Ultra-High-Resolution Time-of-Flight MR-Angiography for the Noninvasive Assessment of Intracranial Aneurysms, Alternative to Preinterventional DSA?

PURPOSE: The 3D time-of-flight (TOF) magnetic resonance angiography (MRA) at 3T shows high sensitivity for intracranial aneurysms but is inferior to three-dimensional digital subtraction angiography (3D-DSA) regarding aneurysm characteristics. We applied an ultra-high-resolution (UHR) TOF-MRA using compressed sensing reconstruction to investigate the diagnostic performance in preinterventional evaluation of intracranial aneurysms compared to conventional TOF-MRA and 3D-DSA. METHODS: In this study 17 patients with unruptured intracranial aneurysms were included. Aneurysm dimensions, configuration, image quality and sizing of endovascular devices were compared between conventional TOF-MRA at 3T and UHR-TOF with 3D-DSA as gold standard. Quantitatively, contrast-to-noise ratios (CNR) were compared between TOF-MRAs. RESULTS: On 3D-DSA, 25 aneurysms in 17 patients were detected. On conventional TOF, 23 aneurysms were detected (sensitivity: 92.6%). On UHR-TOF, 25 aneurysms were detected (sensitivity: 100%). Image quality was not significantly different between TOF and UHR-TOF (p = 0.17). Aneurysm dimension measurements were significantly different between conventional TOF (3.89 mm) and 3D-DSA (4.2 mm, p = 0.08) but not between UHR-TOF (4.12 mm) and 3D-DSA (p = 0.19). Irregularities and small vessels at the aneurysm neck were more frequently correctly depicted on UHR-TOF compared to conventional TOF. Comparison of the planned framing coil diameter and flow-diverter (FD) diameter revealed neither a statistically significant difference between TOF and 3D-DSA (coil p = 0.19, FD p = 0.45) nor between UHR-TOF and 3D-DSA (coil: p = 0.53, FD 0.33). The CNR was significantly higher in conventional TOF (p = 0.009). CONCLUSION: In this pilot study, ultra-high-resolution TOF-MRA visualized all aneurysms and accurately depicted aneurysm irregularities and vessels at the base of the aneurysm comparably to DSA, outperforming conventional TOF. UHR-TOF with compressed sensing reconstruction seems to represent a non-invasive alternative to pre-interventional DSA for intracranial aneurysms.

Quantitative assessment of microstructural evolution of intracranial aneurysm wall by vessel wall imaging.

PURPOSE: This study aimed to evaluate new quantitative parameters of aneurysm wall enhancement (AWE) on magnetic resonance vessel wall imaging (VWI) in differentiating between the stable and evolving unruptured intracranial aneurysms (UIAs). METHODS: Thirty-eight consecutive patients with UIAs (27 stable and 11 evolving) underwent VWI with contrast-enhanced 3D T1 volume isotropic turbo spin echo acquisition. The voxel-based enhancement maps were created using pre- and post-contrast images. The aneurysmal lumen with signal suppression by black-blood method was segmented. Then, one voxel outer and inner layers of the lumen contour were automatically segmented. The shape features of the aneurysms and AWE of the two layers were compared between stable and evolving groups. RESULTS: The shape features, including aneurysm volume, surface, and compacity were significantly different between the stable and evolving groups (P = 0.024, 0.028, and 0.033, respectively). Stable and evolving groups also differed significantly in the AWE at the union of outer and inner layers of the aneurysm wall (P = 0.0082) but not in that of the outer or inner layer alone. Multivariate logistic regression analysis revealed significant differences in aneurysm volume, surface, and AWE at the union of outer and inner layers between the two groups (P = 0.0029, 0.0092, and 0.0033, respectively). Receiver operating characteristics curve analysis revealed that the area under the curve of the logistic regression model was 0.89. CONCLUSION: Quantitative combined analysis of aneurysm shape features and AWE of the union of outer and inner layers were effective for differentiating between stable and evolving UIAs.

Cost-Effectiveness Analytic Comparison of Neuroimaging Follow-Up Strategies After Pipeline Embolization Device Treatment of Unruptured Intracranial Aneurysms.

