Feeding artery pressure and venous drainage pattern are primary determinants of hemorrhage from cerebral arteriovenous malformations

Multi-Stage Treatment for Spetzler-Martin Grades III, IV, and V Arteriovenous Malformations: Preoperative Embolization and Microsurgical Resection in a Consecutive Series of 250 Patients

PURPOSE

The treatment of high-grade brain AVMs is challenging and has no guidelines available to date. This study was aimed at reporting the experience of two centers in treating these AVMs through a multi-stage approach consisting of preoperative embolization and microsurgical resection.

METHODS

A retrospective review was performed for 250 consecutive patients with a diagnosis of high-grade brain AVM (Spetzler-Martin grades III, IV, and V) treated in two centers in Germany between January 1989 and February 2023. The analyzed data included demographic, clinical, morphological, and neurological data.

RESULTS

A total of 150 cases (60%) were classified as Spetzler-Martin grade III, 82 cases (32.8%) were classified as grade IV, and 18 cases (7.2%) were classified as grade V. Eighty-seven cases (34.8%) presented with hemorrhage. The devascularization percentages achieved were <50% in 24 (9.6%), 50-80% in 55 (22%), and >80% in 171 (68.4%) cases. The average number of sessions was 5.65 ± 5.50 and 1.11 ± 0.32 endovascular and surgical procedures, respectively, and did not significantly differ by rupture status. Death or dependency (mRS score ≥ 3) after the last follow-up was observed in 18.8% of patients and was significantly associated with age > 80 years and poor baseline neurological condition. The complete resection rate was 82.3% and was significantly associated with age > 80 years, large nidus, and deep venous drainage. Permanent disabling neurological deficit after at least 3 months of follow-up was diagnosed in 13.2% of patients and was significantly associated with age > 80 years and infratentorial locations.

CONCLUSION

A multi-stage treatment for high-grade AVMs is feasible for selected cases but comes at a functional cost. The devascularization percentage was not associated with the investigated outcomes. Age > 80 years was associated with poor safety and effectiveness outcomes; consequently, this treatment should be offered only in exceptional circumstances.

Hemodynamic and Anatomical Factors in Arteriovenous Malformation Clinical Presentation: 45 Case Studies

BACKGROUND

Hemodynamic factors have been implicated in hemorrhage from cerebral arteriovenous malformations (AVMs). The goal of this endovascular study is to analyze the hemodynamic variability in AVM feeders in a balanced group of ruptured and unruptured AVMs of various sizes and at both superficial and deep locations.

METHODS

We monitored feeder artery pressure (FP) using microcatheters in 45 patients with AVMs (16 with hemorrhage, 29 without) during superselective angiography and AVM embolization.

RESULTS

Mean FP was 49 mm Hg. Significant determinants of FP were the systemic pressure (p < 0.001), AVM size (p = 0.03), and the distance of the microcatheter tip from the Circle of Willis (p = 0.06), but not the presence of hemorrhage, patient age, or feeder artery diameter. The FP in ruptured AVMs was 7 mm Hg higher than in unruptured ones (53.8 mm Hg vs. 47.1 mm Hg, p = 0.032). The presence or absence of venous outflow stenosis and the position of the AVM nidus (superficial or deep to the cortical surface) were important anatomical predictors of AVM presentation.

CONCLUSION

The pressure in the feeding artery supplying an AVM is the result of factors which include the systemic arterial pressure, the size of the AVM nidus, and the distance of the AVM from the Circle of Willis. The correlation between these variables makes it difficult to study the risk of hemorrhage as a function of a single factor, which may account for the variation in the conclusions of previous studies.

