Persistent hemodynamic changes in ruptured brain arteriovenous malformations

Shortened Cerebral Circulation Time Predicts Resistance to Obliteration in High-Flow Brain Arteriovenous Malformations After Stereotactic Radiosurgery

BACKGROUND AND OBJECTIVES

Treatment selection for brain arteriovenous malformations (BAVMs) is complicated by BAVM size, location, and hemodynamics. Quantitative digital subtraction angiography is used to quantify the hemodynamic impact of BAVMs on cerebral circulation. This study investigated the association between cerebral circulation time and the complete obliteration (CO) rate of BAVMs after stereotactic radiosurgery (SRS).

METHODS

We analyzed the data of 143 patients who underwent SRS for BAVMs between January 2011 and December 2019 in our institute. Their pre-SRS magnetic resonance imaging and angiography images were analyzed to acquire BAVM characteristics and quantitative digital subtraction angiography parameters. Modified cerebral circulation time (mCCT) was defined as the time difference between the bolus arrival time of the ipsilateral cavernous internal carotid artery and that of the parietal vein, as determined from the lateral view of images obtained using digital subtraction angiography. Cox regression with hazard ratios and Kaplan-Meier analyses were conducted to determine the associations between the parameters and BAVM CO after SRS.

RESULTS

Of the 143 patients, 101 (70.6%) achieved BAVM CO. According to the multivariate analyses, an increased mCCT (hazard ratio: 1.24, P = .041) was the independent factor associated with BAVM CO after adjustment for age, sex, hemorrhagic presentation, a BAVM volume of >5 cm3, and a margin dose of >18 Gy. Individuals with an mCCT of ≤2.32 s had a lower 36-month probability of BAVM CO than did those with an mCCT of >2.32 s (44.1% ± 6.8% vs 63.3% ± 5.6%, P = .034).

CONCLUSION

The hemodynamic impact of high-flow BAVM demonstrated by a shortened mCCT is associated with a lower BAVM CO rate after SRS.

Rupture-Risk Stratifying Patients with Cerebral Arteriovenous Malformations Using Quantitative Hemodynamic Flow Measurements

Arteriovenous malformations (AVMs) are high-pressure, low-resistance arterial-venous shunts without intervening capillaries. Up to 60% of AVMs present with an intracranial hemorrhage; however, noninvasive neuroimaging has increasingly diagnosed incidental AVMs. AVM management depends on weighing the lifetime rupture risk against the risks of intervention. Although AVM rupture risk relies primarily on angioarchitectural features, measuring hemodynamic flow is gaining traction. Accurate understanding of AVM hemodynamic flow parameters will help endovascular neurosurgeons and interventional neuroradiologists stratify patients by rupture risk and select treatment plans. This review examines various neuroimaging modalities and their capabilities to quantify AVM flow, as well as the relationship between AVM flow and rupture risk. Quantitative hemodynamic studies on the relationship between AVM flow and rupture risk have not reached a clear consensus; however, the preponderance of data suggests that higher arterial inflow and lower venous outflow in the AVM nidus contribute to increased hemorrhagic risk. Future studies should consider using larger sample sizes and standardized definitions of hemodynamic parameters to reach a consensus. In the meantime, classic angioarchitectural features may be more strongly correlated with AVM rupture than the amount of blood flow.

Rupture-related quantitative hemodynamics of the supratentorial arteriovenous malformation nidus

OBJECTIVE

The hemodynamics of a brain arteriovenous malformation (AVM) nidus may be closely related to clinical presentation. The authors of this study aimed to explore the hemorrhagic quantitative hemodynamic indicators of the nidus through quantitative digital subtraction angiography (QDSA).

METHODS

The quantitative hemodynamic parameters were generated from QDSA. Three data sets were used to explore independent quantitative hemodynamic indicators associated with AVM rupture. The training data set was exploited to discover independent quantitative hemodynamic indicators of AVM rupture by performing univariate and multivariate logistic regression analyses. The authors plotted receiver operating characteristic curves to validate the diagnostic performance of the hemorrhagic hemodynamic indicators using the training and two external validation data sets. Kaplan-Meier survival analysis was adopted to verify the predictive power of these risk indicators of future hemorrhage in the external prospective validation data set.

RESULTS

A total of 151 patients were included in this study, 91 in the training set and 30 in each of the two validation sets. A higher stasis index and slower transnidal relative velocity (TRV) of the nidus were significantly correlated with AVM rupture. The areas under the curve (AUCs) of the stasis index (nidus) were 0.765 and 0.815 and those of the TRV (nidus) were 0.735 and 0.796, respectively, in the training and retrospective external validation sets. Kaplan-Meier survival analysis confirmed the validity of the stasis index and TRV in predicting future rupture risk in the prospective validation data set (p = 0.008 and 0.041, respectively, log-rank test).

CONCLUSIONS

A higher stasis index (nidus) and slower TRV (nidus) in QDSA were associated with AVM rupture and were effective indicators of future hemorrhage, suggesting that the core mechanisms underlying AVM rupture could be intravascular blood stasis and occlusive hyperemia of the nidus.

Quantified flow and angioarchitecture show similar associations with hemorrhagic presentation of brain arteriovenous malformations

INTRODUCTION

The purpose of our study was to elucidate the impact of brain arteriovenous malformation (BAVM) flow and wall shear stress (WSS) on angioarchitecture and to evaluate their association with hemorrhagic presentations.