BACKGROUND: Flow diversion via a Pipeline embolization device (PED [Medtronic, Dublin, Ireland]) is one of the established modalities for the treatment of unruptured intracranial aneurysms that require a robust follow-up regimen. However, to date, no consensus has been reached regarding the optimal imaging modality and timing intervals for such a strategy. We studied the cost-effectiveness of different neuroimaging follow-up strategies after flow diversion with the PED. METHODS: A decision-analytical study using Markov modeling was performed to compare 5 commonly used multistep follow-up strategies with different combinations of digital subtraction angiography (DSA) and magnetic resonance angiography (MRA): 1) DSA at 6 months and MRA at 12 and 24 months; 2) DSA at 6, 12, and 24 months; 3) MRA at 6, 12, and 24 months; 4) DSA at 6 and 12 months and MRA at 24 months; and 5) DSA at 12 months and MRA at 24 months. The input parameters were mainly collected from the latest meta-analysis, and 1-way, 2-way, and probabilistic sensitivity analyses were conducted to assess the robustness of our model. RESULTS: Strategy 5, incorporating DSA at 12 months and MRA at 24 months, was the most cost-effective strategy for >99% of the 10,000 iterations in the probabilistic sensitivity analysis at a willingness-to-pay threshold of $100,000/quality-adjusted life-year. The result remained robust in the 1- and 2-way sensitivity analyses. CONCLUSIONS: Given the current data, delayed imaging follow-up at 1 year with DSA and 2 years with MRA after PED treatment of unruptured intracranial aneurysms is more cost-effective than early follow-up at 6 months.

Evaluation of disease severity and treatment intensity as cost drivers for ruptured intracranial aneurysms.

BACKGROUND: Previous studies have not evaluated the impact of illness severity and postrupture procedures in the cost of care for intracranial aneurysms. We hypothesize that the severity of aneurysm rupture and the aggressiveness of postrupture interventions play a role in cost. METHODS: The Value Driven Outcomes database was used to assess direct patient cost during the treatment of ruptured intracranial aneurysm with clipping, coiling, and Pipeline flow diverters. RESULTS: One hundred ninety-eight patients (mean age 52.8 ± 14.1 years; 40.0% male) underwent craniotomy (64.6%), coiling (26.7%), or flow diversion (8.6%). Coiling was 1.4× more expensive than clipping (p = .005) and flow diversion was 1.7× more expensive than clipping (p < .001). More severe illness as measured by American Society of Anesthesia, Hunt/Hess, and Fisher scales incurred higher costs than less severe illness (p < .05). Use of a lumbar drain protocol to reduce subarachnoid hemorrhage and use of an external ventricular drain to manage intracranial pressure were associated with reduced (p = .05) and increased (p < .001) total costs, respectively. Patients with severe vasospasm (p < .005), those that received shunts (p < .001), and those who had complications (p < .001) had higher costs. Multivariate analysis showed that procedure type, length of stay, number of angiograms, vasospasm severity, disposition, and year of treatment were independent predictors of cost. CONCLUSIONS: These results show for the first time that disease and vasospasm severity and intensity of treatment directly impact the cost of care for patients with aneurysms in the USA. Strategies to alter these variables may prove important for cost reduction.

Aneurysm wall cellularity affects healing after coil embolization: assessment in a rat saccular aneurysm model.

BACKGROUND AND PURPOSE: Despite significant technical advances, recanalization rates after endovascular therapy of ruptured intracranial aneurysms (IAs) remain a clinical challenge. A histopathological hallmark of ruptured human IA walls is mural cell loss. Mural smooth muscle cells (SMCs) are known to promote intraluminal healing in thrombosed experimental aneurysms. In this rat model we assess the natural history and healing process after coil embolization in SMC-rich and decellularized aneurysms. METHODS: Saccular aneurysms were created by end-to-side anastomosis of an arterial graft from the descending thoracic aorta of a syngeneic donor rat to the infrarenal abdominal aorta of recipient male Wistar rats. Untreated arterial grafts were immediately transplanted, whereas aneurysms with loss of mural cells were chemically decellularized before implantation. Aneurysms underwent coil implantation during aneurysm anastomosis. Animals were randomly assigned either to the non-decellularized or decellularized group and underwent macroscopic and histological analyses on days 3, 7, 21, or 90 post-coil implantation. RESULTS: A total of 55 rats underwent macroscopic and histologic analysis. After coil embolization, aneurysms with SMC-rich walls showed a linear course of thrombosis and neointima formation whereas decellularized aneurysms showed marked inflammatory wall degeneration with increased recanalization rates 21 days (p=0.002) and 90 days (p=0.037) later. The SMCs showed the ability to actively migrate into the intra-aneurysmal thrombus and participate in thrombus organization. CONCLUSIONS: Coil embolization of aneurysms with highly degenerated walls is prone to further wall degeneration, increased inflammation, and recanalization compared with aneurysms with vital SMC-rich walls.