Molecular and genetic mechanisms in brain arteriovenous malformations: new insights and future perspectives

Brain arteriovenous malformations (bAVMs) are rare vascular lesions made of shunts between cerebral arteries and veins without the interposition of a capillary bed. The majority of bAVMs are asymptomatic, but some may be revealed by seizures and potentially life-threatening brain hemorrhage. The management of unruptured bAVMs remains a matter of debate. Significant progress in the understanding of their pathogenesis has been made during the last decade, particularly using genome sequencing and biomolecular analysis. Herein, we comprehensively review the recent molecular and genetic advances in the study of bAVMs that not only allow a better understanding of the genesis and growth of bAVMs, but also open new insights in medical treatment perspectives.

Is there an Influence of Match and Mismatch of Venous Drainage Pattern on AVM Hemorrhagic Presentation?

Objective

To analyze whether there is an influence of match and mismatch of venous drainage patterns on arteriovenous malformation (AVM) hemorrhagic presentation.

Methods

Consecutive 161 patients of AVM between 2014 and 2017 were retrospectively reviewed. Venous drainage was considered deep or superficial. Match of venous drainage pattern was defined as a superficial AVM with only superficial venous drainage or a deep AVM with deep venous drainage. Mismatch of venous drainage pattern was defined as a superficial AVM involving a deep venous drainage. Univariate analysis was used to assess the influence of match and mismatch of venous drainage pattern on AVM hemorrhagic presentation.

Results

AVM location and venous drainage were matched in 116 patients, including superficial location with superficial venous drainage or deep location with deep venous drainage, and were mismatched in 45 patients, including superficial location with deep venous drainage. The rupture proportion of mismatch venous drainage pattern was statistically comparable to that of deep location with deep drainage (P = 0.819). However, superficial location with deep venous drainage was statistically associated with a higher rupture percentage than that of superficial location with superficial venous drainage (P = 0.003).

Conclusions

Mismatch venous drainage pattern or an exclusively deep venous drainage is associated with an initial clinical presentation with an AVM hemorrhage.

Correlation between angioarchitectural characteristics of brain arteriovenous malformations and clinical presentation of 183 patients

BACKGROUND

The correlation between angioarchitecture and clinical presentation of brain arteriovenous malformation (bAVM) remains a subject of debate.

OBJECTIVE

The main purpose of the present study was to assess the correlation between angioarchitectural characteristics of bAVM and clinical presentation.

METHODS

A retrospective review of all consecutive patients presenting a bAVM who underwent a cerebral angiography at Beneficencia Portuguesa Hospital in São Paulo between January 2006 and October 2016 was carried out. Patients were divided in five groups: group 1 - hemorrhage; group 2 - seizure; group 3 - headache; group 4 - progressive neurological deficits (PND); group 5 - incidental).

RESULTS

A total of 183 patients were included, with group 1 comprising 56 cases, group 2 49 cases, group 3 41 cases, group 4 28 cases, and group 5 9 cases. Regarding hemorrhage presentation, a statistical correlation was observed with female gender (P < 0.02), Spetzler-Martin 3B (P < .0015), and lesions with low flow (P < 0.04). A positive association was found between group 2 and age less than 36 years (P < 0.001), male sex (P < 0.018), presence of superficial lesions not classified as SM 3B (P < 0.002), presence of venous ectasia (p <0.03), and arterial steal phenomenon (P < 0.03). Group 4 was associated with older age (P < 0.01).

CONCLUSIONS

Angioarchitectural characteristics can be correlated with some clinical presentations as well as with some clinical data, making it possible to create predictive models to differentiate clinical presentations.

Possible Association Between Rupture and Intranidal Microhemodynamics in Arteriovenous Malformations: Phase-Contrast Magnetic Resonance Angiography-Based Flow Quantification

OBJECTIVE

To examine a potential association between intranidal microhemodynamics and rupture using a phase-contrast magnetic resonance angiography (PCMRA)-based flow quantification technique in arteriovenous malformations (AVMs).

METHODS

We retrospectively collected data on 30 consecutive patients with AVMs (23 unruptured and 7 ruptured). Based on PCMRA data, maximal (V_max) and mean (V_mean) intranidal velocities were calculated. Logistic regression analysis was performed to assess factors associated with previous AVM rupture.

