Anatomical diversity amongst cerebellar AVMs calls for a classification that is intuitive and surgically informative. Selection tools like the Spetzler-Martin grading system are designed to work best with cerebral AVMs, but have shortcomings with cerebellar AVMs.
To define subtypes of cerebellar AVMs that clarify anatomy and surgical management, determine results according to subtypes, and compare predictive accuracies of Spetzler-Martin and supplementary systems.
From a consecutive surgical series of 500 patients, 60 had cerebellar AVMs, 39 had brain stem AVMs and were excluded, and 401 had cerebral AVMs.
Cerebellar AVM subtypes were: 18 vermian, 13 suboccipital, 12 tentorial, 12 petrosal, and 5 tonsillar. Patients with tonsillar and tentorial AVMs fared best. Cerebellar AVMs presented with hemorrhage more than cerebral AVMs (p<0.001). Cerebellar AVMs were more likely to drain deep (p=0.036) and less likely eloquent (p<0.001). The predictive accuracy of supplementary grade was better than that of Spetzler-Martin grade with cerebellar AVMs (areas under the ROC curve 0.74 and 0.59, respectively). The predictive accuracy of the supplementary system was consistent for cerebral and cerebellar AVMs, whereas that of the Spetzler-Martin system was greater with cerebral AVMs.
Patients with cerebellar AVMs present with hemorrhage more than patients with cerebral AVMs, justifying an aggressive treatment posture. The supplementary system is better than the Spetzler-Martin system at predicting outcomes after cerebellar AVM resection. Key components of the Spetzler-Martin system, like venous drainage and eloquence, are distorted by cerebellar anatomy in ways that components of the supplementary system are not.
arteriovenous malformation; cerebellum; microsurgical resection; Spetzler Martin grading scale; supplementary grading scale
Vessels in brain arteriovenous malformations (bAVM) are prone to rupture. The underlying pathogenesis is not clear. Hereditary hemorrhagic telangiectasia type 2 (HHT2) patients with activin receptor-like kinase 1 (Alk1) mutation have a higher incidence of bAVM than the general population. We tested the hypothesis that vascular endothelial growth factor (VEGF) impairs vascular integrity in the Alk1-deficient brain through reduction of mural cell-coverage.
Methods and Results
Adult Alk11f/2f mice (loxP sites flanking exons 4-6) and wild-type (WT) mice were injected with 2×107 PFU Ad-Cre and 2×109 genome copies of AAV-VEGF to induce focal homozygous Alk1 deletion (in Alk11f/2f mice) and angiogenesis. Brain vessels were analyzed eight weeks later. Compared to WT mice, the Alk1-deficient brain had more fibrin (99±30×103 pixels/mm2 vs. 40±13×103, P=0.001), iron deposition (508±506 pixels/mm2 vs. 6 ±49, P=0.04), and Iba1+ microglia/macrophage infiltration (888±420 Iba1+ cells/mm2 vs. 240±104 Iba1+, P=0.001) after VEGF stimulation. In the angiogenic foci, the Alk1-deficient brain had more α-SMA- vessels (52±9% vs. 12±7%, P<0.001), fewer vascular associated pericytes (503±179/mm2 vs. 931±115, P<0.001), and reduced PDGFR-β expression (26±9%, P<0.001).
Reduction of mural cell coverage in response to VEGF stimulation is a potential mechanism for the impairment of vessel wall integrity in HHT2-associated bAVM.
brain arteriovenous malformation; activin receptor-like kinase 1; pericyte; iron deposition; PDGFR-β
Abnormal endothelial proliferation and angiogenesis may contribute to brain arteriovenous malformation (BAVM) formation. G protein-coupled receptor 124 (GPR124) mediates embryonic CNS angiogenesis; thus we investigated the association of single nucleotide polymorphisms (SNPs) and haplotypes in GPR124 with risk of BAVM. Ten tagging SNPs spanning 39 kb of GPR124 were genotyped in 195 Caucasian BAVM patients and 243 Caucasian controls. SNP and haplotype association with risk of BAVM was screened using χ2 analysis. Associated variants were further evaluated using multivariable logistic regression, adjusting for age and sex. The minor alleles of 3 GPR124 SNPs adjacent to exon 2 and localized to a 16 kb region of high linkage disequilibrium were associated with reduced risk of BAVM (rs7015566 A, P=0.001; rs7823249 T, P=0.014; rs12676965 C, P=0.007). SNP rs7015566 (intron 1) remained associated after permutation testing (additive model P=0.033). Haplotype analysis revealed a significant overall association (χ2=12.55, 4 df, P=0.014); 2 haplotypes (ATCC, P=0.006 and GGCT, P=0.008) were associated with risk of BAVM. We genotyped a known synonymous SNP (rs16887051) in exon 2, however genotype frequency did not differ between cases and controls. Sequencing of conserved GPR124 regions revealed a novel indel polymorphism in intron 2. Immunohistochemistry confirmed GPR124 expression in the endothelium with no qualitative difference in expression between BAVM cases and controls. SNP rs7015566 mapping to intron 1 of GPR124 was associated with BAVM susceptibility among Caucasians. Future work is focused on investigating this gene region.