Volumetric assessment of extracranial carotid artery aneurysms.

The extracranial carotid artery aneurysm (ECAA) is a rare pathology for which clinical treatment guidelines are lacking. In general, symptoms or growth of the aneurysm sac are thought to indicate intervention. ECAAs may present in a large variety of shapes and sizes, and conventional diameter measurements fail to indicate geometrical differences. Therefore, we propose a protocol to measure ECAA size by 3D volumetric assessment. The volumes of 40 ECAAs in computed tomography angiography (CTA) images were measured through manual segmentation, by two independent operators. Volumes of the entire internal carotid artery (ICA) and the ECAA were measured separately. Excellent inter- and intraoperator reliability was found for both ICA and ECAA volumes, with all intraclass correlation coefficients above 0.94. Bland-Altman analysis revealed normal differences for both inter- and intraoperator agreement. For all volumes, similarity of the segmentations was excellent. Outliers were explained by presence of intraluminal ECAA thrombus, which hampered identification of the aneurysm outer wall. These results implicate robustness of our protocol, which is designed as a step-up towards (semi)automatic volumetric measurements to monitor patients with ECAA. Future (semi)automatic volumetric assessments are recommended and such techniques can be developed and validated using the proposed protocol and manual reference segmentations.

Comparative effectiveness analysis of Pipeline device versus coiling in unruptured aneurysms smaller than 10 mm.

OBJECTIVE: Both endovascular coiling and the Pipeline embolization device (PED) have been shown to be safe and clinically effective for treatment of small (< 10 mm) aneurysms. The authors conducted a comparative effectiveness analysis to compare the utility of these treatment methods in terms of health benefits. METHODS: A decision-analytical study was performed with Markov modeling methods to simulate patients with small unruptured aneurysms undergoing endovascular coiling, stent-assisted coiling (SAC), or PED placement for treatment. Input probabilities were derived from prior literature, and 1-way, 2-way, and probabilistic sensitivity analyses were performed to assess model and input parameter uncertainty. RESULTS: The base case calculation for a 50-year-old man reveals PED to have a higher health benefit (17.48 quality-adjusted life years [QALYs]) than coiling (17.44 QALYs) or SAC (17.36 QALYs). PED is the better option in 6020 of the 10,000 iterations in probabilistic sensitivity analysis. When the retreatment rate of PED is lower than 9.53%, and the coiling retreatment is higher than 15.6%, PED is the better strategy. In the 2-way sensitivity analysis varying the retreatment rates from both treatment modalities, when the retreatment rate of PED is approximately 14% lower than the retreatment rate of coiling, PED is the more favorable treatment strategy. Otherwise, coiling is more effective. SAC may be better than PED when the unfavorable outcome risk of SAC is lower than 70% of its reported current value. CONCLUSIONS: With the increasing use of PEDs for treatment of small unruptured aneurysms, the current study indicates that these devices may have higher health benefits due to lower rates of retreatment compared to both simple coiling and stent-assisted techniques. Longer follow-up studies are needed to document the rates of recurrence and retreatment after coiling and PED to assess the cost-effectiveness of these strategies.

Patency of anterior choroidal artery after flow diverter deployment with assessment of magnetic resonance imaging follow-up.