RESULTS

All ruptures occurred within 6 months before PCMRA. The mean nidus volume was 4.7 mL. Eleven patients (37%) had deep draining vein(s), and 6 patients (20%) had a deep-seated nidus. The mean ± standard deviation V_mean and V_max were 9.6 ± 2.8 cm/second and 66.7 ± 26.2 cm/second, respectively. The logistic regression analyses revealed that higher V_max (P = 0.075, unit odds ratio [OR] = 1.05, 95% confidence interval [95% CI] = 1.00-1.10) was significantly associated with prior hemorrhage. The receiver-operating curve analyses demonstrated that a V_mean of 10.8 cm/second (area under the curve = 0.671) and V_max of 90.2 cm/second (area under the curve = 0.764) maximized the Youden Index. A V_max > 90 cm/second was significantly associated with AVM rupture both in the univariate (P = 0.025, OR = 9.0, 95% CI = 1.3-61.1) and multivariate (P = 0.008, OR = 51.7, 95% CI = 2.8-968.3) analyses.

CONCLUSIONS

Presence of faster velocities in intranidal vessels may suggest aberrant microhemodynamics and thus be associated with AVM rupture. PCMRA-based velocimetry seems to be a promising tool to predict future AVM rupture.

Intra-aneurysmal pressure changes during stent-assisted coiling

We aimed to examine aneurysm hemodynamics with intra-saccular pressure measurement, and compare the effects of coiling, stenting and stent-assisted coiling in proximal segments of intracranial circulation. A cohort of 45 patients underwent elective endovascular coil embolization (with or without stent) for intracranial aneurysm at our department. Arterial pressure transducer was used for all measurements. It was attached to proximal end of the microcatheter. Measurements were taken in the parent artery before and after embolization, at the aneurysm dome before embolization, after stent implantation, and after embolization. Stent-assisted coiling was performed with 4 different stents: LVIS and LVIS Jr (Microvention, Tustin, CA, USA), Leo (Balt, Montmorency, France), Barrel VRD (Medtronic/ Covidien, Irvine, CA, USA). Presence of the stent showed significant reverse correlation with intra-aneurysmal pressure–both systolic and diastolic—after its implantation (r = -0.70 and r = -0.75, respectively), which was further supported by correlations with stent cell size–r = 0.72 and r = 0.71, respectively (P<0.05). Stent implantation resulted in significant decrease in diastolic intra-aneurysmal pressure (p = 0.046). Systolic or mean intra-aneurysmal pressure did not differ significantly. Embolization did not significantly change the intra-aneurysmal pressure in matched pairs, regardless of the use of stent (p>0.05). In conclusion, low-profile braided stents show a potential to divert blood flow, there was significant decrease in diastolic pressure after stent placement. Flow-diverting properties were related to stent porosity. Coiling does not significantly change the intra-aneurysmal pressure, regardless of packing density.

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.

Embolized cerebral arteriovenous malformations: a multivariate analysis of 101 excised specimens

OBJECTIVE

Endovascular approaches have evolved from a technique practiced at very few centers to a widely available option in the management of arteriovenous malformations (AVMs) of the central nervous system. Embolization can be employed as definitive therapy or as an adjunct to surgical excision. A wide variety of embolic agents have been successfully developed and used in the clinical setting. In addition to facilitating vascular occlusion, embolic agents induce a number of reactive and destructive changes in vessel walls and the surrounding tissue. However, studies examining the pathological changes induced by different embolic agents and varying times of exposure are scarce. The goal of the present study was to compare embolic agents and time of exposure on the pathology in excised specimens.

METHODS

The records of the Department of Pathology at the London Health Sciences Centre were searched for embolized AVMs for the 35-year period 1980–2015. All cases were reevaluated for clinical and technical variables and standardized histopathological findings. Cases were grouped by embolic agent, volume of agent used, and time to excision.