Angiogenesis; Genetics; Intracerebral hemorrhage; Risk factor; Vascular malformation
Brain arteriovenous malformations (BAVM) are clusters of abnormal blood vessels, with shunting of blood from the arterial to venous circulation and a high risk of rupture and intracranial hemorrhage. Most BAVMs are sporadic, but also occur in patients with Hereditary Hemorrhagic Telangiectasia, a Mendelian disorder caused by mutations in genes in the transforming growth factor beta (TGFβ) signaling pathway.
To investigate whether copy number variations (CNVs) contribute to risk of sporadic BAVM, we performed a genome-wide association study in 371 sporadic BAVM cases and 563 healthy controls, all Caucasian. Cases and controls were genotyped using the Affymetrix 6.0 array. CNVs were called using the PennCNV and Birdsuite algorithms and analyzed via segment-based and gene-based approaches. Common and rare CNVs were evaluated for association with BAVM.
A CNV region on 1p36.13, containing the neuroblastoma breakpoint family, member 1 gene (NBPF1), was significantly enriched with duplications in BAVM cases compared to controls (P = 2.2×10−9); NBPF1 was also significantly associated with BAVM in gene-based analysis using both PennCNV and Birdsuite. We experimentally validated the 1p36.13 duplication; however, the association did not replicate in an independent cohort of 184 sporadic BAVM cases and 182 controls (OR = 0.81, P = 0.8). Rare CNV analysis did not identify genes significantly associated with BAVM.
We did not identify common CNVs associated with sporadic BAVM that replicated in an independent cohort. Replication in larger cohorts is required to elucidate the possible role of common or rare CNVs in BAVM pathogenesis.
Increasing evidence suggests the role of inflammation in enhancing neuronal excitability and contributing to epileptogenesis. Tetracycline-class antibiotics minocycline, doxycycline, and tetracycline have been shown to have anti-apoptotic and anti-inflammatory effects.
We investigated the anti-seizure effects of tetracycline-class antibiotics minocycline, doxycycline, and tetracycline in vivo by using the maximal electric shock (MES), 6Hz (minimal clonic seizure) test, and subcutaneous Metrazol (scMET) models of epilepsy.
Minocycline, doxycycline, and tetracycline showed anticonvulsant effects in abolishing partial seizures in a mouse model of 6Hz seizure test. A dose-dependent effect was found, with ED50 of 170mg/kg for minocycline, 157 mg/kg for doxycycline, and 255 mg/kg for tetracycline with peak onset at 0.5 hours. At high doses, minocycline (250mg/kg) and doxycycline (150mg/kg) also have toxic effects, from motor impairments to respiratory failure and death. These drugs had no effects on the MES and scMET tests.
In three tests of anti-seizure activity, minocycline, doxycycline, and tetracycline were found to be protective in one: the 6Hz seizure model. Our data suggest that minocycline and other tetracycline-class drugs may offer some degree of anticonvulsant effect in the setting of CNS disease trials.
minocycline; doxycycline; tetracycline; seizure; neuroprotection; antiepileptic drugs; anticonvulsant drugs; epilepsy
Our recently proposed point scoring model includes the widely-used Spetzler-Martin (SM)-5 variables, along with age, unruptured presentation, and diffuse border (SM-Supp). Here we evaluate the SM-Supp model performance compared to SM-5, SM-3, and Toronto prediction models using net reclassification index (NRI), which quantifies the correct movement in risk reclassification, and validate the model in an independent dataset.
Bad outcome was defined as worsening between preoperative and final postoperative modified Rankin Scale score. Point scores for each model were used as predictors in logistic regression, and predictions evaluated using NRI at varying thresholds (10–30%) and any threshold (continuous NRI>0). Performance was validated in an independent dataset (n=117).
Net gain in risk reclassification was better using the SM-Supp model over a range of threshold values (NRI=9–25%) and significantly improved overall predictions for outcomes in the development dataset, yielding a continuous NRI of 64% versus SM-5, 67% versus SM-3, and 61% versus Toronto (all P<0.001). In the validation dataset, the SM-Supp model again correctly reclassified a greater proportion of patients versus SM-5 (82%), SM-3 (85%), and Toronto models (69%).