PURPOSE: We aimed to analyse the patency rate of the anterior choroidal artery, and presented imaging and neurological findings, after deployment of a flow diverter in the anterior choroidal artery in the treatment of patients with intracranial aneurysms. METHODS: Among the 139 patients who underwent a flow diverter deployment from December 2012 to September 2017 in our hospital, there were 21 patients (15.1%) for whom their anterior choroidal artery was covered for the procedure with a flow diverter. The patients' age, sex, size of aneurysm and the presence or absence of an anterior choroidal artery occlusion, neurological findings and postoperative infarction in the anterior choroidal artery region were analysed retrospectively. RESULTS: The mean age of the six male and 15 female patients was 61.5 years (range 32-77 years). The mean maximal diameter of the aneurysms was 16.4 mm (range 10.0-29.4 mm). The anterior choroidal artery was patent in all 21 patients; however, a haemodynamic alteration in the anterior choroidal artery was detected in one patient. Postoperatively, hemiparesis was observed in two patients (9.5%) and a visual field defect in one patient (4.8%), both of which were the symptoms of infarction of the cortical branch of the middle cerebral artery or retinal artery ischaemia. However, no patients had symptoms due to ischaemia of the anterior choroidal artery confirmed with magnetic resonance imaging. CONCLUSIONS: In all patients who underwent flow diverter deployment, the anterior choroidal artery was patent and no ischaemia was detected in the imaging or evidenced by neurological findings. Therefore, flow diverter deployment in the anterior choroidal artery was considered to be a safe procedure.

Anatomical assessment of the endoscopic endonasal approach for the treatment of paraclinoid aneurysms.

OBJECTIVE: Endoscopic endonasal approaches (EEAs) are increasingly being incorporated into the neurosurgeon's armamentarium for treatment of various pathologies, including paraclinoid aneurysms. However, few anatomical assessments have been performed on the use of EEA for this purpose. The aim of the present study was to provide a comprehensive anatomical assessment of the EEA for the treatment of paraclinoid aneurysms. METHODS: Five cadaveric heads underwent an endonasal transplanum-transtuberculum approach to expose the paraclinoid area. The feasibility of obtaining proximal and distal internal carotid artery (ICA) control as well as the topographic location of the origin of the ophthalmic artery (OphA) relative to dural landmarks were assessed. Limitations of the EEA in exposing the supraclinoid ICA were also recorded to identify favorable paraclinoid ICA aneurysm projections for EEA. RESULTS: The extracavernous paraclival and clinoidal ICAs were favorable segments for establishing proximal control. Clipping the extracavernous ICA risked injury to the trigeminal and abducens nerves, whereas clipping the clinoidal segment put the oculomotor nerve at risk. The OphA origin was found within 4 mm of the medial opticocarotid point on a line connecting the midtubercular recess point to the medial vertex of the lateral opticocarotid recess. An average 7.2-mm length of the supraclinoid ICA could be safely clipped for distal control. Assessments showed that small superiorly or medially projecting aneurysms were favorable candidates for clipping via EEA. CONCLUSIONS: When used for paraclinoid aneurysms, the EEA carries certain risks to adjacent neurovascular structures during proximal control, dural opening, and distal control. While some authors have promoted this approach as feasible, this work demonstrates that it has significant limitations and may only be appropriate in highly selected cases that are not amenable to coiling or clipping. Further clinical experience with this approach helps to delineate its risks and benefits.

Cerebral Aneurysm Size and Distal Intracranial Hemodynamics: An Assessment of Flow and Pulsatility Index Using Quantitative Magnetic Resonance Angiography.

BACKGROUND: The relationship between cerebral aneurysm size and risk of rupture is well documented, but the impact of aneurysms on distal intracranial hemodynamics is unknown. OBJECTIVE: To examine the relationship between aneurysm size and distal intracranial hemodynamics prior to treatment. METHODS: Patients seen at our institution between 2006 and 2015 with cerebral aneurysms within the internal carotid artery (ICA) segments (proximal to ICA terminus) were retrospectively reviewed. Patients were included if the aneurysm was unruptured, and were excluded if a contralateral aneurysm was present. Flows within bilateral ICAs and middle cerebral arteries (MCA) were measured prior to any treatment using quantitative magnetic resonance angiography. Pulsatility index (PI = [systolic - diastolic flow velocity]/mean flow velocity) within each vessel was then calculated. Hemodynamic parameters were analyzed with respect to aneurysm size. RESULTS: Forty-two patients were included. Mean aneurysm size was 13.5 mm (range 2-40 mm). There was a significant correlation between aneurysm size and ipsilateral MCA PI (P = .006; r = 0.441), MCAipsilateral/ICAipsilateral PI ratio (P = .003; r = 0.57), and MCAipsilateral/MCAcontralateral PI ratio (P = .008; r = 0.43). Mean PI in the ipsilateral ICA was 0.38 (range 0.17-0.77) and ipsilateral MCA was 0.31 (range 0.08-0.83), and mean PI in contralateral ICA was 0.35 (range 0.19-0.57) and MCA was 0.30 (range 0.07-0.89). CONCLUSION: Larger aneurysm size correlates with higher ipsilateral MCA PI, demonstrating that aneurysms affect distal intracranial hemodynamics.

