Simulation of the natural history of cerebral aneurysms based on data from the International Study of Unruptured Intracranial Aneurysms

Current understanding of macrophages in intracranial aneurysm: relevant etiological manifestations, signaling modulation and therapeutic strategies

Macrophages activation and inflammatory response play crucial roles in intracranial aneurysm (IA) formation and progression. The outcome of ruptured IA is considerably poor, and the mechanisms that trigger IA progression and rupture remain to be clarified, thereby developing effective therapy to prevent subarachnoid hemorrhage (SAH) become difficult. Recently, climbing evidences have been expanding our understanding of the macrophages relevant IA pathogenesis, such as immune cells population, inflammatory activation, intra-/inter-cellular signaling transductions and drug administration responses. Crosstalk between macrophages disorder, inflammation and cellular signaling transduction aggravates the devastating consequences of IA. Illustrating the pros and cons mechanisms of macrophages in IA progression are expected to achieve more efficient treatment interventions. In this review, we summarized the current advanced knowledge of macrophages activation, infiltration, polarization and inflammatory responses in IA occurrence and development, as well as the most relevant NF-κB, signal transducer and activator of transcription 1 (STAT1) and Toll-Like Receptor 4 (TLR4) regulatory signaling modulation. The understanding of macrophages regulatory mechanisms is important for IA patients' clinical outcomes. Gaining insight into the macrophages regulation potentially contributes to more precise IA interventions and will also greatly facilitate the development of novel medical therapy.

Risk of Rupture After Intracranial Aneurysm Growth

Importance

Unruptured intracranial aneurysms not undergoing preventive endovascular or neurosurgical treatment are often monitored radiologically to detect aneurysm growth, which is associated with an increase in risk of rupture. However, the absolute risk of aneurysm rupture after detection of growth remains unclear.

Objective

To determine the absolute risk of rupture of an aneurysm after detection of growth during follow-up and to develop a prediction model for rupture.

Design, Setting, and Participants

Individual patient data were obtained from 15 international cohorts. Patients 18 years and older who had follow-up imaging for at least 1 untreated unruptured intracranial aneurysm with growth detected at follow-up imaging and with 1 day or longer of follow-up after growth were included. Fusiform or arteriovenous malformation-related aneurysms were excluded. Of the 5166 eligible patients who had follow-up imaging for intracranial aneurysms, 4827 were excluded because no aneurysm growth was detected, and 27 were excluded because they had less than 1 day follow-up after detection of growth.

Exposures

All included aneurysms had growth, defined as 1 mm or greater increase in 1 direction at follow-up imaging.

Main Outcomes and Measures

The primary outcome was aneurysm rupture. The absolute risk of rupture was measured with the Kaplan-Meier estimate at 3 time points (6 months, 1 year, and 2 years) after initial growth. Cox proportional hazards regression was used to identify predictors of rupture after growth detection.

Results

A total of 312 patients were included (223 [71%] were women; mean [SD] age, 61 [12] years) with 329 aneurysms with growth. During 864 aneurysm-years of follow-up, 25 (7.6%) of these aneurysms ruptured. The absolute risk of rupture after growth was 2.9% (95% CI, 0.9-4.9) at 6 months, 4.3% (95% CI, 1.9-6.7) at 1 year, and 6.0% (95% CI, 2.9-9.1) at 2 years. In multivariable analyses, predictors of rupture were size (7 mm or larger hazard ratio, 3.1; 95% CI, 1.4-7.2), shape (irregular hazard ratio, 2.9; 95% CI, 1.3-6.5), and site (middle cerebral artery hazard ratio, 3.6; 95% CI, 0.8-16.3; anterior cerebral artery, posterior communicating artery, or posterior circulation hazard ratio, 2.8; 95% CI, 0.6-13.0). In the triple-S (size, site, shape) prediction model, the 1-year risk of rupture ranged from 2.1% to 10.6%.

Conclusion and Relevance

Within 1 year after growth detection, rupture occurred in approximately 1 of 25 aneurysms. The triple-S risk prediction model can be used to estimate absolute risk of rupture for the initial period after detection of growth.

Microsurgery of Giant Intracranial Aneurysm: A Single Institution Outcome Study

Background

Giant intracranial aneurysms (GIAs) are treacherous lesions and in spite of the many advances, endovascular therapy (EVT) of GIAs is challenging.