MATERIALS AND METHODS

Forty-one patients with BAVMs were evaluated by phase-contrast MR angiography. Volume flow rate and WSS were quantified. Angioarchitectural features such as location, angiogenesis, venous stenosis, venous ectasia, venous phlebitis, venous rerouting, exclusive deep vein and venous sac were evaluated by two neuroradiologists. The correlation between BAVM flow and size was evaluated with Spearman correlation coefficients. Differences of size, flow, and WSS between the hemorrhagic and non-hemorrhagic groups, the seizure and non-seizure groups, and between the different groups based on angioarchitecture were evaluated with Mann-Whitney U tests. Accuracy in predicting hemorrhage was evaluated with receiver operating characteristic curves.

RESULT

BAVM flow was highly correlated with volume (ρ = 0.77). Higher flow was more commonly associated with angiogenesis, venous ectasia, venous rerouting, and venous phlebitis. Flow and angioarchitecture showed similar efficacy in differentiating hemorrhagic from non-hemorrhagic BAVMs. WSS did not demonstrate differences across any clinical groups.

CONCLUSION

Flow quantification and angioarchitecture analysis of BAVMs showed similar efficacy as evaluated by associations with hemorrhagic presentation. High flow affects both arterial and venous angioarchitecture, reflecting the nature of low vascular resistance in BAVMs.

Compactness index: a radiosurgery outcome predictor for patients with unruptured brain arteriovenous malformations

OBJECTIVE

The goal of the study was to define and quantify brain arteriovenous malformation (bAVM) compactness and to assess its effect on outcomes after Gamma Knife radiosurgery (GKRS) for unruptured bAVMs.

METHODS

Unsupervised machine learning with fuzzy c-means clustering was used to differentiate the tissue constituents of bAVMs on T2-weighted MR images. The percentages of vessel, brain, and CSF were quantified. The proposed compactness index, defined as the ratio of vasculature tissue to brain tissue, categorized bAVM morphology into compact, intermediate, and diffuse types according to the tertiles of this index. The outcomes of interest were complete obliteration and radiation-induced changes (RICs).

RESULTS

A total of 209 unruptured bAVMs treated with GKRS were retrospectively included. The median imaging and clinical follow-up periods were 49.2 and 72.3 months, respectively. One hundred seventy-three bAVMs (82.8%) achieved complete obliteration after a median latency period of 43.3 months. The rates of RIC and permanent RIC were 76.1% and 3.8%, respectively. Post-GKRS hemorrhage occurred in 14 patients (6.7%), resulting in an annual bleeding risk of 1.0%. Compact bAVM, smaller bAVM volume, and exclusively superficial venous drainage were independent predictors of complete obliteration. Diffuse bAVM morphology, larger bAVM volume, and higher margin dose were independently associated with RICs.

CONCLUSIONS

The compactness index quantitatively describes the compactness of unruptured bAVMs. Moreover, compact bAVMs may have a higher obliteration rate and a smaller risk of RICs than diffuse bAVMs. This finding could help guide decision-making regarding GKRS treatment for patients with unruptured bAVMs.

Hemodynamic Analysis of Cerebral AVMs with 3D Phase-Contrast MR Imaging

BACKGROUND AND PURPOSE

The hemodynamics associated with cerebral AVMs have a significant impact on their clinical presentation. This study aimed to evaluate the hemodynamic features of AVMs using 3D phase-contrast MR imaging with dual velocity-encodings.

MATERIALS AND METHODS

Thirty-two patients with supratentorial AVMs who had not received any previous treatment and had undergone 3D phase-contrast MR imaging were included in this study. The nidus diameter and volume were measured for classification of AVMs (small, medium, or large). Flow parameters measured included apparent AVM inflow, AVM inflow index, apparent AVM outflow, AVM outflow index, and the apparent AVM inflow-to-outflow ratio. Correlation coefficients between the nidus volume and each flow were calculated. The flow parameters between small and other AVMs as well as between nonhemorrhagic and hemorrhagic AVMs were compared.

RESULTS

Patients were divided into hemorrhagic (n = 8) and nonhemorrhagic (n = 24) groups. The correlation coefficient between the nidus volume and the apparent AVM inflow and outflow was .83. The apparent AVM inflow and outflow in small AVMs were significantly smaller than in medium AVMs (P < .001 for both groups). The apparent AVM inflow-to-outflow ratio was significantly larger in the hemorrhagic AVMs than in the nonhemorrhagic AVMs (P = .02).

CONCLUSIONS

The apparent AVM inflow-to-outflow ratio was the only significant parameter that differed between nonhemorrhagic and hemorrhagic AVMs, suggesting that a poor drainage system may increase AVM pressure, potentially causing cerebral hemorrhage.

Signal intensity ratio of draining vein on silent MR angiography as an indicator of high-flow arteriovenous shunt in brain arteriovenous malformation

OBJECTIVES

To evaluate whether the signal intensity ratio (rSI) of the draining vein on silent MR angiography is correlated with arteriovenous (A-V) transit time on digital subtraction angiography (DSA), thereby identifying high-flow A-V shunt in brain arteriovenous malformation (BAVM), and to analyze whether the rSI and the characteristic of draining veins on silent MRA are associated with hemorrhage presentation.

METHODS

Eighty-one draining veins of 46 participants with BAVM (mean age 33.2 ± 16.9 years) who underwent silent MRA and DSA were evaluated retrospectively. The correlation between the rSI of the draining vein on silent MRA and A-V transit time on DSA was examined. The AUC-ROC was obtained to evaluate the performance of the rSI in determining the presence of high-flow A-V shunt. The characteristics of draining veins with the maximum rSI (rSImax) were further compared between the hemorrhagic and non-hemorrhagic untreated BAVM.