Assessment of endothelialization of aneurysm wall over time in a rabbit model through CD31 scoring.

BACKGROUND: Intracranial aneurysms represent a significant health concern and are poorly understood despite decades of research. Our study focused on understanding temporal patterns of endothelial cell distribution in different spatial locations within the aneurysm early after creation in a rabbit model. METHODS: Elastase induced saccular aneurysms were created in rabbits and harvested on day 1 (n=3) and after 2 (n=5), 4 (n=4), 8 (n=5), and 12 (n=6) weeks. Sham operated controls (n=3) were harvested on the same day. Aneurysm and control tissue samples were subjected to en face whole mount CD31 staining for endothelial cells. Semiquantitative scoring was performed on the basis of endothelial coverage of the vessel wall (proximal, middle, and distal portions of the aneurysm dome). Mixed effects models were used to assess the effect of time and aneurysm section on endothelial coverage. RESULTS: Aneurysmal segments were near completely de-endothelialized at 4 and 8 weeks but had re-endothelialized by 12 weeks. Compared with controls, aneurysms at all time points showed decreased endothelialization, but the difference was only significant compared with the 4 and 8 week groups. Both time (P=0.03) and aneurysm section (P=0.07) were significantly associated with the degree of endothelialization. Proximal locations showed increased endothelialization compared with distal locations (P=0.03). CONCLUSION: In experimental aneurysms of rabbits, endothelial cells regress during the first month after creation, followed by ascending re-endothelialization that stays incomplete. These findings suggest that re-population of endothelial cells comes from resident cells in the adjacent parent artery and that deranged hemodynamics may affect full reconstitution of endothelial cells long term.

Quantitative Assessment of Circumferential Enhancement along the Wall of Cerebral Aneurysms Using MR Imaging.

BACKGROUND AND PURPOSE: The incidence of wall enhancement of cerebral aneurysms on vessel wall MR imaging has been described as higher in ruptured intracranial aneurysms than in unruptured intracranial aneurysms, but the difference in the degree of enhancement between ruptured and unruptured aneurysms is unknown. We compared the degree of enhancement between ruptured and unruptured intracranial aneurysms by using quantitative MR imaging measures. MATERIALS AND METHODS: We performed quantitative analyses of circumferential enhancement along the wall of cerebral aneurysms in 28 ruptured and 76 unruptured consecutive cases by using vessel wall MR imaging. A 3D-T1-weighted fast spin-echo sequence was obtained before and after contrast media injection, and the wall enhancement index was calculated. We then compared characteristics between ruptured and unruptured aneurysms. RESULTS: The wall enhancement index was significantly higher in ruptured than in unruptured aneurysms (1.70 ± 1.06 versus 0.89 ± 0.88, respectively; P = .0001). The receiver operating characteristic curve analysis found that the most reliable cutoff value of the wall enhancement index to differentiate ruptured from unruptured aneurysms was 0.53 (sensitivity, 0.96; specificity, 0.47). The wall enhancement index remained significant in the multivariate logistic regression analysis (P < .0001). CONCLUSIONS: Greater circumferential enhancement along the wall of cerebral aneurysms correlates with the ruptured state. A quantitative evaluation of circumferential enhancement by using vessel wall MR imaging could be useful in differentiating ruptured from unruptured intracranial aneurysms.

Assessment of the Endoscopic Endonasal Transclival Approach for Surgical Clipping of Anterior Pontine Anterior-Inferior Cerebellar Artery Aneurysms.