Objective

A retrospective analysis of our results with microsurgery of GIAs is presented to examine the role of microsurgery in the current trend of EVT.

Materials and Methods

Between 1996 and 2019, 134 patients with 147 GIAs had microsurgery by the senior author in a single institute. The medical and imaging records for all the patients were reviewed. The patient outcome was determined by modified Rankin scale (mRS); ≤3 was considered as a good outcome. Statistical analysis was done using the SPSS program and odds ratios and their 95% confidence intervals were computed; a probability value of < 0.05 was considered significant.

Results

There were 123 aneurysms (83.7%) in the anterior circulation and 24 aneurysms (16.3%) in the posterior circulation. Overall 103 out of 134 (76.8%) patients had a good outcome postoperatively. Good preoperative mRS score (≤3) had an overall good prognosis in the postoperative period and was statistically significant (P = 0.000, odds ratio: 0.036, 95% CI: 0.008-0.171). Presence of subarachnoid hemorrhage (SAH) was also statistically significant for good outcome (P = 0.04, odds ratio: 2.898, 95% CI: 1.051-7.991), but age was not a significant prognostic factor. Mortality within 30 days of treatment was 4.47%.

Conclusion

GIAs need treatment because of their dismal natural history. Results of microsurgical treatment by a single surgeon of the large current series compare well with the results of EVT and justifies pursuing microsurgery for GIAs.

Neuroaxial Infantile Hemangiomas: Imaging Manifestations and Association with Hemangioma Syndromes

BACKGROUND AND PURPOSE

Infantile hemangiomas are common lesions in the pediatric population; in rare cases, an infantile hemangioma can be detected along the neural axis. The purposes of our study included determination of the incidence, location, and imaging appearance of neuroaxial infantile hemangiomas and their syndromic association. We also assessed additional features of cerebral and cardiovascular anomalies that may be associated with neuroaxial lesions.

MATERIALS AND METHODS

A retrospective cohort study was performed, searching the radiology database for patients with segmental infantile hemangiomas referred for assessment of possible hemangioma syndromes. We retrospectively reviewed brain and spine MR imaging studies, with particular attention paid to neuroaxial vascular lesions, as well as the relevant clinical data. Neuroaxial hemangioma imaging findings were described, and comparison of segmental cutaneous infantile hemangioma location with the imaging findings was performed in patients with confirmed hemangioma syndromes and in patients with isolated skin infantile hemangioma.

RESULTS

Ninety-five patients with segmental infantile hemangioma were included in the study, 42 of whom had a hemangioma syndrome; of those, 41 had posterior fossa brain malformations, hemangioma, arterial lesions, cardiac abnormalities, and eye abnormalities (PHACE) syndrome and 1 had diffuse neonatal hemangiomatosis. Neuroaxial involvement was detected in 20/42 patients (48%) with hemangioma syndromes and in no subjects with isolated segmental infantile hemangioma (P < .001). The most common intracranial hemangioma location was within the ipsilateral internal auditory canal (83%).

CONCLUSIONS

Many pediatric patients with segmental infantile hemangioma in the setting of hemangioma syndromes, especially those with PHACE, had neuroaxial hemangiomas. This finding may potentially lead to requiring additional clinical evaluation and management of these patients.

Intracranial Capillary Hemangioma in the Posterior Fossa of an Adult Male

Intracranial capillary hemangioma (ICH) is a rare entity, with approximately 24 reported cases in the literature. There are only three reported cases of ICH in an adult male. In this case report, we describe the fourth documented case of ICH in an adult male and, to the best of our knowledge, the first ever documented case of ICH in the posterior fossa of an adult male. We also discuss its imaging appearance and differential diagnosis.

Age of collagen in intracranial saccular aneurysms

BACKGROUND AND PURPOSE

The chronological development and natural history of cerebral aneurysms (CAs) remain incompletely understood. We used (14)C birth dating of a main constituent of CAs, that is, collagen type I, as an indicator for biosynthesis and turnover of collagen in CAs in relation to human cerebral arteries to investigate this further.

METHODS

Forty-six ruptured and unruptured CA samples from 43 patients and 10 cadaveric human cerebral arteries were obtained. The age of collagen, extracted and purified from excised CAs, was estimated using (14)C birth dating and correlated with CA and patient characteristics, including the history of risk factors associated with atherosclerosis and potentially aneurysm growth and rupture.