The SM-Supp model demonstrated better discrimination and risk reclassification than several existing models and should be considered for clinical practice to estimate surgical risk in BAVM patients.
receiver operator curve; Modified Rankin Scale; net reclassification
Background and Purpose
The Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) is associated with decreased BDNF secretion and poor outcome after acute neurological injury. We hypothesized that the Met allele is associated with worsening of functional outcome after brain arteriovenous malformation (BAVM) resection.
341 surgically-treated BAVM patients with outcome data were genotyped for Val66Met. Outcome was change in modified Rankin Scale (mRS) preoperatively versus postoperatively, dichotomized into poor (change>0) or good outcome (change≤0). Likelihood ratio test for interactions and logistic regression analysis were performed.
A significant interaction (p=0.03) of Val66Met genotype and hemorrhagic presentation existed; thus, ruptured and unruptured patients were considered separately. The Met allele was associated with increased risk of poor outcome among patients presenting unruptured (OR=2.15, 95% CI=1.02–4.55, p=0.045) but not ruptured (OR=0.54, 95% CI=0.19–1.53, p=0.25), adjusting for covariates.
The Val66Met polymorphism is associated with worsened surgical outcome in unruptured BAVM patients, a group that currently has no good risk predictors. Further studies replicating these findings are needed.
Brain-derived neurotrophic factor; Genetics; Arteriovenous Malformations; Outcomes; Surgery
To quantitatively estimate the relationship between multiplicity of brain arteriovenous malformations (bAVMs) and the diagnosis of hereditary hemorrhagic telangiectasia (HHT).
We combined databases from two large North American bAVM referral centers, including demographics, clinical presentation and angiographic characteristics, and compared HHT patients with non-HHT patients. Logistic regression analysis was performed to quantify the association between bAVM multiplicity and odds of HHT diagnosis. Sensitivity, specificity, positive and negative predictive value (PPV, NPV), and positive and negative likelihood ratios (LR) were calculated to determine accuracy of bAVM multiplicity for screening HHT.
Prevalence of HHT was 2.8% in the combined group. bAVM multiplicity was present in 39% of HHT patients and was highly associated with diagnosis of HHT in univariate (OR=83, 95% CI:40–173, P<0.0001) and multivariable (OR=87, 95% CI: 38–195, P<0.001) models, adjusting for age at presentation (P=0.013), non-symptomatic presentation (P=0.029) and cohort site (P=0.021). bAVM multiplicity alone was associated with high specificity (99.2%, 95%CI: 98.7–99.6%) and NPV (98.3%, 95% CI: 97.6–98.8%), and low sensitivity (39.3%, 95% CI: 26.5–53.2%) and PPV (59.5%, 95% CI: 42.1–75.2%). Positive and negative LR was 51 and 0.61, respectively, for diagnosis of HHT. HHT bAVMs were also more often smaller in size (<3 cm), non-eloquent in location and associated with superficial venous drainage, compared to non-HHT bAVMs.
Multiplicity of bAVMs is highly predictive of the diagnosis of HHT. The presence of multiple bAVMs should alert the clinician to the high probability of HHT and lead to comprehensive investigation for this diagnosis.
arteriovenous malformation; hereditary hemorrhagic telangiectasia; brain
Brain arteriovenous malformation (BAVM), a rare but important cause of intracranial hemorrhage, has increased angiogenesis and inflammation as key components of the nidus of abnormal vessels and stroma that form the resected surgical specimen. Accordingly, vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGFβ) have both been implicated in BAVM pathology for their pro-angiogenic and vascular-regulating roles. The c-terminal fragment of the extracellular matrix component perlecan (domain V, DV) has been shown to be increased and to, via the α5β1 integrin, increase VEGF levels in and around areas of cerebral ischemic injury, another pro-angiogenic condition. We sought to determine whether the concentrations of DV, DV’s proangiogenic receptor α5β1 integrin, or DV’s anti-angiogenic receptor α2β1 integrin are elevated in human BAVM tissue. DV levels were increased in BAVM compared to control brain tissue from epileptic resection, as was α5β1 integrin. Additionally, α5β1 integrin was preferentially increased and localized to endothelial cells compared to α2β1 integrin. VEGF and TGFβ levels were also increased in BAVM compared to control tissue. Furthermore, increases in all components were strongly correlated. Excessive generation of pro-angiogenic DV in BAVM suggests that DV may participate in its pathology and may represent a future therapeutic target.