OBJECTIVE: Aneurysms of the anterior pontine segment of the anterior-inferior cerebellar artery (AICA) are uncommon. Their treatment is challenging because critical neurovascular structures are adjacent to it and the available surgical corridors are narrow and deep. Although endoscopic endonasal approaches are accepted for treating midline skull base lesions, their role in the treatment vascular lesions remains undefined. The present study is aimed to assess the anatomic feasibility of the endoscopic endonasal transclival (EET) approach for treating anterior pontine AICA aneurysms and compare it with the subtemporal anterior transpetrosal (SAT) approach. METHODS: Twelve cadaveric specimens were prepared for surgical simulation. The AICAs were exposed using both EET and SAT approaches. Surgical window area and the length of the exposed artery were measured. The distance from the origin of the artery to the clip applied for proximal control was measured. The number of AICA perforators exposed and the anatomic features of each AICA were recorded. RESULTS: The EET approach provided a wider surgical window area compared with the SAT (P < 0.001). More AICA perforators were visualized using the EET approach (P < 0.05). To obtain proximal control of the AICA, an aneurysm clip could be applied closer to the origin of AICA using EET (0.2 ± 0.42 mm) compared with SAT (6.26 ± 3.4 mm) (P < 0.001). CONCLUSION: Clipping anterior pontine AICA aneurysms using the EET approach is feasible. Compared with SAT, the EET approach provides advantages in surgical window area, ensuring proximal control before aneurysm dissection, visualization of perforating branches, and better proximal control.

Assessment of image-derived risk factors for natural course of unruptured cerebral aneurysms.

OBJECTIVE: The goal of this prospective longitudinal study was to test whether image-derived metrics can differentiate unruptured aneurysms that will become unstable (grow and/or rupture) from those that will remain stable. METHODS: One hundred seventy-eight patients harboring 198 unruptured cerebral aneurysms for whom clinical observation and follow-up with imaging surveillance was recommended at 4 clinical centers were prospectively recruited into this study. Imaging data (predominantly CT angiography) at initial presentation was recorded. Computational geometry was used to estimate numerous metrics of aneurysm morphology that described the size and shape of the aneurysm. The nonlinear, finite element method was used to estimate uniform pressure-induced peak wall tension. Computational fluid dynamics was used to estimate blood flow metrics. The median follow-up period was 645 days. Longitudinal outcome data on these aneurysm patients-whether their aneurysms grew or ruptured (the unstable group) or remained unchanged (the stable group)-was documented based on follow-up at 4 years after the beginning of recruitment. RESULTS: Twenty aneurysms (10.1%) grew, but none ruptured. One hundred forty-nine aneurysms (75.3%) remained stable and 29 (14.6%) were lost to follow-up. None of the metrics-including aneurysm size, nonsphericity index, peak wall tension, and low shear stress area-differentiated the stable from unstable groups with statistical significance. CONCLUSIONS: The findings in this highly selected group do not support the hypothesis that image-derived metrics can predict aneurysm growth in patients who have been selected for observation and imaging surveillance. If aneurysm shape is a significant determinant of invasive versus expectant management, selection bias is a key limitation of this study.

Practises and controversies in the management of asymptomatic aneurysms: Results of an international survey.

BACKGROUND: Asymptomatic aneurysms that are increasingly discovered on cranial diagnostic imaging are a growing management dilemma. Large-scale studies have shown that in most instances, conservative management is appropriate for the majority of patients with aneurysms less than 7 mm in maximum diameter. It is unclear whether international practise mirrors practise in these large trials. OBJECTIVE: To determine how neurosurgeons around the world manage patients with asymptomatic aneurysms. METHODS: Electronic survey of 283 clinicians managing patients with aneurysms using a 55-item questionnaire detailing characteristics of their experience, their hospitals and their present and future practises and insights regarding the management of patients with intracerebral aneurysms. RESULTS: The 203 neurosurgeons (72%) who responded had a median of 17 years of practise with aneurysms and managed a median of 25 aneurysms annually. The majority of neurosurgeons endorsed treatment of all asymptomatic aneurysms regardless of size. Only four out of 10 neurosurgeons would manage patients with 4 mm anterior communicating artery or middle cerebral artery aneurysms non-surgically, whereas fewer than 2% would conservatively manage asymptomatic patients with 10 or 16 mm aneurysms. Neurosurgeons were split as to the recommended techniques for asymptomatic aneurysms of 10 or 16 mm with about half of them electing clipping and half coiling for ACoA and nearly three quarters favouring clipping for the MCA aneurysm. Although international differences exist between Europe, North America and the rest of the world, most state that their choice of treatment related to decisions around what option would provide the best neurological outcome and prevention of long-term bleeding. CONCLUSION: Despite large trials supporting the management of small asymptomatic aneurysms, most neurosurgeons internationally chooses to treat them with surgery or endovascular means. Since clinicians use a number of factors beyond the maximum diameter when considering treatment options, future trials should consider these factors in their design.