RESULTS

A total of 101 specimens were identified. Embolic agents were invariably associated with a range of pathological findings, some of which may affect the integrity of vessel walls or the reestablishment of flow, thrombosis, acute and chronic inflammatory changes, angionecrosis, extravasation, and recanalization. The type of embolic agent did not predict differences in the incidence or severity of histopathological changes. Larger volumes of embolic agent were associated with a greater proportion of vessels containing embolic material. AVMs excised early (< 1 week postembolization) contained more acute vasculitis, while those excised later (≥ 1 week postembolization) were more likely to exhibit recanalization and foreign body giant cell infiltrates.

CONCLUSIONS

Embolic agents induce a predictable range and temporal progression of pathological changes in cerebral AVMs. The embolic agents studied are indistinguishable in terms of the range and frequency of pathological reactions induced. Greater volumes of embolic agent are associated with more abundant agent within the lesion, but the proportion of vessels and vascular cross-sectional areas containing agent is small. Several changes are significantly associated with time postembolization. Acute vasculitis is a more common finding in the 1st week, while recanalization and foreign body–type granulomatous inflammation are more common at 1 week and beyond.

Differences in Pressure Within the Sac of Human Ruptured and Nonruptured Cerebral Aneurysms

BACKGROUND

Hemodynamics plays a critical role in the development, growth, and rupture of intracranial aneurysms. This data could be vital in determining individual aneurysm rupture risk and could facilitate our understanding of aneurysms.

OBJECTIVE

To present the largest prospective cross-sectional cohort study of intrasaccular pressure recordings of ruptured and nonruptured intracranial aneurysms and describe the hemodynamic differences that exist between ruptured and nonruptured aneurysms.

METHODS

During endovascular treatment, a standard 1.8-Fr 200 m length microcatheter was navigated into the dome of the aneurysm prior to coil embolization. With the microcatheter centralized within the dome of the aneurysm, an arterial pressure transducer was attached to the proximal end of the microcatheter to measure the stump pressure inside the aneurysm dome.

RESULTS

In 68 aneurysms (28 ruptured, 40 nonruptured), we observed that ruptured cerebral aneurysms had a lower systolic and mean arterial pressure compared to nonruptured cohort (P = .0008). Additionally, the pulse pressures within the dome of ruptured aneurysms were significantly more narrow than that of unruptured aneurysms (P = .0001). These findings suggest that there may be an inherent difference between ruptured and nonruptured aneurysms and such recordings obtained during routine digital subtraction angiography could potentially become a widely applied technique to augment risk stratification of aneurysms.

CONCLUSION

Our preliminary data present new evidence distinguishing ruptured from unruptured aneurysms that may have a critical role as a predictive parameter to stratify the natural history of nonruptured intracranial aneurysms and as a new avenue for future investigation.

Grades of brain arteriovenous malformations and risk of hemorrhage and death

Objective

To assess the relationship of the grade of unruptured and untreated Brain Arteriovenous Malformations (AVMs), with the risk of subsequent stroke and death during follow‐up.

Methods

This prospective study was drawn from a cohort of adult patients with unruptured AVMs, who participated in the conservative treatment arm (medical management only for headache or seizures) of the randomized clinical trial of unruptured brain AVMs (ARUBA study). The grade of AVMs (Spetzler–Martin scale) was dichotomized into categories: AVMs of grades I and II were considered low grade; AVMs of grades III and IV were considered high grade. There were no grade V AVM patients in ARUBA. The primary outcome was symptomatic stroke (hemorrhagic or ischemic – documented by imaging) or death.

Results

The conservative treatment group had 123 patients (“as treated” analysis). 71 (57.7%) had lesions characterized for this analysis as low‐grade lesions and 52 (42.2%) as high grade. From the total of 10 (8.13%) primary outcomes, three occurred (4.22%) in low‐grade AVMs and seven (13.46%) in high‐grade AVMs (P = 0.0942).