RESULTS

Nearly all CA samples contained collagen type I, which was <5 years old, irrespective of patient age, aneurysm size, morphology, or rupture status. However, CAs from patients with a history of risk factors (smoking or hypertension) contained significantly younger collagen than CAs from patients with no risk factors (mean, 1.6±1.2 versus 3.9±3.3 years, respectively; P=0.012). CAs and cerebral arteries did not share a dominant structural protein, such as collagen type I, which would allow comparison of their collagen turnover.

CONCLUSIONS

The abundant amount of relatively young collagen type I in CAs suggests that there is an ongoing collagen remodeling in aneurysms, which is significantly more rapid in patients with risk factors. These findings challenge the concept that CAs are present for decades and that they undergo only sporadic episodes of structural change.

Risk perception of unruptured intracranial aneurysms

OBJECT

Recent prospective studies have shown that the rupture rate of small unruptured intracranial aneurysms is very low. However, awareness of harboring an aneurysm often provokes anxiety and depression, which may reduce the quality of life (QOL).

METHODS

This cross-sectional study enrolled 52 patients who had previously been notified of the presence of untreated unruptured aneurysms. A Markov model was constructed to simulate the natural history over time, and the age- and size-specific loss of quality-adjusted life year (QALY) caused by the aneurysms was calculated. Preference-based subjective QALY losses (PSG and PTTO) were assessed using the standard gamble (SG) and time trade-off (TTO) according to patient's own perceptions.

RESULTS

Calculated theoretical QALY losses were relatively small with median values of 0.4 years (interquartile range [IQR] 0.1-1.0 years) and 1.9 % (IQR 1.1-3.7 %) of expected lifetime. The median values of PSG and PTTO were 10.0 % (IQR 5.0-14.3 %) and 19.5 % (IQR 9.0-25.0 %), respectively. Although theoretical QALY losses were smaller in the patients with small aneurysms (<5 mm) than in patients with medium ∼ large aneurysms (≥5 mm), the PSG and PTTO were almost the same in both groups. The discrepancy between theoretical and subjective QALY losses was prominent in patients with small aneurysms.

CONCLUSIONS

Notification of unruptured aneurysms exerts a significant psychological burden, and excessively reduces the QOL relative to the theoretical risks. The present study suggests that neurosurgeons should reconsider the method used to inform patients of small lesions with low risk of severe consequences.

Cerebral aneurysms: formation, progression, and developmental chronology

The prevalence of unruptured intracranial aneurysms (UIAs) in the general population is up to 3%. Existing epidemiological data suggests that only a small fraction of UIAs progress towards rupture over the lifetime of an individual, but the surrogates for subsequent rupture and the natural history of UIAs are discussed very controversially at present. In case of rupture of an UIA, the case fatality is up to 50%, which therefore continues to stimulate interest in the pathogenesis of cerebral aneurysm formation and progression. Actual data on the chronological development of cerebral aneurysm has been especially difficult to obtain and, until recently, the existing knowledge in this respect is mainly derived from animal or mathematical models or short-term observational studies. Here, we review the current data on cerebral aneurysm formation and progression as well as a novel approach to investigate the developmental chronology of cerebral aneurysms.

Carotid siphon geometry and variants of the circle of Willis in the origin of carotid aneurysms

This study evaluated anatomical variants in the carotid siphon and of the circle of Willis in patients with aneurysms. We performed a retrospective analysis of cerebral angiographies. The Control Group was composed of patients without aneurysms. Posterior communicating artery (PcomA) aneurysms were more common in women (p<0.05), and the anterior communicating artery (AcomA) aneurysms in men (p<0.1). The incidence of fetal-type PcomA was higher in cases with co-occurring PcomA aneurysm (24 versus 8%, p<0.05). Patients with AcomA aneurysm had higher incidence of A1 hypoplasia (p<0.0001, OR=32.13, 95%CI 12.95-79.71) and lower frequency of fetal-type PcomA compared to their control counterparts (p=0.0125). The angle of carotid siphon was narrower in patients with PcomA aneurysm (27.3±19.1 versus 34.8±22.6, p=0.028). In conclusion, a narrower carotid siphon or the presence of fetal-type PcomA or A1 hypoplasia may cause hemodynamic stress, thereby promoting the formation of aneurysms in susceptible individuals.