The Utility of Dual-Energy Computed Tomographic Angiography for the Evaluation of Brain Aneurysms After Surgical Clipping: A Prospective Study.

OBJECTIVE: The purpose of this prospective study was to compare a novel dual-energy computed tomographic angiography (DECTA) method for postoperative assessment of clipped brain aneurysms to detect aneurysm remnants and parent artery patency, with catheter-based digital subtraction angiography (DSA). METHODS: Patients who underwent microsurgical cerebral aneurysm repair were prospectively evaluated after surgery by both DECTA and conventional DSA. CTA was performed using a novel dual-energy method with single source and fast kilovoltage switching (Gemstone Spectral Imaging [GSI]). DSA was performed using biplanar cerebral angiography. An experienced neuroradiologist and a neurosurgeon, both blinded to the original radiologic results, reviewed the images. RESULTS: On DSA, 8 of 15 aneurysms (53%) had a remnant after clipping. All of these remnants were <2 mm except for 1. The only residual aneurysm >2 mm was clearly detected by GSI CTA. Of those 7 DSA-confirmed <2-mm remnants, 5 were detected by GSI CTA. Metal artifacts compromised the image quality in 2 patients. The sensitivity and specificity of GSI CTA for remnant aneurysm <2-mm detection in single clip-treated patients were 100%. In all patients, these were 71.4 % and 100%, respectively. GSI CTA was 100% sensitive and 77% specific to detect parent vessel compromise, with associated positive and negative predictive values of 60% and 100%, respectively. CONCLUSIONS: DECTA is a promising noninvasive alternative to conventional catheter-based angiography for identification of aneurysm remnants and assessment of adjacent arteries after surgical clipping of brain aneurysms treated by 2 or fewer clips. It allows for a more rapid image acquisition than DSA, is more cost effective, and is widely available at clinical centers.

Quantifying Intracranial Aneurysm Wall Permeability for Risk Assessment Using Dynamic Contrast-Enhanced MRI: A Pilot Study.

BACKGROUND AND PURPOSE: Pathological changes in the intracranial aneurysm wall may lead to increases in its permeability; however the clinical significance of such changes has not been explored. The purpose of this pilot study was to quantify intracranial aneurysm wall permeability (K(trans), VL) to contrast agent as a measure of aneurysm rupture risk and compare these parameters against other established measures of rupture risk. We hypothesized K(trans) would be associated with intracranial aneurysm rupture risk as defined by various anatomic, imaging, and clinical risk factors. MATERIALS AND METHODS: Twenty-seven unruptured intracranial aneurysms in 23 patients were imaged with dynamic contrast-enhanced MR imaging, and wall permeability parameters (K(trans), VL) were measured in regions adjacent to the aneurysm wall and along the paired control MCA by 2 blinded observers. K(trans) and VL were evaluated as markers of rupture risk by comparing them against established clinical (symptomatic lesions) and anatomic (size, location, morphology, multiplicity) risk metrics. RESULTS: Interobserver agreement was strong as shown in regression analysis (R(2) > 0.84) and intraclass correlation (intraclass correlation coefficient >0.92), indicating that the K(trans) can be reliably assessed clinically. All intracranial aneurysms had a pronounced increase in wall permeability compared with the paired healthy MCA (P < .001). Regression analysis demonstrated a significant trend toward an increased K(trans) with increasing aneurysm size (P < .001). Logistic regression showed that K(trans) also predicted risk in anatomic (P = .02) and combined anatomic/clinical (P = .03) groups independent of size. CONCLUSIONS: We report the first evidence of dynamic contrast-enhanced MR imaging-modeled contrast permeability in intracranial aneurysms. We found that contrast agent permeability across the aneurysm wall correlated significantly with both aneurysm size and size-independent anatomic risk factors. In addition, K(trans) was a significant and size-independent predictor of morphologically and clinically defined high-risk aneurysms.