Arteriovenous Malformation; AVM
Inflammation cell infiltration and cytokine expression are seen in the vascular walls and intervening stroma of resected brain arteriovenous malformation (bAVM) specimens, even in unruptured and previously untreated lesions. Macrophages may play a critical role in bAVM progression to rupture, and could serve as a marker for rupture risk. We assessed feasibility of imaging macrophages within the bAVM nidus using ferumoxytol-enhanced MRI in four patients with already diagnosed bAVMs using iron-sensitive imaging (ISI; T2*-GE-MRI sequence). Patients were imaged at baseline and at either 1 day (n=2) or 5 days (n=2) after infusion of 5mg/kg of ferumoxytol. Residual intravascular ferumoxytol obscured evaluation for uptake in bAVM vascular walls and stroma at the 1-day time point. The two cases imaged at 5 days showed less intravascular tracer but had signal loss in the nidal region consistent with ferumoxytol localization. One case underwent surgical resection; there was prominent vascular wall CD68 staining. Ferumoxytol-enhanced-MRI for assessing bAVM inflammatory cell burden appears feasible and has the potential to be developed as a biomarker to study lesional inflammatory events.
Arteriovenous malformations; Inflammation; Magnetic resonance imaging; Ferumoxytol; USPIO
The limited symptom relief and side effects of current Alzheimer’s disease (AD) medications warrant urgent discovery and study of new anti-AD agents. The “cholinergic hypothesis” of AD prompts us to search for plant-derived acetylcholineesterase (AChE) inhibitors such as galanthamine that has been licensed in Europe for AD treatment. We used the unique amyloid β-expressing transgenic C. elegans CL4176, which exhibits paralysis when human Aβ1–42 is induced, to study two natural benzylphenethylamine alkaloids isolated from Lycoris radiata (L’ Her.) Herb, galanthamine and haemanthidine, and their synthetic derivatives 1,2-Di-O-acetyllycorine and 1-O-acetyllycorine for their anti-paralysis effects. Our data indicate that these Lycoris compounds effectively delay the paralysis of CL4176 worms upon temperature up-shift, and prolong the lives of these transgenic worms. Lycoris compounds were shown to significantly inhibit the gene expression of ace-1 and ace-2. Additionally, the Lycoris compounds may modulate inflammatory and stress-related gene expressions to combat the Aβ-toxicity in C. elegans.
Background and Purpose
We investigated whether brain arteriovenous malformation (bAVM) silent intralesional microhemorrhage (SIM), i.e., asymptomatic bleeding in the nidal compartment, might serve as a marker for increased risk of symptomatic intracranial hemorrhage (ICH). We evaluated two markers to assess the occurrence of SIM: neuroradiological assessment of evidence of old hemorrhage (EOOH)— imaging evidence of bleeding before the outcome events, and hemosiderin positivity in H&E-stained paraffin block sections.
We included cases from a bAVM database with recorded neuroradiological data or available surgical paraffin blocks. Using two endpoints, index ICH and new ICH after diagnosis (censored at treatment, loss to follow-up, or death), we performed logistic or Cox regression to assess EOOH and hemosiderin positivity, adjusting for age, sex, deep-only venous drainage, maximal bAVM size, deep location, and associated arterial aneurysms.
EOOH was present in 6.5% (n=975) of patients and highly predictive of index ICH (p<0.001; OR=3.97; 95% CI, 2.1-7.5), adjusting for other risk factors. In a multivariable model (n=643), EOOH was an independent predictor of new ICH (HR=3.53; 95% CI=1.35-9.23; p=.010). Hemosiderin positivity was found in 36.2% (29.6% in unruptured; 47.8% in ruptured; p=.04), and associated with index ICH in univariate (OR=2.18; 95%CI 1.03-4.61; p=.042; n=127) and multivariable models (OR=3.64; 95% CI=1.11-12.00; p=.034; n=79).
The prevalence of SIM is high and there is evidence for an association with both index and subsequent ICH. Further development of means to detect SIM during bAVM evaluation may present an opportunity to improve risk-stratification, especially for unruptured bAVMs.
brain arteriovenous malformation; hemorrhage; risk factor; survival; brain microbleed; hemosiderin
Lesions in the insula and basal ganglia can be risky to resect due to their depth and proximity to critical structures, particularly in the dominant hemisphere. Transsylvian approaches shorten the surgical distance to these lesions, preserve perisylvian temporal and frontal cortex, and minimize brain transgression.
We report our experience with transsylvian-transinsular approaches to vascular lesions.
The anterior approach opened the sphenoidal and insular portions of the Sylvian fissure and exposed the limen insulae and short gyri, whereas the posterior approach opened the insular and opercular portions of the Sylvian fissure and exposed the circular sulcus and long gyri.
41 patients with vascular lesions (24 arteriovenous malformations (AVM) and 17 cavernous amlformations (CM)) were treated surgically with a transsylvian-transinsular approach. Complete resection was obtained in 87.5% of AVMs and 95% of CMs. Permanent neurologic morbidity related to surgery was observed in 2 AVM patients (5%), with the remaining 39 patients (95%) improved or unchanged postoperatively (modified Rankin Scale scores 0–2 in 83%). There were no new language deficits in patients with dominant hemisphere lesions.