Estimated low risk of rupture of small-sized unruptured intracranial aneurysms (UIAs) in relation to intracranial aneurysms in patients with subarachnoid haemorrhage

OBJECTIVE

International guidelines for the management of unruptured intracranial aneurysms (UIAs) recommend observation in aneurysms <10 mm due to the estimated low risk of rupture. The aim of our study was analyse the data of recently treated patients with ruptured cerebral aneurysms with the special focus on size and configuration in view of the frequency scale in a daily routine setting.

METHODS

We reviewed the data of all patients with aneurysmal subarachnoid haemorrhage (SAH) during the last 24 months at our institution. Configuration and size of the aneurysms were measured. Clinical data were collected using the following classifications for analysis: Hunt and Hess (H&H), modified Rankin Scale (mRS) and Fisher classification.

RESULTS

Data of 135 patients with aneurysmal SAH (98 women, 37 men; ratio 2.6:1) were analysed. Analysis showed that 19 aneurysms (14 %) were >10 mm (mean size, 19.2 mm) and 116 aneurysms (85.9 %) <10 mm (mean size, 6.2 mm). In total, 112 were categorised as berry-like configured aneurysms (n = 113 <10 mm, n = 3 >10 mm), 18 as multi-lobar (n = 16 <10 mm, n = 2 >10 mm) and 5 as fusiform (n = 4 <10 mm, n = 1, >10 mm).

CONCLUSION

Since the results of our study showed that the majority of the aneurysms are <10 mm (mean, 6.2 mm), it is justified to challenge the recommendations of the international guidelines in a daily routine setting. We believe that the published data are not convincing enough to play a guidance role in daily routine. Due to improving surgical and endovascular techniques with satisfying results and the high number of ruptured small aneurysms, we believe a change in attitude in management of small-sized aneurysms is needed. Further diagnostic models are needed to determine the risk of rupture of intracranial aneurysms properly to obtain adequate treatment for UIAs.

Simulation of intra-aneurysmal blood flow by different numerical methods

The occlusional performance of sole endoluminal stenting of intracranial aneurysms is controversially discussed in the literature. Simulation of blood flow has been studied to shed light on possible causal attributions. The outcome, however, largely depends on the numerical method and various free parameters. The present study is therefore conducted to find ways to define parameters and efficiently explore the huge parameter space with finite element methods (FEMs) and lattice Boltzmann methods (LBMs). The goal is to identify both the impact of different parameters on the results of computational fluid dynamics (CFD) and their advantages and disadvantages. CFD is applied to assess flow and aneurysmal vorticity in 2D and 3D models. To assess and compare initial simulation results, simplified 2D and 3D models based on key features of real geometries and medical expert knowledge were used. A result obtained from this analysis indicates that a combined use of the different numerical methods, LBM for fast exploration and FEM for a more in-depth look, may result in a better understanding of blood flow and may also lead to more accurate information about factors that influence conditions for stenting of intracranial aneurysms.

Dural infantile hemangioma masquerading as a skull vault lesion

We describe a case of intracranial dural IH initially diagnosed as a primary skull vault lesion hemangioma due to associated focal hyperostosis. Histopathologic examination of the dural component confirmed IH. The case is discussed in the context of IH within the neural axis.

Analysis of Nonmodifiable Risk Factors for Intracranial Aneurysm Rupture in a Large, Retrospective Cohort

Background:

The risk factors predictive of intracranial aneurysm rupture remain incompletely defined.

Objective:

To examine the association between various nonmodifiable risk factors and aneurysm rupture in a large cohort of patients evaluated at a single institution.

Methods:

A retrospective analysis of patients admitted to a cerebrovascular facility between January 2006 and 2010 with a primary diagnosis of cerebral aneurysm. Aneurysms were divided into 2 groups: unruptured or ruptured. The dome diameter, aspect ratio (AR), location, sidedness, neck morphology, and multiplicity were entered into a central database. A full model was constructed, and a systematic removal of the least significant variables was performed in a sequential fashion until only those variables reaching significance remained.

Results:

We identified 2347 patients harboring 5134 individual aneurysms, of which 34.90% were ruptured and 65.09% were unruptured. On admission, 25.89% of aneurysms with a dome diameter &lt;10 mm and 58.33% of aneurysms with a dome &gt;10 mm were ruptured (P &lt; .001). Of aneurysms with an AR &gt;1.6, 52.44% presented following a rupture (P &lt; .001). The highest incidence of rupture (69.21%) was observed in aneurysms with an AR &gt;1.6, dome diameter &lt;10 mm, and a deviated neck. Deviated neck-type aneurysms had a significantly greater incidence of rupture than classical necktype aneurysms (P &lt; .001).