Interpretation

Statistical analysis of the cohort of patients with unruptured and untreated AVMs from ARUBA study showed that the graduation categories (Spetzler–Martin grades) were not associated with the outcome of subsequent stroke or death.

Reperfusion Changes After Stroke and Practical Approaches for Neuroprotection

Reperfusion is the first line of care in a growing number of eligible acute ischemic stroke patients. Early reperfusion with thrombolytic drugs and endovascular mechanical devices is associated with improved outcome and lower mortality rates compared with natural history. Reperfusion is not without risk, however, and may result in reperfusion injury, which manifests in hemorrhagic transformation, brain edema, infarct progression, and neurologic worsening. In this article, the functional and structural changes and underlying molecular mechanisms of ischemia and reperfusion are reviewed. The pathways that lead to reperfusion injury and novel neuroprotective strategies with endogenous properties are discussed.

Transvenous embolization of arteriovenous malformations

Embolization of arteriovenous malformations is characteristically used as part of a multimodal treatment approach, pre-operatively to facilitate microsurgical resection or as a preradiosurgical adjunct. The concept of AVM cure via embolization alone has gained popularity in recent years. Embolization of AVMs has been most commonly performed transarterially, with the transvenous route traditionally eschewed given concern over precipitating premature venous occlusion and consequent hemorrhage. However, the transvenous approach in treating AVMs offers several distinct advantages compared to the transarterial route and can be used in instances when the latter is not feasible, with several series having proven its efficacy and safety. Conceptually, AVM embolization performed via the transvenous route achieves complete obliteration by directly and facilely targeting the nidus. Nidal embolisate penetration is facilitated by control of arterial inflow via systemic or local hypotension. Innovation in endovascular strategies has led to significantly improved obliteration rates. The experience with transvenous AVM embolization is reviewed and discussed.

Curative Transvenous Embolization for Ruptured Brain Arteriovenous Malformations: A Single-Center Experience from China

OBJECTIVE

To evaluate feasibility and safety of transvenous embolization for brain arteriovenous malformations (AVMs).

METHODS

Between November 2016 and August 2017, a transvenous endovascular embolization protocol was implemented at the Henan Provincial People's Hospital for consecutive patients with ruptured brain AVMs. Therapeutic decision making was based on Spetzler-Martin grade, brain AVM location, pattern of venous drainage, and angioarchitecture. Transvenous embolization was combined with transarterial support. Complete angiographic obliteration of the nidus was the objective of treatment.

RESULTS

Among 10 patients with ruptured brain AVMs, 8 were male. Spetzler-Martin grades before transvenous embolization were IV in 3 patients, III in 5 patients, II in 1 patient, and I in 1 patient. Modified Rankin Scale score before the procedure was 0-2 for 6 of 10 patients. Five patients also had deep venous drainage. Arterial blood pressure control and venous pressure cooker technique were used in all 10 patients; 9 patients had immediate angiographic occlusion. Two patients had a ventricular hemorrhage, which did not cause any disability after medical treatment. Seven patients underwent angiography 3-5 months after the procedure, and complete obliteration of the nidus was confirmed. Median clinical follow-up for all 10 patients was 8 months (range, 3-12 months). Epilepsy occurred in 1 patient 3 months after the procedure, and modified Rankin Scale scores for all patients were ≤1.

CONCLUSIONS

Transvenous embolization of brain AVMs is feasible and may improve cure rates. The safety and long-term effects need further validation.

