4%) were referred to endovascular treatment and successful coiling was achieved in 25 (25 of 27, 92.6%).

CONCLUSION

CTA using a 64-slice scanner is an accurate tool for detecting and characterizing aneurysms in acute SAH. CTA is useful in the decision process whether to coil or clip an aneurysm.

Detection and evaluation of intracranial aneurysms with 16-row multislice CT angiography

AIM

The aim of this study was to assess the usefulness of 16-row multislice CT angiography (CTA) in evaluating intracranial aneurysms, by comparison with conventional digital subtraction angiography (DSA) and intraoperative findings.

METHODS

A consecutive series of 57 patients, scheduled for DSA for suspected intracranial aneurysm, was prospectively recruited to have CTA. This was performed with a 16-detector row machine, detector interval 0.75 mm, 0.5 rotation/s, table speed 10mm/rotation and reconstruction interval 0.40 mm. CTA studies were independently and randomly assessed by two neuroradiologists and a vascular neurosurgeon blinded to the DSA and surgical findings. Review of CTA was performed on workstations with an interactive 3D volume-rendered algorithm.

RESULTS

DSA or intraoperative findings or both confirmed 53 aneurysms in 44 patients. For both independent readers, sensitivity and specificity per aneurysm of DSA were 96.2% and 100%, respectively. Sensitivity and specificity of CTA were also 96.2% and 100%, respectively. Mean diameter of aneurysms was 6.3mm (range 1.9 to 28.1 mm, SD 5.2 mm). For aneurysms of less than 3 mm, CTA had a sensitivity of 91.7% for each reader. Although the neurosurgeon would have been happy to proceed to surgery on the basis of CTA alone in all cases, he judged that DSA might have provided helpful additional anatomical information in 5 patients.

CONCLUSION

The diagnostic accuracy of 16-slice CTA is promising and appears equivalent to that of DSA for detection and evaluation of intracranial aneurysms. A strategy of using CTA as the primary imaging method, with DSA reserved for cases of uncertainty, appears to be practical and safe.

Current diagnostic approaches to subarachnoid haemorrhage

Over the past decade, significant advances have been made in the field of subarachnoid haemorrhage (SAH). Prompt diagnosis with high-resolution CT and intensive critical care support remain key aspects of good patient management. Early identification and definitive treatment of underlying ruptured aneurysms is generally advocated to reduce the risk of re-bleeding, a complication with high mortality and morbidity. Although intra-arterial digital subtraction angiography (DSA) is still considered the gold standard for sourcing aneurysms, CT angiography, especially with the evolution of multi-slice technology, is slowly gaining acceptance as a rapid, accessible and minimally invasive method which appears likely to replace DSA as first-line modality in the future. Furthermore, the advent of Guglielmi detachable coils and the ISAT trial have revolutionised the treatment of ruptured aneurysms, with a significant trend towards endovascular coiling away from operative clipping. Improvements in clinical experience, coiling technology and assistive devices now allow interventionalists to potentially treat the majority of aneurysms, including wide-necked or complex lesions. The uncertain long-term results of coiling, however, still fuel strong debate and controversy. This review summarises current diagnostic approaches to SAH from a radiological perspective, with an emphasis on aneurysmal SAH and an evidence-based approach to the role of imaging and interventional radiology in diagnosis, treatment and follow-up.

Intracranial aneurysms: evaluation using CTA and MRA. Correlation with DSA and intraoperative findings

Computed tomographic angiography (CTA) and magnetic resonance angiography (MSA) have been used recently for evaluation of intracranial aneurysms. If they are to replace conventional digital subtraction angiography (DSA), their sensitivity and specificity should be equal to the latter. In order to determine whether computed tomographic angiography and magnetic resonance angiography can provide the necessary information for presurgical evaluation we compared blindly the results of helical CT angiography and MR angiography with the results of digital subtraction angiography and the intraoperative findings. We evaluated 35 patients with the possible clinical diagnosis of intracranial aneurysm. Our data suggest that both CTA and MRA can provide valuable preoperative information concerning the location, the characteristics and the relationships of most intracranial aneurysms. Both original and reconstructed images should be evaluated together for higher accuracy. In addition helical CT, being a fast, inexpensive and noninvasive method, can be used as a reliable alternative to DSA in emergency situations demanding immediate operation.

Current usage of three-dimensional computed tomography angiography for the diagnosis and treatment of ruptured cerebral aneurysms

Our previous study suggested that 3D-CT angiography could replace digital subtraction (DS) angiography in most cases of ruptured cerebral aneurysms, especially in the anterior circulation. This study reviewed our further experience. One hundred and fifty patients with ruptured cerebral aneurysms were treated between November 1998 and March 2002. Only 3D-CT angiography was used for the preoperative work-up study in patients with anterior circulation aneurysms, unless the attending neurosurgeons agreed that DS angiography was required. Both 3D-CT angiography and DS angiography were performed in patients with posterior circulation aneurysms, except for recent cases that were possibly treated with 3D-CT angiography alone. One hundred sixteen (84%) of 138 patients with ruptured anterior circulation aneurysms underwent surgical treatment, but additional DS angiography was required in 22 cases (16%). Only two recent patients were treated surgically with 3D-CT angiography alone in 12 patients with posterior circulation aneurysms. Most patients with ruptured anterior circulation aneurysms could be treated successfully after 3D-CT angiography alone. However, additional DS angiography is still necessary in atypical cases. 3D-CT angiography may be limited to complementary use in patients with ruptured posterior circulation aneurysms.

Detection of Intracranial Aneurysms: Multi–Detector Row CT Angiography Compared with DSA

PURPOSE

To prospectively compare the effectiveness of multi-detector row computed tomographic (CT) angiography with that of conventional intraarterial digital subtraction angiography (DSA) used to detect intracranial aneurysms in patients with nontraumatic acute subarachnoid hemorrhage.

MATERIALS AND METHODS

Thirty-five consecutive adult patients with acute subarachnoid hemorrhage were recruited into the institutional review board-approved study and gave informed consent. All patients underwent both multi-detector row CT angiography and DSA no more than 12 hours apart. CT angiography was performed with a multi-detector row scanner (four detector rows) by using collimation of 1.25 mm and pitch of 3. Images were interpreted at computer workstations in a blinded fashion. Two radiologists independently reviewed the CT images, and two other radiologists independently reviewed the DSA images. The presence and location of aneurysms were rated on a five-point scale for certainty. Sensitivity and specificity were calculated independently for image interpretation performed by the two CT image readers and the second DSA image reader by using the first DSA reader's interpretation as the reference standard.

RESULTS

A total of 26 aneurysms were detected at DSA in 21 patients, and no aneurysms were detected in 14 patients. Sensitivity and specificity for CT angiography were, respectively, 90% and 93% for reader 1 and 81% and 93% for reader 2. The mean diameter of aneurysms detected on CT angiographic images was 4.4 mm, and the smallest aneurysm detected was 2.2 mm in diameter. Aneurysms that were missed at initial interpretation of CT angiographic images were identified at retrospective reading.

CONCLUSION

Multi-detector row CT angiography has high sensitivity and specificity for detection of intracranial aneurysms, including small aneurysms, in patients with nontraumatic acute subarachnoid hemorrhage.