Conclusion:

An AR &gt;1.6, dome diameter &gt;10 mm, a deviated neck, and right-sidedness are independently associated with aneurysm rupture.

Surgical results of unruptured intracranial aneurysms in the elderly : single center experience in the past ten years

OBJECTIVE

As medical advances have increased life expectancy, it has become imperative to develop specific treatment strategies for intracranial aneurysms in the elderly. We therefore analyzed the clinical characteristics and outcomes of the treatment of unruptured intracranial aneurysms in patients older than 70 years.

METHODS

We retrospectively reviewed the medical records and results of neuroimaging modalities on 54 aneurysms of 48 consecutive patients with unruptured intracranial aneurysms. (mean±SD age, 72.11±1.96 years; range, 70-78 years) who underwent surgical clipping over 10 years (May 1999 to June 2010).

RESULTS

Of the 54 aneurysms, 22 were located in the internal carotid artery, 19 in the middle cerebral artery, 12 in the anterior cerebral artery, and 1 in the superior cerebellar artery. Six patients had multiple aneurysms. Aneurysm size ranged from 3 mm to 17 mm (mean±SD, 6.82±3.07 mm). Fifty of the 54 aneurysms (92.6%) were completely clipped. Three-month outcomes were excellent in 50 (92.6%) aneurysms and good and poor in 2 each (3.7%), with 1 death (2.0%). Procedure-related complications occurred in 7 aneurysms (13.0%), with 2 (3.7%) resulting in permanent neurological deficits, including death. No postoperative subarachnoid hemorrhage occurred during follow-up. The cumulative rates of stroke- or death-free survival at 5 and 10 years were 100% and 78%, respectively.

CONCLUSION

Surgical clipping of unruptured intracranial aneurysms in elderly group could get it as a favorable outcome in well selected cases.

Relationship of Growth to Aneurysm Rupture in Asymptomatic Aneurysms ≤ 7 mm: A Systematic Analysis of the Literature

BACKGROUND:

The apparent paradox of natural history data suggesting low rupture risk of small asymptomatic aneurysms and the median size of aneurysm rupture remains unexplained. Aneurysm growth rates and their potential relationship with rupture risk have not been well examined in natural history studies.

OBJECTIVE:

To examine the question of whether small asymptomatic aneurysms ≤ 7 mm that are followed up over time rupture and to determine the relationship between aneurysm growth and rupture.

METHODS:

We reviewed all publications on unruptured aneurysms published from 1966 to 2009. We then selected all aneurysms ≤ 7 mm for which measurements were reported for at least 2 time points and for which initial asymptomatic status and ultimate outcome (rupture vs unruptured) were reported. Using the Mann-Whitney U test, we compared absolute diameter annual growth rate.

RESULTS:

Our search retrieved 64 aneurysms. Thirty aneurysms ruptured during follow-up, of which 27 were enlarged before rupture (90%). Thirty-four aneurysms did not rupture, of which 24 enlarged during follow-up (71%). There was a statistically significant trend toward larger absolute diameter growth for ruptured aneurysms vs unruptured aneurysms (3.89 ± 2.34 vs 1.79 ± 1.02 mm; P &lt; .001), respectively. Annual growth rates for aneurysms for the 2 groups, however, were not statistically different (27.46 ± 18.76 vs 32.00 ± 29.30; P = .92).

CONCLUSION:

Small aneurysms are prone to growth and rupture. Aneurysm rupture is more likely to occur in aneurysms with larger absolute diameter growth, but rupture can also occur in the absence of growth. The annual growth rate in both groups suggests that rate of growth of aneurysms is highly variable and unpredictable, justifying treatment or close diagnostic follow-up.

The small “surgical aneurysm” at the basilar apex

Object

Because the risks are reduced, larger basilar apex aneurysms are usually treated endovascularly instead of with surgery. However, small basilar apex aneurysms are more common and an unfavorable shape may prevent definitive endovascular treatment. The goal of this study was to reevaluate the outcome of traditional surgery for small unruptured basilar apex aneurysms as an alternative to the currently more accepted endovascular treatment.