Development of three-dimensional hollow elastic model for cerebral aneurysm clipping simulation enabling rapid and low cost prototyping.

OBJECTIVE: We developed a method for fabricating a three-dimensional hollow and elastic aneurysm model useful for surgical simulation and surgical training. In this article, we explain the hollow elastic model prototyping method and report on the effects of applying it to presurgical simulation and surgical training. METHODS: A three-dimensional printer using acrylonitrile-butadiene-styrene as a modeling material was used to produce a vessel model. The prototype was then coated with liquid silicone. After the silicone had hardened, the acrylonitrile-butadiene-styrene was melted with xylene and removed, leaving an outer layer as a hollow elastic model. RESULTS: Simulations using the hollow elastic model were performed in 12 patients. In all patients, the clipping proceeded as scheduled. The surgeon's postoperative assessment was favorable in all cases. This method enables easy fabrication at low cost. CONCLUSION: Simulation using the hollow elastic model is thought to be useful for understanding of three-dimensional aneurysm structure.

Safety, efficacy, and cost of intraoperative indocyanine green angiography compared to intraoperative catheter angiography in cerebral aneurysm surgery.

Intraoperative angiography in cerebrovascular neurosurgery can drive the repositioning or addition of aneurysm clips. Our institution has switched from a strategy of intraoperative digital subtraction angiography (DSA) universally, to a strategy of indocyanine green (ICG) videoangiography with DSA on an as-needed basis. We retrospectively evaluated whether the rates of perioperative stroke, unexpected postoperative aneurysm residual, or parent vessel stenosis differed in 100 patients from each era (2002, "DSA era"; 2007, "ICG era"). The clip repositioning rate for neck residual or parent vessel stenosis did not differ significantly between the two eras. There were no differences in the rate of perioperative stroke or rate of false-negative studies. The per-patient cost of intraoperative imaging within the DSA era was significantly higher than in the ICG era. The replacement of routine intraoperative DSA with ICG videoangiography and selective intraoperative DSA in cerebrovascular aneurysm surgery is safe and effective.

Continued concern about parent vessel steno-occlusive progression with Onyx HD-500 and the utility of quantitative magnetic resonance imaging in serial assessment.

BACKGROUND: Onyx HD-500 is a liquid embolic used to treat intracranial aneurysms. OBJECTIVE: To determine the incidence of parent vessel stenosis and the management strategy for these patients. METHODS: Medical records of patients treated with Onyx HD-500 between 2008 and 2011 were retrospectively reviewed. Clinical and radiographic evaluations were assessed. Quantitative magnetic resonance angiography and NOVA (VasSol, Chicago, Illinois) images were reviewed for patients in whom these examinations were acquired. RESULTS: Seventeen patients underwent treatment of unruptured internal carotid artery aneurysms. Three patients (17.6%) developed visual symptoms after the procedure: 2 permanent and 1 transient. Four patients (23.5%) developed delayed internal carotid artery stenosis at the 6- to 8-month follow-up angiography, despite a standard antiplatelet regimen with confirmed sensitivities to aspirin and clopidogrel. Quantitative magnetic resonance angiography was obtained in all patients with stenosis to guide treatment. One patient progressed to complete but asymptomatic internal carotid artery occlusion. The second and third patients had asymptomatic stenosis of 40% and 70%, respectively, both of which resolved on follow-up angiography. The fourth patient developed critical stenosis distal to the aneurysm neck. Quantitative magnetic resonance angiography demonstrated adequate flow in the first 3 patients and decreased flow in the fourth patient, necessitating angioplasty and stenting. Prolonged dual antiplatelet regimens were continued in 2 of the 4 patients, 1 with progression of stenosis and 1 with improvement of stenosis. CONCLUSION: We observed a higher rate of parent vessel steno-occlusive progression after aneurysm embolization with Onyx HD-500 than reported in the literature, despite overall low morbidity. Quantitative vessel flow imaging was useful in subsequent medical management and decision making to perform therapeutic angioplasty/stenting to preserve flow.