RESULTS

The rSI of each draining vein on silent MRA was significantly correlated with A-V transit time from DSA (r = -0.81, p < .001). The AUC-ROC was 0.89 for using the rSI to determine the presence of high-flow A-V shunt. A cut-off rSI value of 1.09 yielded a sensitivity of 82.4% and a specificity of 82.8%. The draining vein with rSImax and no ectasia was significantly more observed in the hemorrhagic group (p = 0.045).

CONCLUSIONS

The rSI of the draining vein on silent MRA is significantly correlated with A-V transit time on DSA, and it can be used as an indicator of high-flow A-V shunt in BAVM.

KEY POINTS

• The signal intensity ratio (rSI) of the draining vein on silent MRA significantly correlated with arteriovenous (A-V) transit time of brain arteriovenous malformation (BAVM) on digital subtraction angiography (DSA). • The area under the receiver operating characteristic curve (AUC) was 0.89 for using the rSI of draining veins to determine high-flow A-V shunt. • Draining veins with maximum rSI and no ectasia were significantly more observed in the hemorrhagic group of BAVM (p = 0.045).

Stagnant venous outflow in ruptured arteriovenous malformations revealed by delayed quantitative digital subtraction angiography

PURPOSE

To investigate the reproducibility of quantitative digital subtraction angiography (QDSA) measurements and their associations with brain arteriovenous malformation (BAVM) hemorrhage.

METHODS

From 2011-2019, 37 patients with BAVMs who had undergone both diagnostic and stereotactic DSA were divided into hemorrhagic and nonhemorrhagic groups. QDSA analysis was performed on the 2 DSA exams. The inter-exam reliabilities of QDSA measurements across the diagnostic and stereotactic DSA were tested using intraclass correlation coefficients (ICCs). Demographics, BAVM characteristics, and QDSA results for the hemorrhagic and nonhemorrhagic groups were compared.

RESULTS

Fifteen of 37 (40.5 %) patients presented with hemorrhage were associated with smaller BAVM volume and the presence of intranidal aneurysm and exclusive deep venous drainage. The median interval between the diagnostic and stereotactic DSA was 49 days and did not differ between the groups. In both groups, the inter-exam QDSA measurements were more reliable for drainage veins and transnidal time (ICCs ranged from 0.38-0.93) than for feeding arteries (ICCs ranged from 0.01-0.74). Among the venous parameters, the hemorrhagic group had lower peak density, area under the curve, inflow gradient, and outflow gradient on both DSA exams and larger full width at half maximum and stasis index on the stereotactic DSA exam than the nonhemorrhagic group.

CONCLUSIONS

In BAVMs, the QDSA measurements for veins are more reliable than those for arteries. QDSA analysis reflecting stagnant venous drainage is associated with BAVM hemorrhage, but may be confounded by the acute hemodynamic change after hemorrhage.

Interrater Reliability in the Measurement of Flow Characteristics on Color-Coded Quantitative DSA of Brain AVMs

BACKGROUND AND PURPOSE

Hemodynamic features of brain AVMs may portend increased hemorrhage risk. Previous studies have suggested that MTT is shorter in ruptured AVMs as assessed on quantitative color-coded parametric DSA. This study assesses the interrater reliability of MTT measurements obtained using quantitative color-coded DSA.

MATERIALS AND METHODS

Thirty-five color-coded parametric DSA images of 34 brain AVMs were analyzed by 4 neuroradiologists with experience in interventional neuroradiology. Hemodynamic features assessed included MTT of the AVM and TTP of the dominant feeding artery and draining vein. Agreement among the 4 raters was assessed using the intraclass correlation coefficient.

RESULTS

The interrater reliability among the 4 raters was poor (intraclass correlation coefficient = 0.218; 95% CI, 0.062-0.414; P value = .002) as it related to MTT assessment. When the analysis was limited to cases in which the raters selected the same image to analyze and selected the same primary feeding artery and the same primary draining vein, interrater reliability improved to fair (intraclass correlation coefficient  = 0.564; 95% CI, 0.367-0.717; P < .001).

CONCLUSIONS

Interrater reliability in deriving color-coded parametric DSA measurements such as MTT is poor so minor differences among raters may result in a large variance in MTT and TTP results, partly due to the sensitivity and 2D nature of the technique. Reliability can be improved by defining a standard projection, feeding artery, and draining vein for analysis.

Stasis index from hemodynamic analysis using quantitative DSA correlates with hemorrhage of supratentorial arteriovenous malformation: a cross-sectional study

OBJECTIVE

Assessments of hemorrhage risk based on angioarchitecture have yielded inconsistent results, and quantitative hemodynamic studies have been limited to small numbers of patients. The authors examined whether cerebral hemodynamic analysis using quantitative digital subtraction angiography (QDSA) can outperform conventional DSA angioarchitecture analysis in evaluating the risk of hemorrhage associated with supratentorial arteriovenous malformations (AVMs).

METHODS

A cross-sectional study was performed by retrospectively reviewing adult supratentorial AVM patients who had undergone both DSA and MRI studies between 2011 and 2017. Angioarchitecture characteristics, DSA parameters, age, sex, and nidus volume were analyzed using univariate and multivariate logistic regression, and QDSA software analysis was performed on DSA images. Based on the QDSA analysis, a stasis index, defined as the inflow gradient divided by the absolute value of the outflow gradient, was determined. The receiver operating characteristic (ROC) curve was used to compare diagnostic performances of conventional DSA angioarchitecture analysis and analysis using hemodynamic parameters based on QDSA.