Methods

The authors reviewed clinical data obtained in 21 patients who underwent surgery between 2000 and 2007 for unruptured basilar apex aneurysms < 7 mm.

Results

The median age of the 21 patients was 52 years (range 29–74 years). All patients experienced a good outcome. Two patients harbored a small residual aneurysm (> 95% occlusion). Eight patients (38%) suffered a temporary third nerve paresis, which resolved in all cases.

Conclusions

Surgical clip ligation remains an excellent treatment for small basilar apex aneurysms. The treatment is definitive and in experienced hands is associated with a low risk.

Congenital tumors of the central nervous system

Congenital tumors of the central nervous system (CNS) are often arbitrarily divided into "definitely congenital" (present or producing symptoms at birth), "probably congenital" (present or producing symptoms within the first week of life), and "possibly congenital" (present or producing symptoms within the first 6 months of life). They represent less than 2% of all childhood brain tumors. The clinical features of newborns include an enlarged head circumference, associated hydrocephalus, and asymmetric skull growth. At birth, a large head or a tense fontanel is the presenting sign in up to 85% of patients. Neurological symptoms as initial symptoms are comparatively rare. The prenatal diagnosis of congenital CNS tumors, while based on ultrasonography, has significantly benefited from the introduction of prenatal magnetic resonance imaging studies. Teratomas constitute about one third to one half of these tumors and are the most common neonatal brain tumor. They are often immature because of primitive neural elements and, rarely, a component of mixed malignant germ cell tumors. Other tumors include astrocytomas, choroid plexus papilloma, primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumors, and medulloblastomas. Less common histologies include craniopharyngiomas and ependymomas. There is a strong predilection for supratentorial locations, different from tumors of infants and children. Differential diagnoses include spontaneous intracranial hemorrhage that can occur in the presence of coagulation factor deficiency or underlying vascular malformations, and congenital brain malformations, especially giant heterotopia. The prognosis for patients with congenital tumors is generally poor, usually because of the massive size of the tumor. However, tumors can be resected successfully if they are small and favorably located. The most favorable outcomes are achieved with choroid plexus tumors, where aggressive surgical treatment leads to disease-free survival.

Alternative option in the treatment of very small ruptured intracranial aneurysms

BACKGROUND

To evaluate the safety and protective effect of relative undersized coil with loose coil core in the clinical dilemma condition--very small (43.0 mm) ruptured intracranial aneurysm.

METHODS

We studied 12 patients (4 men, 8 women) who had suffered from acute ruptured small intracranial aneurysms (2-3 mm in size, with SAH presentation). All subjects underwent a single coil embolization procedure. An undersized coil (equivalent to the neck size or 0.5 mm smaller than the aneurysm diameter) was chosen as the embolizer. Based on the postembolization angiogram, subjects were divided into 2 groups. One was labeled as the initial complete obliteration group (NR) and the other as the incomplete obliteration group (SR). Fisher exact test and the Wilcoxon rank sum test were used to for statistical analysis.

RESULTS

The technical success rate was 100% without any procedure-related complication. The follow-up interval ranged from 6 to 32 months. No episode of rebleeding or coil migration could be defined in the admissive and following period. Loose coil core were seen in all patients. The total recurrent rate was 8.3% (1/12); only one patient suffered from recurrent lesion in SR group.

CONCLUSION

The preliminary result showed that under-sized coil packing with loose coil core could provide the protective effect and prevent from further rebleeding for very small ruptured aneurysms. It should be considered as an alternative option in the treatment of acute ruptured very small aneurysms when other conventional strategies are not feasible.

Influence of intracranial aneurysm-to-parent vessel size ratio on hemodynamics and implication for rupture: results from a virtual experimental study

OBJECTIVE

The effectiveness of intracranial aneurysm (IA) size as a predictor for rupture has been debated. We recently performed a retrospective analysis of IA morphology and found that a new index, namely, aneurysm-to-parent vessel size ratio (SR), was strongly correlated with IA rupture, with 77% of ruptured IAs showing an SR of more than 2, and 83% of unruptured IAs showing an SR of 2 or less. As hemodynamics have been implicated in both IA development and rupture, we examine how varying SR influences intra-aneurysmal hemodynamics.