Transsylvian-transinsular approaches safely expose vascular pathology in or deep to the insula while preserving overlying eloquent cortex in the frontal and temporal lobes. The anterior transsylvian-transinsular approach can be differentiated from the posterior approach based on technical differences in splitting the Sylvian fissure and anatomical differences in final exposure. Discriminating patient selection and careful microsurgical technique are essential.
Macrophages play a critical role in cerebral aneurysm formation and rupture. The purpose of this study is to demonstrate the feasibility and optimal parameters of imaging macrophages within human cerebral aneurysm wall using ferumoxytol-enhanced-MRI.
Methods and Results
19 unruptured aneurysms in 11 patients were imaged using T2*-GE-MRI sequence. Two protocols were utilized. Protocol A: infusion of 2.5mg/kg of ferumoxytol and imaging at day 0 and 1. Protocol B: infusion of 5mg/kg of ferumoxytol and imaging at day 0 and 3. All images were reviewed independently by two neuroradiologists to assess for ferumoxytol-associated loss of MRI signal intensity within aneurysm wall. Aneurysm tissue was harvested for histologic analysis.
Fifty percent(5/10) of aneurysms in protocol A showed ferumoxytol-associated signal changes in aneurysm walls compared to 78% (7/9) of aneurysms in protocol B. Aneurysm tissue harvested from patients infused with ferumoxytol stained positive for both CD68+, demonstrating macrophage infiltration, and Prussian-Blue, demonstrating uptake of iron particles. Tissue harvested from controls stained positive for CD68 but not Prussian-Blue.
Imaging with T2*-GE-MRI at 72 hours post-infusion of 5mg/kg of ferumoxytol establishes a valid and useful approximation of optimal dose and timing parameters for macrophages imaging within aneurysm wall. Further studies are needed to correlate these imaging findings with risk of intracranial aneurysm rupture.
Intracranial Aneurysm; Inflammation; Magnetic Resonance Imaging; Ferumoxytol; USPIO
Many significant microsurgical series of patients with giant aneurysms predate changes in practice during the endovascular era.
A contemporary surgical experience is presented to examine changes in management relative to earlier reports, to establish the role of open microsurgery in the management strategy, and to quantify results for comparison with evolving endovascular therapies.
During a 13-year period, 140 patients with 141 giant aneurysms were treated surgically. 100 aneurysms (71%) were located in the anterior circulation, and 41 aneurysms were located in the posterior circulation.
108 aneurysms (77%) were completely occluded, 14 aneurysms (10%) had minimal residual aneurysm, and 16 aneurysms (11%) were incompletely occluded with reversed or diminished flow. 3 patients with calcified aneurysms were coiled after unsuccessful clipping attempts. 18 patients died in the perioperative period (surgical mortality, 13%). Bypass-related complications resulted from bypass occlusion (7 patients), aneurysm hemorrhage due to incomplete aneurysm occlusion (4 patients), or aneurysm thrombosis with perforator or branch artery occlusion (4 patients). 13 patients were worse at late follow-up (permanent neurological morbidity, 9%; mean length of follow-up, 23±1.9 months). Overall, good outcomes (GOS 5 or 4) were observed in 114 patients (81%) and 109 patients (78%) were improved or unchanged after therapy.
A heavy reliance on bypass techniques plus indirect giant aneurysm occlusion distinguishes this contemporary surgical experience from earlier ones, and obviates the need for hypothermic circulatory arrest. Experienced neurosurgeons can achieve excellent results with surgery as the “first-line” management approach and endovascular techniques as adjuncts to surgery.
bypass; direct clipping; giant aneurysm; indirect aneurysm occlusion; microsurgery
Brain arteriovenous malformations (BAVMs) are an important cause of intracranial hemorrhage (ICH) in young adults. Gene expression profiling of blood has led to the identification of stroke biomarkers, and may help identify BAVM biomarkers and illuminate BAVM pathogenesis. It is unknown whether blood gene expression profiles differ between 1) BAVM patients and healthy controls, or 2) unruptured and ruptured BAVM patients at presentation. We characterized blood transcriptional profiles in 60 subjects (20 unruptured BAVM, 20 ruptured BAVM, and 20 healthy controls) using Affymetrix whole genome expression arrays. Expression differences between groups were tested by ANOVA, adjusting for potential confounders. Genes with absolute fold change ≥ 1.2 (false discovery rate corrected p ≤ 0.1) were selected as differentially expressed and evaluated for over-representation in KEGG biological pathways (p ≤ 0.05). Twenty-nine genes were differentially expressed between unruptured BAVM patients and controls, including 13 which may be predictive of BAVM. Patients with ruptured BAVM compared to unruptured BAVM differed in expression of 1490 genes, with over-representation of genes in 8 pathways including MAPK, VEGF, Wnt signaling and several inflammatory pathways. These results suggest clues to the pathogenesis of BAVM and/or BAVM rupture and point to potential biomarkers or new treatment targets.
arteriovenous malformation; blood; gene expression; intracranial hemorrhage; microarray analysis
Elevated levels of B-type natriuretic peptide (BNP) have been associated with cardiac dysfunction and adverse neurological outcomes after subarachnoid hemorrhage (SAH). We sought to determine whether elevated levels of BNP are independently associated with radiographic cerebral infarction after SAH.