RESULTS

A total of 119 supratentorial AVM patients were included. After adjustment for age at diagnosis, sex, and nidus volume, the exclusive deep venous drainage (p < 0.01), observed through conventional angioarchitecture examination using DSA, and the stasis index of the most dominant drainage vein (p = 0.02), measured with QDSA hemodynamic analysis, were independent risk factors for hemorrhage. The areas under the ROC curves for the conventional DSA method (0.75) and QDSA hemodynamics analysis (0.73) were similar. A venous stasis index greater than 2.18 discriminated the hemorrhage group with a sensitivity of 52.6% and a specificity of 81.5%.

CONCLUSIONS

In QDSA, a higher stasis index of the most dominant drainage vein is an objective warning sign associated with supratentorial AVM rupture. Risk assessments of AVMs using QDSA and conventional DSA angioarchitecture were equivalent. Because QDSA is a complementary noninvasive approach without extra radiation or contrast media, comprehensive hemorrhagic risk assessment of cerebral AVMs should include both DSA angioarchitecture and QDSA analyses.

Stagnant Venous Outflow Predicts Brain Arteriovenous Malformation Obliteration After Gamma Knife Radiosurgery Without Prior Intervention

BACKGROUND

Gamma Knife radiosurgery (GKRS) obliterates 65% to 82% of brain arteriovenous malformations (BAVMs).

OBJECTIVE

To explore the impact of hemodynamics on GKRS outcomes.

METHODS

We retrospectively (2011-2017) included 98 patients with BAVMs who had received GKRS alone. Two evaluators, blinded to the outcomes, analyzed the pre-GKRS angiography and magnetic resonance images to obtain the morphological characteristics and quantitative digital subtraction angiography (QDSA) parameters. The venous stasis index was defined as the inflow gradient divided by the absolute value of the outflow gradient. Patients’ follow-up magnetic resonance or digital subtraction angiography images were evaluated for the presence of complete obliteration (CO). Cox regression and Kaplan–Meier analyses were conducted to determine the correlations between the parameters and outcomes.

RESULTS

Among the 98 patients, 63 (63.4%) achieved CO after GKRS at a median latency period of 31 mo. In multivariable analyses with adjustments for age and sex, increased BAVM volume (hazard ratio (HR) 0.949, P = .022) was an independent characteristic predictor, and venous stenosis (HR 2.595, P = .009), venous rerouting (HR 0.375, P = .022), and larger stasis index (HR 1.227, P = .025) were independent angiographic predictors of CO. BAVMs with a stasis index of &gt;1.71 had a higher 36-mo probability of CO than those with a stasis index of ≤1.71 (61.1% vs 26.7%, P &lt; .001).

CONCLUSION

BAVMs with a larger stasis index, indicating more stagnant venous outflow, may predict obliteration after GKRS. QDSA analysis may help in predicting BAVM treatment outcomes and making therapeutic decisions.

Contrast Time-Density Time on Digital Subtraction Angiography Correlates With Cerebral Arteriovenous Malformation Flow Measured by Quantitative Magnetic Resonance Angiography, Angioarchitecture, and Hemorrhage

BACKGROUND

Digital subtraction angiography (DSA) currently provides angioarchitectural features of cerebral arteriovenous malformations (AVMs) but its role in the hemodynamic evaluation of AVMs is poorly understood.

OBJECTIVE

To assess contrast time-density time (TT) on DSA relative to AVM flow measured using quantitative magnetic resonance angiography (QMRA).

METHODS

Patients seen at our institution between 2007 and 2014 with a supratentorial AVM and DSA and QMRA obtained prior to any treatment were retrospectively reviewed. Regions of interest were selected on the draining veins at the point closest to the nidus. TT on DSA was defined as time needed for contrast to change image intensity from 10% to 100%, 100% to 10%, and 25% to 25%. TT was correlated to AVM total flow, angioarchitectural features, and hemorrhage.

RESULTS

Twenty-eight patients (mean age 35.6 yr) were included. Six patients presented with hemorrhage. Mean AVM volume was 11.42 mL (range 0.3-57.7 mL). Higher total AVM flow significantly correlated with shorter TT100%-10% and TT25%-25% (P = .02, .02, respectively). Presence of venous stenosis correlated significantly with shorter TT100%-10% (P = .04) and TT25%-25% (P = .04). AVMs with a single draining vein exhibited longer TT25%-25% compared to those with multiple draining veins (P = .04). Ruptured AVMs had significantly shorter TT10%-100% compared to unruptured AVMs (P = .05).

CONCLUSION

TT on DSA correlates with cerebral AVM flow measured using QMRA and with AVM angioarchitecture and hemorrhagic presentation. Thus, TT may be used to indirectly estimate AVM flow during angiography in real-time and may also be an indicator of important AVM characteristics associated with outflow resistance and increased rupture risk, such as venous stenosis.

Risk factors for hemorrhage of brain arteriovenous malformation

Patients with brain arteriovenous malformation (bAVM) are at risk of intracranial hemorrhage (ICH). Overall, bAVM accounts for 25% of hemorrhagic strokes in adults <50 years of age. The treatment of unruptured bAVMs has become controversial, because the natural history of these patients may be less morbid than invasive therapies. Available treatments include observation, surgical resection, endovascular embolization, stereotactic radiosurgery, or combination thereof. Knowing the risk factors for bAVM hemorrhage is crucial for selecting appropriate therapeutic strategies. In this review, we discussed several biological risk factors, which may contribute to bAVM hemorrhage.