METHODS

One sidewall and 1 terminal IA were virtually reconstructed from patient 3-dimensional angiographic images. In 2 independent in silico experiments, the SR was varied from 1.0 to 3.5 by virtually changing either aneurysm size or vessel diameter while keeping the other parameter constant. Pulsatile computational fluid dynamics simulations were performed on each model for hemodynamics analysis.

RESULTS

Low SR (</=2) aneurysm morphology consistently demonstrated simple flow patterns with a single intra-aneurysmal vortex, whereas higher SR (>2) aneurysm morphology presented multiple vortices and complex flow patterns. The aneurysm luminal area that was exposed to low wall shear stress increased with increasing SR. Complex flow, multiple vortices, and low aneurysmal wall shear stress have been associated with ruptured IAs in previous studies.

CONCLUSION

Higher SR, irrespective of aneurysm type and absolute aneurysm or vessel size, gives rise to flow patterns typically observed in ruptured IAs. These results provide hemodynamic support for the existing correlation of SR with rupture risk.

Growth rate and rupture rate of unruptured intracranial aneurysms: a population approach

Background

Understanding aneurysm growth rate allows us to predict not only the current rupture risk, but also accumulated rupture risk in the future. However, determining growth rate of unruptured intracranial aneurysms often requires follow-up of patients for a long period of time so that significant growth can be observed and measured. We investigate a relationship between growth rate and rupture rate and develop a theoretical model that can predict average behavior of unruptured intracranial aneurysms based on existing clinical data.

Methods

A mathematical model is developed that links growth rate and rupture rate. This model assumes a stable aneurysm size distribution so the number of aneurysm ruptures is balanced by the growth of aneurysms. Annual growth rates and growth profiles are calculated from a hypothetical size distribution and data from a previous clinical study.

Results

Our model predicts a growth rate of 0.34–1.63 mm/yr for three different growth models when the rupture rate at 10 mm is 1%. The growth rate is 0.56–0.65 mm/yr if annual rupture rate averaged over all aneurysm sizes is assumed to be 2%. The peak of aneurysm size distribution coincides with a period of slow growth between 5 mm and 8 mm.

Conclusion

This mathematical model can be used to predict aneurysm growth rate, and the results are consistent with previous clinical studies. Predictions from both hypothetical and clinical cases agree very well. This model explains why some aneurysms may grow into a stable size and remain so without rupture.

Infantile hemangiomas involving the neuraxis: clinical and imaging findings

BACKGROUND AND PURPOSE

The neuroradiology and neurosurgery literature is replete with references to "hemangioma" involving the central nervous system (CNS). However, the number of cases of true infantile hemangiomas in the CNS reported to date is 15. Our purpose was to delineate the definition of infantile hemangiomas, determine their prevalence in the neuraxis, and describe their imaging characteristics and associations in this location.

MATERIALS AND METHODS

We reviewed our Vascular Anomalies Center data base from 1999 through May 2008 to assess the prevalence of intracranial or intraspinal involvement within the total cohort of infantile hemangiomas. Fifteen patients were identified with infantile hemangiomas that involved the neuraxis. Two board-certified neuroradiologists reviewed the available imaging of these 15 patients, and a board-certified pathologist reviewed the available histopathology. Clinical records of all 15 patients were reviewed to identify the type of treatment and the treatment response.

RESULTS

Of the 1454 patients listed with infantile hemangioma, 15 (approximately 1.0%) had involvement of the CNS. Eight patients had intracranial infantile hemangioma, 6 had intraspinal hemangioma, and 1 had both. In most instances, there was continuous extension into the neuraxis from an extracranial or extraspinal lesion. There were no cases of a CNS hemangioma without an accompanying extra-CNS tumor. Two patients had findings consistent with posterior fossa anomalies, cervicofacial hemangioma, arterial anomalies, cardiac defects, ocular abnormalities, and associated sternal or ventral defect. Of note, there were no brain or spinal parenchymal signal-intensity abnormalities, and there was no evidence of parenchymal invasion.

CONCLUSIONS

CNS involvement by infantile hemangiomas is an unusual occurrence, which, when recognized, can help optimize patient management.

Clipping of very large or giant unruptured intracranial aneurysms in the anterior circulation: an outcome study

Object

Patients with very large or giant unruptured intracranial aneurysms present with ischemic stroke and progressive disability. The aneurysm rupture risk in these patients is extreme—up to 50% in 5 years. In this study the authors investigated the outcome of surgical treatment for these very large aneurysms in the anterior circulation.