Assessment of periprocedural hemodynamic changes in arteriovenous malformation vessels by endovascular dual-sensor guidewire

Endovascular embolization is an important modality in the treatment of brain AVMs. Nowadays staged embolization is the method of choice for the prevention of perioperative hemorrhagic complications. Current theory suggests that simultaneous occlusion of more than 60% of AVM volume induces significant redistribution local blood flow. That, in turn, may lead to hemorrhage due to AVM rupture. Aside from angiographic findings, there is still no method that predicts the degree of safe partial embolization. Intraluminal measurement of flow velocity and pressure in the vicinity of the AVM nidus might allow detecting the changes in local hemodynamics. That can provide a valuable data and shed the light on the origin of vascular catastrophes. Ten patients underwent 12 embolization sessions with intraluminal flow velocity and pressure monitoring. The measurements were performed by dual-sensor guidewire. The "Combomap" (Volcano) system with Combowire microguidewires was chosen for measurements, as there is a documented experience of safe use of said guidewires in the cerebral vasculature. The findings observed during the study matched empirical data as well as the current physiological hypothesis of AVM hemorrhage. In conjunction with DSA runs, intraluminal flow velocity and pressure monitoring has the potential to become a valuable tool in AVM treatment.

Endogenous hormone 2-methoxyestradiol suppresses venous hypertension-induced angiogenesis through up- and down-regulating p53 and id-1

Brain arteriovenous malformations (AVMs) which associate with angiogenesis due to local hypertension, chronic cerebral ischaemia and tissue hypoxia usually lead to haemorrhage, however, the therapeutic medicine for the disease is still lacking. 2‐methoxyestradiol (2‐ME) has been shown effective in the anti‐angiogenic treatment. This study was conducted to examine whether and how 2‐ME could improve the vascular malformations. Intracranial venous hypertension (VH) model produced in adult male Sprague‐Dawley rats and culture of human umbilical vein endothelial cells (HUVECs) at the anoxia condition were used to induce in vivo and in vitro angiogenesis, respectively. Lentiviral vectors of ID‐1 and p53 genes and of their siRNA were intracranially injected into rats and transfected into HUVECs to overexpress and down‐regulate these molecules. 2‐ME treatment not only reduced the in vivo progression of brain tissue angiogenesis in the intracranial VH rats and the in vitro increases in microvasculature formation, cellular migration and HIF‐1α expression induced by anoxia in HUVECs but also reversed the up‐regulation of ID‐1 and down‐regulation of p53 in both the in vivo and in vitro angiogenesis models. All of the anti‐angiogenesis effects of 2‐ME observed in VH rats and anoxic HUVECs were abrogated by ID‐1 overexpression and p53 knockdown. Our data collectively suggest that 2‐ME treatment inhibits hypoxia/anoxia‐induced angiogenesis dependently on ID‐1 down‐regulation and p53 up‐regulation, providing a potential alternative medical treatment for un‐ruptured AVM patients.

Critical review of brain AVM surgery, surgical results and natural history in 2017

BACKGROUND

An understanding of the present standing of surgery, surgical results and the role in altering the future morbidity and mortality of untreated brain arteriovenous malformations (bAVMs) is appropriate considering the myriad alternative management pathways (including radiosurgery, embolization or some combination of treatments), varying risks and selection biases that have contributed to confusion regarding management. The purpose of this review is to clarify the link between the incidence of adverse outcomes that are reported from a management pathway of either surgery or no intervention with the projected risks of surgery or no intervention.

METHODS

A critical review of the literature was performed on the outcomes of surgery and non-intervention for bAVM. An analysis of the biases and how these may have influenced the outcomes was included to attempt to identify reasonable estimates of risks.