Plasma BNP levels were measured after admission, a mean of 5.5 ± 3.0 days after SAH onset. Cerebral infarction was determined by retrospective review of computerized tomography (CT) scans. Cerebral vasospasm was confirmed by the presence of vascular narrowing on cerebral angiogram. The association between BNP and cerebral infarction was quantified using multivariable logistic regression and reverse stepwise elimination of clinical covariates. A stratified analysis was performed to quantify the association between BNP levels and infarction in patients with and without angiographic vasospasm.
BNP levels were measured from 119 subjects. The median BNP level was 105 pg/ml (interquartile range 37–275 pg/ml). In our multivariable model, the top quartile of BNP levels (≥276 pg/ml) were associated with an increased odds of cerebral infarction (OR 4.2, P = 0.009). The stratified analysis showed that the association between BNP and infarction was strongest in patients without angiographic vasospasm (OR 7.8, P = 0.006).
Elevated levels of BNP are strongly and independently associated with cerebral infarction, and the association is most pronounced in patients without angiographic vasospasm. These results provide further evidence that other mechanisms can contribute to infarction, and BNP may be a useful biomarker in detecting patients at risk for adverse outcomes without large vessel vasospasm.
Subarachnoid hemorrhage; Cerebral infarction; Cerebral vasospasm; B-type natriuretic peptide
Estimation of the stability of dysmorphic fusiform aneurysms of the intra-cranial internal carotid artery requires precise monitoring of their volumes. In this report we apply a method using MRI and 3D post-processing to study the evolution of these aneurysms on a prospective cohort of patients not immediately suitable for surgery or endovascular treatment.
Materials and Methods
Ten patients with fusiform aneurysms of the intra-cranial internal carotid artery underwent serial MRI studies. Five patients were studied at two time points and the remainder at multiple time points (mean delay between studies: 12.6 +/− 3.8 months). For each patient, studies from all time points were co-registered. Volumes of each vessel component were calculated.
Mean aneurysm volume was 833 +/− 878 mm3. Mean annual rate of volume progression was 1.37 +/− 2.09 % per year. All the aneurysms were thrombus-free.
This study indicates that, given the relatively low rate of progression of these dysplastic fusiform aneurysms and the complexity of their shape, 3D quantitative volumetric methods can be helpful in monitoring whether any growth has occurred.
Brain arteriovenous malformations (bAVM) are an important cause of hemorrhagic stroke. The underlying mechanisms are not clear. No animal model for adult bAVM is available for mechanistic exploration. Patients with Hereditary Hemorrhagic Telangiectasia Type2 (HHT2) with activin receptor-like kinase 1 (ALK1; ACVRL1) mutations have a higher incidence of bAVM than the general population. We tested the hypothesis that VEGF stimulation with regional homozygous deletion of Alk1 induces severe dysplasia in the adult mouse brain, akin to human bAVM.
Alk12f/2f (exons 4–6 flanked by loxP sites) and wild-type (WT) mice (8–10 weeks old) were injected with Ad-Cre (2×107 PFU, adenoviral vector expressing Cre recombinase) and AAV-VEGF (2×109 genome copies, adeno-associated viral vectors expressing VEGF) into the basal ganglia. At 8 weeks, blood vessels were analyzed.
Gross vascular irregularities were seen in Alk1 2f/2f mouse brain injected with Ad-Cre and AAV-VEGF. The vessels were markedly enlarged with abnormal patterning resembling aspects of the human bAVM phenotype, displayed altered expression of the arterial and venous markers (EphB4 and Jagged-1), and showed evidence of arteriovenous shunting. Vascular irregularities were not seen in similarly treated WT mice.
Our data indicate that post-natal, adult formation of the human disease bAVM is possible, and that both genetic mutation and angiogenic stimulation are necessary for lesion development. Our work not only provides a testable adult mouse bAVM model for the first time, but also suggests that specific medical therapy can be developed to slow bAVM growth and potentially stabilize the rupture-prone abnormal vasculature.
Brain arteriovenous malformations (BAVM) are high-flow vascular lesions prone to intracranial hemorrhage (ICH). Abnormal angiogenesis is a key characteristic of BAVM tissue. Angiopoietin-like 4 (ANGPTL4), a secreted glycoprotein, is thought to be involved in angiogenesis and required for proper postnatal blood vessel partitioning. We investigated whether common single nucleotide polymorphisms (SNPs) in ANGPTL4 were associated with risk of BAVM or ICH.