Acute Subdural Hematomas in Ruptured Brain Arteriovenous Malformations: Association with Distal Flow-Related Aneurysms

PURPOSE

Non-traumatic acute subdural hematomas (SDH) are rare and have seldom been reported in ruptured brain arteriovenous malformations (BAVM). The aim of this study was to report the frequency of acute SDH in BAVM-related hemorrhage and to determine the relationship of SDHs with BAVM angioarchitectural features.

METHODS

This was a retrospective monocentric study of patients admitted for BAVM rupture between 2003 and 2017. Patients with rupture complicating or closely following partial embolization procedures were excluded. Univariate followed by multivariate logistic regression analysis was used to determine factors significantly and independently associated with SDHs and distal flow-related aneurysms.

RESULTS

A total of 181 patients with 188 BAVM ruptures admitted during the study period were included, eleven cases of acute SDH were identified (6%) and 2 cases of isolated SDH were found. The presence of a distal flow-related aneurysm was the only feature independently and significantly associated with SDH (odds ratio [OR] 8.1, 95% confidence interval, CI 1.9-34.5, P = 0.003). Distal flow-related aneurysms were associated with proximal flow-related aneurysms (OR 28, 95%CI 4.9-163.8, P < 0.001), were more frequent in infratentorial BAVMs (OR 3.7, 95%CI 1.3-10.2, P = 0.01) and more often found in cases of acute SDH (OR 16.9, 95%CI 3.6-79.6, P < 0.001) and subarachnoid hemorrhage (SAH) (OR 4.5, 95%CI 1.7-12.2, P = 0.003).

CONCLUSION

Ruptured BAVMs can rarely present with acute SDH and SDH in ruptured BAVMs are often associated with distal flow-related aneurysms. This finding may impact acute management of ruptured BAVMs with SDH by eliciting an emergent and thorough imaging work-up to identify distal flow-related aneurysm(s), in turn leading to treatment.

Hemodynamics Associated With Intracerebral Arteriovenous Malformations: The Effects of Treatment Modalities

The understanding of the physiology of cerebral arteriovenous malformations (AVMs) continues to expand. Knowledge of the hemodynamics of blood flow associated with AVMs is also progressing as imaging and treatment modalities advance. The authors present a comprehensive literature review that reveals the physical hemodynamics of AVMs, and the effect that various treatment modalities have on AVM hemodynamics and the surrounding cortex and vasculature. The authors discuss feeding arteries, flow through the nidus, venous outflow, and the relative effects of radiosurgical monotherapy, endovascular embolization alone, and combined microsurgical treatments. The hemodynamics associated with intracranial AVMs is complex and likely changes over time with changes in the physical morphology and angioarchitecture of the lesions. Hemodynamic change may be even more of a factor as it pertains to the vast array of single and multimodal treatment options available. An understanding of AVM hemodynamics associated with differing treatment modalities can affect treatment strategies and should be considered for optimal clinical outcomes.

In-room assessment of intravascular velocity from time-resolved rotational angiography in patients with arteriovenous malformation: a pilot study

Background

Time-resolved rotational angiography (t-RA) enables interventionists to better comprehend complex arteriovenous malformations (AVMs), thereby facilitating endovascular treatment. However, its use in evaluating hemodynamic changes has rarely been explored.

Objective

This study uses t-RA to estimate intravascular flow in patients with AVM to compare this with flow in the normal population.

Methods

Patients with available t-RA scans were prospectively categorized into one of three groups: hemorrhagic AVM, non-hemorrhagic AVM and control. Pulsatile time–density curves (TDCs) for C1, C6 and VOIMCA were used for amplitude and velocity estimation. C1 was at the cervical internal carotid artery (ICA), 2–3 cm below the carotid canal, C6 was at the paraclinoid segment of the ICA, and VOIMCA was at the junction of the first and second segment of the middle cerebral artery (MCA). A waveform amplitude ratio was defined as (peak − trough)/trough contrast intensity. VICA was defined as the distance between C6 and C1 divided by the time required for the wave to pass, and correspondingly, the average velocity of MCA (VMCA) was defined as the distance between C6 and VOIMCA divided by the duration for the same peak to travel from C6 and VOIMCA, AVM volume was estimated by MR angiography.

Results

Amplitude ratios AC1 and AC6, and average flow velocities VICA and VMCA were significantly larger in the non-hemorrhagic group than in the control group, while the hemorrhagic AVM group was not significantly different from the controls. VICA and VMCA showed moderate to good correlations with AVM volume (r=0.51 and 0.73, respectively). VMCA (33.0±9.1) was significantly lower than VICA (41.3±13.2) in the control group, but not in the two AVM groups.

Conclusion

TDC waveform propagation derived from t-RA can quantify hemodynamic differences between AVM and the control group. t-RA provides both real-time anatomic and hemodynamic evaluation, and can thus potentially improve the interventional workflow.