Methods

Clinical data on 62 patients who underwent surgery for unruptured aneurysms (20–60 mm) between 1998 and 2006 were reviewed.

Results

Complete aneurysm occlusion (100%) was achieved in 90% of cases, near complete occlusion (90–99%) in 5%. The surgical risk in patients younger than 50 years of age was 8% (Glasgow Outcome Scale score of 1 or 3 within 1 year after surgery). In older patients, the risk increased with advancing age.

Conclusions

The treatment of very large or giant unruptured intracranial aneurysms is hazardous and complex and thus best performed only at major cerebrovascular centers with an experienced team of neurosurgeons, interventional neuroradiologists, neurologists, and neuroanesthesiologists. Surgery, with acceptable risks and excellent occlusion rates, is typically the treatment of choice in patients younger than 50 years of age. In older patients, the benefits of endovascular treatment versus surgery versus no treatment must be carefully weighed individually. Minimizing temporary occlusion and the consequent use of intraoperative angiography may help reduce surgical complications.

Growth rates of intracranial aneurysms: exploring constancy

OBJECT

The annual rate of rupture of intracranial aneurysms is often assumed to be constant, but it is unknown whether this assumption is true. Recent case reports have suggested that aneurysms grow fast in a short period of time. The authors of the present report investigated the plausibility of a constant growth rate for intracranial aneurysms.

METHODS

Assuming a constant aneurysm growth rate within an individual and varying rates between individuals, a hypothetical cohort was simulated. Individuals with high growth rates will display aneurysm formation and rupture at a young age; such persons disappear early from the hypothetical cohort. As a result the mean lesion growth rate varies over time. In hypothetical cohorts with different initial mean growth rates, the authors calculated age-specific incidence rates (per 100,000 person-years) of subarachnoid hemorrhage and compared these rates with population-based data on the incidence of subarachnoid hemorrhage (per 100,000 person-years).

RESULTS

A hypothetical cohort with a mean initial growth rate of 0.18 mm/year reproduced most closely the incidence rates observed in the population. However, even for this most plausible hypothetical cohort, age-specific incidence rates in the model differed substantially and statistically significantly from those observed in the population.

CONCLUSIONS

Based on the results of this study, it is unlikely that intracranial aneurysms in general grow at a constant time-independent rate. The authors hypothesized that the actual growth process is irregular and discontinuous, which results in periods with and without aneurysm growth and with high and low risks of rupture.

The merits of endovascular coil surgery for patients with unruptured intracranial aneurysms

OBJECTIVE

The purpose of this study was to report the morbidity, mortality, angiographic results, and merits of elective coiling of unruptured intracranial aneurysms.

METHODS

Ninety-six unruptured aneurysms in 92 patients were electively treated with detachable coils. Eighty-one of these aneurysms were located in the anterior circulation, and 15 were located in the posterior circulation. Thirty-six aneurysms were treated in the presence of previously ruptured aneurysms that had already undergone operation. Nine unruptured aneurysms presented with symptoms of mass effect. The remaining 51 aneurysms were incidentally discovered in patients with other cerebral diseases and in individuals undergoing routine health maintenance. Angiographic and clinical outcomes and procedure-related complications were analyzed.

RESULTS

Eight procedure-related untoward events (8.3%) occurred during surgery or within procedure-related hospitalization, including thromboembolism, sac perforation, and coil migration. Permanent procedural morbidity was 2.2% ; there was no mortality. Complete occlusion was achieved in 73 (76%) aneurysms, neck remnant occlusion in 18 (18.7%) aneurysms, and incomplete occlusion in five (5.2%) aneurysms. Recanalization occurred in 8 (15.4%) of 52 coiled aneurysms that were available for follow-up conventional angiography or magnetic resonance angiography over a mean period of 13.3 months. No ruptures occurred during the follow-up period (12-79 months).

CONCLUSION

Endovascular coil surgery for patients with unruptured intracranial aneurysms is characterized by low procedural mortality and morbidity and has advantages in patients with poor general health, cerebral infarction, posterior circulation aneurysms, aneurysms of the proximal internal cerebral artery, and unruptured aneurysms associated with ruptured aneurysm. For the management of unruptured aneurysms, endovascular coil surgery is considered an attractive alterative option.