Methods and Results
We conducted a case-control study of 216 Caucasian BAVM cases and 246 healthy controls, and a secondary case-only analysis, comparing 83 ruptured (ICH) with 133 unruptured BAVM cases at presentation. Four tagSNPs in ANGPTL4 captured variation over a 10-kb region (rs2278236, rs1044250, rs11672433, and rs1808536) and were tested for association with BAVM or ICH. The minor allele (A) of rs11672433 (exon 6, Pro389Pro) was associated with an increased risk of BAVM (p = 0.006), which persisted after adjusting for multiple comparisons (p = 0.03). After adjustments for age and sex, carriers of the minor allele (A) remained at higher risk for BAVM compared to noncarriers (odds ratio, OR = 1.56; 95% confidence interval, CI = 1.01–2.41; p = 0.046) and risk of BAVM was increased with increasing copy of the minor A allele (OR = 1.49, 95% CI = 1.03–2.15; ptrend = 0.03). Five common haplotypes (frequency >1%) were inferred; overall haplotype distribution differed between BAVM cases and controls (χ2 = 12.2, d.f. = 4, p = 0.02). Neither SNPs (p > 0.05) nor haplotype distribution (χ2 = 1.1, d.f. = 4, p = 0.89) were associated with risk of ICH among BAVM cases.
A synonymous SNP in ANGPTL4 and haplotypes carrying it are associated with risk of BAVM but not with ICH presentation in BAVM cases.
Arteriovenous malformations; Cerebrovascular disorders; Epidemiology; Genetics; Intracranial hemorrhage
Background and Purpose
Abnormal vascular remodeling triggered by hemodynamic stresses and inflammation is believed to be a key process in the pathophysiology of intracranial aneurysms. Numerous studies have shown infiltration of inflammatory cells, especially macrophages, into intracranial aneurysmal walls in humans. Using a mouse model of intracranial aneurysms, we tested whether macrophages play critical roles in the formation of intracranial aneurysms.
Intracranial aneurysms were induced in adult male mice using a combination of a single injection of elastase into the cerebrospinal fluid and angiotensin-II-induced hypertension. Aneurysm formation was assessed three weeks later. Roles of macrophages were assessed utilizing clodronate liposome-induced macrophage depletion. In addition, the incidence of aneurysms was assessed in mice lacking monocyte chemotactic protein-1 (MCP-1, CCL2), and mice lacking matrix metalloproteinase-12 (MMP-12, macrophage elastase).
Intracranial aneurysms in this model showed leukocyte infiltration into the aneurysmal wall, the majority of leukocytes being macrophages. Mice with macrophage depletion had a significantly reduced incidence of aneurysms compared to control mice (1/10 vs. 6/10; P < 0.05). Similarly, there was a reduced incidence of aneurysms in mice lacking MCP-1, compared to incidence of aneurysms in wild-type mice (2/10 vs. 14/20, P < 0.05). There was no difference in the incidence of aneurysms between mice lacking MMP-12 and wild-type mice.
These data suggest critical roles of macrophages and proper macrophage functions in the formation of intracranial aneurysms in this model.
Intracranial aneurysm; stroke; inflammation; animal model; macrophage
Brain and spinal cord arteriovenous malformations (AVMs) are characterized by aberrant angiogenesis and vascular remodeling. Endothelial progenitor cells (EPCs) can be recruited by stromal cell-derived factor-1 (SDF-1), and participate in vascular remodeling in both physiological and pathological settings. We hypothesized that there was increased EPC levels in the brain and spinal cord AVM nidus.
Microsurgical specimens without endovascular embolization and radiosurgery from the brain (n=12) and spinal cord (n=5) AVMs were examined. Hemangioblastoma, meningioma, cerebral cortex obtained from epilepsy surgery, and the basilar artery (BA) from the autopsy were chosen for control comparisons. EPCs were identified as cells that were double-positive for the stem cell marker CD133 and the endothelial cell marker VEGFR-2 (vascular endothelial growth factor receptor-2 or KDR). In addition, SDF-1 was characterized by immunohistochemistry.
Both brain and spinal AVM tissues displayed more CD133, SDF-1, and CD68-positive signals than epilepsy and basilar artery control tissues. The level of EPCs was increased in the brain and spinal cord AVM nidus, mainly at the edge of the vessel wall. The expression of SDF-1 was co-localized with CD31-positive and α-smooth muscle cells, and was predominantly found within the vessel wall.
Our data demonstrate that EPCs are present in the nidus of the brain and spinal cord AVMs, which may mediate pathological vascular remodeling and impact the clinical course of AVMs.