Early Rebleeding after Brain Arteriovenous Malformation Rupture, Clinical Impact and Predictive Factors: A Monocentric Retrospective Cohort Study

Background: Brain arteriovenous malformations (BAVMs) are a leading cause of intracranial hemorrhage in young adults. This study aimed to identify individual predictive factors of early rebleeding after BAVM rupture and determine its impact on prognosis. Methods: Early rebleeding was defined as a spontaneous intracranial hemorrhage within 30 days of BAVM rupture in patients with nonobliterated BAVMs. One hundred fifty one patients with 158 BAVM hemorrhagic events admitted to a tertiary care center during 14 years were included. Univariate followed by multivariate logistic regression was performed to assess the impact of early rebleeding on in-hospital mortality and modified Rankin Scale (mRS) score beyond 3 months and to identify independent predictors of early rebleeding. Results: Eight early rebleeding events were observed, 6 of which occurred during the first 7 days. Early rebleeding was independently and significantly associated with poor outcome (mRS ≥3 beyond 3 months, p = 0.004) but not with in-hospital mortality (p = 0.9). Distal flow-related aneurysms (p = 0.009) and altered consciousness with a Glasgow coma scale score of 3 (p = 0.01) were independently associated with early rebleeding. Conclusions: Early rebleeding is a severe complication that can occur after BAVM-related hemorrhage. Distal flow-related aneurysms and initial altered consciousness are associated with early rebleeding.

The Hemodynamic Changes in Patients with Cerebral Arteriovenous Malformations before and after Interventional Embolization Therapy with Glubran 2 Acrylic Glue

The study explored hemodynamic changes in patients with cerebral arteriovenous malformations (CAVM) before and -after interventional embolization therapy with Glubran 2 acrylic glue and analyzed the related factors. CAVM patients received endovascular embolization therapy with Glubran 2. Patients' systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), blood flow velocity (BFV), and pulsatility index (PI) were measured. The location of malformed vessels, Spetzler-Martin (SM) grade, CAVM size, and type of feeding artery and venous drainage were analyzed. CAVM patients showed increased DBP, SBP, MAP, and PI and decreased average BFV compared to before therapy. CAVM patients with big CAVM size, SM grade IV/V, deep location malformed vessels, deep, and mixed venous drainage, and cortical branch and mixed artery blood-supply exhibited lower DBP, SBP, MAP, and PI but higher average BFV. Hypertensive CAVM patients showed lower DBP, SBP, MAP, average BFV, and PI before or after embolization. Hypertension, SM grade, CAVM size, malformed vessels location, venous drainage, and artery blood-supply were correlated to the hemodynamic changes of CAVM patients. Embolization with Glubran 2 acrylic glue could enhance hemodynamics in CAVM patients, and the hemodynamic changes were in correlation with the SM grade, CAVM size, and malformed vessels location.

Delayed Venous Drainage in Ruptured Arteriovenous Malformations Based on Quantitative Color-Coded Digital Subtraction Angiography

OBJECTIVE

Clinically applicable hemodynamic risk factors to predict arteriovenous malformation (AVM) rupture are missing in the literature. The aim of this study was to use catheter angiography to identify hemodynamic parameters in ruptured and unruptured AVMs.

METHODS

Patients with frontal and temporal AVMs and Siemens syngo iFlow color-coding angiography were included in this study (n = 71). Clinical and radiologic data (age, sex, Spetzler-Martin [SM] and supplemented SM grade, and rupture status), and hemodynamic features (contrast mean transit time [MTT] of feeding arteries, draining veins, AVM nidus, and the cerebral circulation time [CCT]) were analyzed. Univariable analysis was performed to compare findings between ruptured and unruptured AVMs.

RESULTS

In total, 35 ruptured and 36 unruptured AVMs were analyzed. Clinical characteristics and AVM grades were comparable between ruptured and unruptured AVMs. Ipsilateral CCT (5.2 vs. 4.0 seconds; P = 0.035), MTT between Tmax of the ipsilateral internal carotid artery and Tmax of sinus entry of the draining vein (3.2 vs. 2.0 seconds; P < 0.001), and MTT between Tmax at the start of venous outflow and Tmax of sinus entry (1.6 vs. 0.7 seconds; P < 0.0001) were significantly longer in ruptured compared with unruptured AVMs. MTTs of nidus, between the internal carotid and feeding arteries, of the venous sinus passage as well as contralateral CCT and controlled ipsilateral CCT were comparable between both groups.

CONCLUSIONS

Ruptured AVMs have significantly prolonged venous drainage times compared with unruptured AVMs; this suggests restricted AVM drainage and increased blood pressure within the AVM nidus. Prospective studies are needed to determine the predictive power of these measurements.

Subsequent haemorrhage in children with untreated brain arteriovenous malformation: Higher risk with unbalanced inflow and outflow angioarchitecture

OBJECTIVES

Children with brain arteriovenous malformations (bAVMs) are at risk of life-threatening haemorrhage in their early lives. Our aim was to analyse various angioarchitectural features of bAVM to predict the risk of subsequent haemorrhage during follow-up in children.

METHODS

We identified all consecutive children admitted to our institution for bAVMs between July 2009 and September 2015. Children with at least 1 month of treatment-free follow-up after diagnosis were included in further analysis. Annual rates of AVM rupture as well as several potential risk factors for subsequent haemorrhage were analysed using Kaplan-Meier analyses and Cox proportional hazards regression models.

RESULTS

We identified 110 paediatric patients with a mean follow-up period of 2.1 years (range, 1 month-15.4 years). The average annual risk of haemorrhage from untreated AVMs was 4.3 % in children. No generalised venous ectasia in conjunction with fast arteriovenous shunt was predictive of subsequent haemorrhage (RR, 7.55; 95 % CI 1.96-29.06). The annual rupture risk was 11.1 % in bAVMs without generalised venous ectasia but with fast arteriovenous shunt.

CONCLUSIONS

bAVM angiographic features suggesting unbalanced inflow and outflow might be helpful to identify children at higher risk for future haemorrhage.