Angiogenesis; Endothelial progenitor cell; Stromal cell-derived factor-1; Vascular malformation
Estimating risk of intracranial hemorrhage (ICH) for patients with unruptured brain arteriovenous malformations (AVMs) in the natural course is essential for assessing risks and benefits of treatment. Traditionally, the survival period starts at the time of diagnosis and ends at ICH, but most patients are quickly censored because of treatment. Alternatively, a survival period from birth to first ICH, censoring at the date of diagnosis, has been proposed. The authors quantitatively compared these 2 timelines using survival analysis in 1,581 Northern California brain AVM patients (2000–2007). Time-shift analysis of the birth-to-diagnosis timeline and maximum pseudolikelihood identified the point at which the 2 survival curves overlapped; the 95% confidence interval was determined using bootstrapping. Annual ICH rates per 100 patient-years were similar for both the birth-to-diagnosis (1.27, 95% confidence interval (CI): 1.18, 1.36) and the diagnosis-to-ICH (1.17, 95% CI: 0.89, 1.53) timelines, despite differences in curve morphology. Shifting the birth-to-diagnosis timeline an optimal amount (10.3 years, 95% CI: 3.3, 17.4) resulted in similar ICH survival curves (P = 0.979). These results suggest that the unconventional birth-to-diagnosis approach can be used to analyze risk factors for natural history risk in unruptured brain AVM patients, providing greater statistical power. The data also suggest a biologic change around age 10 years influencing ICH rate.
arteriovenous malformations; intracranial hemorrhages; risk factors; survival analysis
Patient age, hemorrhagic presentation, nidal diffuseness, and deep perforating artery supply are important factors when selecting patients with brain arteriovenous malformations for surgery. We hypothesized that these factors outside of the Spetzler-Martin grading system could be combined into a simple, supplementary grading system that would accurately predict neurological outcome and refine patient selection.
A consecutive, single-surgeon series of 300 patients with AVMs treated microsurgically was analyzed in terms of change between preoperative and final postoperative Modified Rankin Scale scores. Three different multivariable logistic models (full, Spetzler-Martin, and supplementary models) were constructed to test the association of combined predictor variables with the change in MRS score. A simplified supplementary grading system was developed from the data which combined age, hemorrhagic presentation, and diffuseness in a manner analogous to the Spetzler-Martin grading system, with points assigned according to each variable and added together for a supplementary AVM grade.
Predictive accuracy was highest for the full multivariable model (receiver operating characteristic curve area, 0.78), followed by the supplementary model (0.73), and least for the Spetzler-Martin model (0.66). Predictive accuracy of the simplified supplementary grade was significantly better than that of the Spetzler-Martin grade (P=0.042), with ROC curve areas of 0.73 and 0.65, respectively. The predictive accuracy of the supplementary grade was only slightly less than a full point score with all 7 weighted variables (P=0.364), with areas under the ROC curve of 0.73 and 0.75, respectively.
This new AVM grading system supplements rather than replaces the well established Spetzler-Martin grading system, and is a better predictor of neurological outcomes after AVM surgery. The supplementary grading scale has high predictive accuracy on its own and stratifies surgical risk more evenly. Supplementary grades can confirm risk predicted by the Spetzler-Martin grade, or in cases of mismatched grades, may alter management decisions. The supplementary grading system is easily applicable at the bedside, where it is intended to improve preoperative risk prediction and patient selection for surgery.
Arteriovenous malformation; Microsurgery; Patient selection; Prediction models; Spetzler-Martin grading system; Supplementary grading system
Evolution of intracranial aneurysms is known to be related to hemodynamic forces such as Wall Shear Stress (WSS) and Maximum Shear Stress (MSS). Estimation of these parameters can be performed using numerical simulations (computational fluid dynamics - CFD) but can also be directly measured with MRI using a time-dependent 3D phase-contrast sequence with encoding of each of the three components of the velocity vectors (7D-MRV). In order to study the accuracy of 7D-MRV in estimating these parameters in–vivo, in comparison with CFD, 7D-MRV and patient-specific CFD modeling was performed for three patients who had intracranial aneurysms. A visual and a quantitative analysis of the flow pattern and the distribution of velocities, MSS, and WSS were performed between the two techniques. Spearman's coefficients of correlation between the two techniques were 0.56 for the velocity field, 0.48 for MSS and 0.59 for WSS. Visual analysis and Bland-Altman plots showed a good agreement for flow pattern and velocities but large discrepancies for MSS and WSS. In conclusion, these results indicate that in-vivo 7D-MRV can be used to measure velocity flow fields and to estimate MSS and WSS but is not currently able to provide accurate quantification of these two last parameters.
Phase-contrast MRI; Computational Fluid Dynamics; Intracranial aneurysm; Wall Shear Stress