KEY POINTS

• Haemorrhage risk stratification is important for children with untreated brain AVM. • Angiographic features suggesting unbalanced inflow and outflow predict paediatric brain AVM haemorrhage. • Identifying AVMs with high rupture risk help patient selection and tailoring treatment.

Feasibility of Quantification of Intracranial Aneurysm Pulsation with 4D CTA with Manual and Computer-Aided Post-Processing

Background and Purpose

The analysis of the pulsation of unruptured intracranial aneurysms might improve the assessment of their stability and risk of rupture. Pulsations can easily be concealed due to the small movements of the aneurysm wall, making post-processing highly demanding. We hypothesized that the quantification of aneurysm pulsation is technically feasible and can be improved by computer-aided post-processing.

Materials and Methods

Images of 14 cerebral aneurysms were acquired with an ECG-triggered 4D CTA. Aneurysms were post-processed manually and computer-aided on a 3D model. Volume curves and random noise-curves were compared with the arterial pulse wave and volume curves were compared between both post-processing modalities.

Results

The aneurysm volume curves showed higher similarity with the pulse wave than the random curves (Hausdorff-distances 0.12 vs 0.25, p<0.01). Both post-processing methods did not differ in intra- (r = 0.45 vs r = 0.54, p>0.05) and inter-observer (r = 0.45 vs r = 0.54, p>0.05) reliability. Time needed for segmentation was significantly reduced in the computer-aided group (3.9 ± 1.8 min vs 20.8 ± 7.8 min, p<0.01).

Conclusion

Our results show pulsatile changes in a subset of the studied aneurysms with the final prove of underlying volume changes remaining unsettled. Semi-automatic post-processing significantly reduces post-processing time but cannot yet replace manual segmentation.

Relationship of pulsatility and resistance indices to cerebral arteriovenous malformation angioarchitectural features and hemorrhage

The role that hemodynamics plays in the pathophysiology of cerebral arteriovenous malformation (AVM) hemorrhage remains unclear. Here, we examine the relationship of pulsatility and resistance indices to AVM angioarchitectural features and hemorrhage. Records of patients with cerebral AVMs evaluated at our institution between 2007-2014 and with flows obtained before treatment using quantitative magnetic resonance angiography (QMRA) were retrospectively reviewed. Flow volume rate and flow velocity were measured in primary arterial feeders and compared to their contralateral counterparts. Pulsatility index (PI)=[(systolic flow velocity-diastolic flow velocity)/mean flow velocity] and resistance index (RI)=[(systolic flow velocity-diastolic flow velocity)/systolic flow velocity] were calculated for each feeder and compared to the normal contralateral vessel. Relationships between PI, RI and AVM clinical and angioarchitectural features were assessed using linear regression. Seventy-two patients with a total of 101 feeder arteries were included. PI and RI were significantly lower in AVM arterial feeders compared to normal vessels, thereby resulting in significantly higher flow volume rates and flow velocities in feeder vessels. There was no significant association of PI and RI with hemorrhagic presentation, exclusive deep venous drainage, venous stenosis, single draining vein, or deep location. In conclusion, PI and RI can be measured using QMRA and are lower in AVM arterial feeders compared to normal vessels. Although we found no significant correlation between PI, RI, and AVM angioarchitectural characteristics thought to be associated with increased hemorrhage risk, future studies with larger sample sizes may better elucidate this relationship.

Aneurysms Associated with Brain Arteriovenous Malformations

Brain arteriovenous malformations are frequently associated with the presence of intracranial aneurysms at a higher-than-expected incidence based on the frequency of each lesion individually. The identification of intracranial aneurysms in association with AVMs has increased due to improvement in diagnostic techniques, particularly 3D and superselective conventional angiography. Intracranial aneurysms may confer a higher risk of hemorrhage at presentation and of rehemorrhage in patients with AVMs and therefore may be associated with a more unfavorable natural history. The association of AVMs and intracranial aneurysms poses important therapeutic challenges for practicing neurosurgeons, neurologists, and neurointerventional radiologists. In this report, we review the classification and radiology of AVM-associated intracranial aneurysms and discuss their clinical significance and implications for treatment.

Evaluation of 4D vascular flow and tissue perfusion in cerebral arteriovenous malformations: influence of Spetzler-Martin grade, clinical presentation, and AVM risk factors

BACKGROUND AND PURPOSE

The role of intracranial hemodynamics in the pathophysiology and risk stratification of brain AVMs remains poorly understood. The purpose of this study was to assess the influence of Spetzler-Martin grade, clinical history, and risk factors on vascular flow and tissue perfusion in cerebral AVMs.

MATERIALS AND METHODS

4D flow and perfusion MR imaging was performed in 17 patients with AVMs. Peak velocity and blood flow were quantified in AVM feeding and contralateral arteries, draining veins, and the straight sinus. Regional perfusion ratios (CBF, CBV, and MTT) were calculated between affected and nonaffected hemispheres.

RESULTS

Regarding flow parameters, high-grade AVMs (Spetzler-Martin grade of >2) demonstrated significantly increased peak velocity and blood flow in the major feeding arteries (P < .001 and P = .004) and straight sinus (P = .003 and P = .012) and increased venous draining flow (P = .001). The Spetzler-Martin grade significantly correlated with cumulative feeding artery flow (r = 0.85, P < .001) and draining vein flow (r = 0.80, P < .001). Regarding perfusion parameters, perinidal CBF and CBV ratios were significantly lower (P < .001) compared with the remote ratios and correlated negatively with cumulative feeding artery flow (r = -0.60, P = .014 and r = -0.55, P = .026) and draining vein flow (r = -0.60, P = .013 and r = -0.56, P = .025). Multiple regression analysis revealed no significant association of AVM flow or perfusion parameters with clinical presentation (rupture and seizure history) and AVM risk factors.

CONCLUSIONS

Macrovascular flow was significantly associated with increasing Spetzler-Martin grade and correlated with perinidal microvascular perfusion in cerebral AVMs. Future longitudinal studies are needed to evaluate the potential of comprehensive cerebral flow and perfusion MR imaging for AVM risk stratification.

Advances and innovations in brain arteriovenous malformation surgery

Arteriovenous malformations (AVMs) of the brain are very complex and intriguing pathologies. Since their initial description by Luschka and Virchow in the middle of the 19th century, multiple advances and innovations have revolutionized their management and surgical treatment. Here, we review the historical landmarks in the surgical treatment of AVMs and then illustrate the most recent and futuristic technologies aiming to improve outcomes in AVM surgeries. In particular, we examine potential advances in patient selection, imaging, surgical technique, neuroanesthesia, and postoperative neuro-rehabilitation and quantitative assessments. Finally, we illustrate how concurrent advances in radiosurgery and endovascular techniques might present new opportunities to treat AVMs more safely from a surgical perspective.

Aligning 3D time-of-flight MRA datasets for quantitative longitudinal studies: evaluation of rigid registration techniques

OBJECTIVE

3D Time-of-flight (TOF) magnetic resonance angiography is commonly used for vascular analyses. A quantification of longitudinal morphological changes usually requires the registration of TOF image sequences acquired at different time points. The aim of this study was to evaluate the precision of different 3D rigid registration setups such that an optimal quantification of morphological changes can be achieved.

METHODS

Eight different rigid registration techniques were implemented and evaluated in this study using the target registration error (TRE) calculated based on 554 landmarks defined in twenty TOF datasets. The registration techniques differed in integration of brain and vessel segmentation masks and usage of a multi-resolution framework. Furthermore, the benefit of a prior volume-of-interest definition for registration accuracy was evaluated.

RESULTS

The results revealed that the highest registration accuracies can be achieved using a multi-resolution framework and a cerebrovascular segmentation as mask. Numerically, a mean TRE of 1.1mm was calculated. If applicable, a prior definition of a volume-of-interest allows a reduction of the TRE to only 0.6mm.

CONCLUSION

TOF datasets should be registered using vessel segmentations as mask, multi-resolution framework and previous volume-of-interest definition if possible to obtain the highest registration precision. This is especially the case for longitudinal datasets that are separated by several months while the registration technique seems less important for datasets that are only separated by a few days.

Secondary histomorphological changes in cerebral arteries of normotensive and hypertensive rats following a carotid-jugular fistula induction

Haemodynamic changes in cerebral circulation are associated with the natural ageing process and associated pathology, leading to the development of incapacitating neurological and neurovascular diseases. Due to inherent biological limitations, current literatures mostly aimed at studying the correlation descriptively or quantifying the relationship in vitro or using computational models. In this paper, a model of a carotid-jugular fistula in the rat was used to create a haemodynamic insult to the intracranial arterial circulation and subsequent venous drainage. An arterial-venous (AV) fistula was created in 12 rats, 6 of which are normotensive Wistar-Kyoto strain (WKY) and the rest spontaneously hypertensive strain (SHR) with an additional 6 in each strains designed as controls without previous surgery. After 4 weeks of convalescence, all 24 rats were euthanised and their cerebral circulation was examined histomorphologically. We confirmed an intrinsic morphological difference between normotensive WKY and hypertensive SHR and found a modest but significant arterial shrinkage in both strains induced with AV fistula. We also reported that alterations in blood flow are also associated with marked extracellular matrix changes. We concluded that the model was suitable for studying the relative contributions of altering haemodynamic patterns and venous drainage on cerebrovascular changes. We also found that hypertension modulated cerebral vascular changes in addition to disrupted blood flow.

Computer-aided nidus segmentation and angiographic characterization of arteriovenous malformations

PURPOSE

Exact knowledge about the nidus of an arteriovenous malformation (AVM) and the connected vessels is often required for image-based research projects and optimal therapy planning. The aim of this work is to present and evaluate a computer-aided nidus segmentation technique and subsequent angiographic characterization of the connected vessels that can be visualized in 3D.

METHODS

The proposed method was developed and evaluated based on 15 datasets of patients with an AVM. Each dataset consists of a high-resolution 3D and a 4D magnetic resonance angiography (MRA) image sequence. After automatic cerebrovascular segmentation from the 3D MRA dataset, a voxel-wise support vector machine classification based on four extracted features is performed to generate a new parameter map. The nidus is represented by positive values in this parameter map and can be extracted using volume growing. Finally, the nidus segmentation is dilated and used for an automatic identification of feeding arteries and draining veins by integrating hemodynamic information from the 4D MRA datasets.

RESULTS

A quantitative comparison of the computer-aided AVM nidus segmentation results to manual gold-standard segmentations by two observers revealed a mean Dice coefficient of 0.835, which is comparable to the inter-observer agreement for which a mean Dice coefficient of 0.830 was determined. The angiographic characterization was visually rated feasible for all patients.

CONCLUSION

The presented computer-aided method enables a reproducible and fast extraction of the AVM nidus as well as an automatic angiographic characterization of the connected vessels, which can be used to support image-based research projects and therapy planning of AVMs.