RESULTS

In the absence of treatment, the cumulative risk of future hemorrhage is approximately 16% and 29% at 10 and 20 years after diagnosis of bAVM without hemorrhage and 35% and 45% at 10 and 20 years when presenting with hemorrhage (annualized, this risk would be approximately 1.8% for unruptured bAVMs and 4.7% for 8 years for bAVMs presenting with hemorrhage followed by the unruptured bAVM rate). The cumulative outcome of these hemorrhages depends upon whether the patient remains untreated and is allowed to have a further hemorrhage or is treated at this time. Overall, approximately 42% will develop a new permanent neurological deficit or death from a hemorrhagic event. The presence of an associated proximal intracranial aneurysm (APIA) and restriction of venous outflow may increase the risk for subsequent hemorrhage. Other risks for increased risk of hemorrhage (age, pregnancy, female) were examined, and their purported association with hemorrhage is difficult to support. Both the Spetzler-Martin grading system (and its compaction into the Spetzler-Ponce tiers) and Lawton-Young supplementary grading system are excellent in predicting the risk of surgery. The 8-year risk of unfavorable outcome from surgery (complication leading to a permanent new neurological deficit with a modified Rankin Scale score of greater than one, residual bAVM or recurrence) is dependent on bAVM size, the presence of deep venous drainage (DVD) and location in critical brain (eloquent location). For patients with bAVMs who have neither a DVD nor eloquent location, the 8-year risk for an unfavorable outcome increases with size (increasing from 1 cm to 6 cm) from 1% to 9%. For patients with bAVM who have either a DVD or eloquent location (but not both), the 8-year risk for an unfavorable outcome increases with the size (increasing from 1 cm to 6 cm) from 4% to 35%. For patients with bAVM who have both a DVD and eloquent location, the 8-year risk for unfavorable outcome increases with size (increasing from 1 cm to 3 cm) from 12% to 38%.

CONCLUSION

Patients with a Spetzler-Ponce A bAVM expecting a good quality of life for the next 8 years are likely to do better with surgery in expert centers than remaining untreated. Ongoing research is urgently required on the outcome of management pathways for bAVM.

The natural history of cerebral arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are composed of a complex tangle of abnormal arteries and veins and are a significant source of cerebral hemorrhage and consequent morbidity and mortality in young adults, representing a diagnostic and therapeutic challenge. Current natural-history studies of cerebral AVMs report overall annual rates of 1% and 3% for the risk of epilepsy and hemorrhage, respectively. Unruptured AVMs have an annual hemorrhage rate of 2.2% while ruptured lesions have an annual hemorrhage rate of 4.5%. These hemorrhage rates are can change over time, particularly for hemorrhagic lesions, with the rebleed rate ranging from 6% to 15.8% in the first year after rupture across several studies. Besides hemorrhage, other significant risk factors for AVM hemorrhage include deep location, deep venous drainage, associated aneurysms, and pregnancy. Other factors include patient age, sex, and small AVM size, which are not currently considered significant risk factors for AVM hemorrhage. In addition to hemorrhage risk and seizure risk, the natural history of an AVM also encompasses the daily psychologic burden that a patient must endure knowing that he or she possesses an untreated AVM. This chapter reviews the epidemiology, clinical features, and natural history of cerebral AVMs.

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.

Multimodal Flow-Assisted Resection of Brain AVMs

OBJECT

The authors report their personal experience with brain arterio-venous malformations (bAVMs) surgery with a multimodal flow-assisted approach.

METHODS

Data from patients who consecutively underwent bAVM resection with the assistance of indocyanine green video-angiography (ICG-VA), micro-flow probe flowmetry, and temporary arterial clipping test under intra-operative monitoring, were retrospectively analyzed.

RESULTS

Twenty seven patients were enrolled in the study. Re-operation for residual nidus was needed in one case (3 %). Average mRS change 1 month after surgery was +0.02. In our experience, the multimodal flow-assisted approach enabled surgeons to shift from one technique to another, according to the stage of resection, AVM location, or specific issues to be addressed. Before resection, the value of ICG-VA and flowmetry in showing AVM angio-architecture and guiding surgical strategy was related to AVM features. The temporary arterial clipping-test presented a 100 % sensitivity to differentiate between an AVM feeder and a transit artery to the sensi-motor area. At the final stage of resection, flowmetry was more effective than ICG-VA in detecting residual nidus missed at dissection.

CONCLUSIONS

Multimodal flow-assisted approach in AVM surgery proved a feasible, safe, and reliable methodology to achieve AVM resection with high radicality and low morbidity rate.

Microsurgical Outcome of Cerebellar Arteriovenous Malformations: Single-Center Experience

OBJECTIVE

We aimed to describe our single-center experience in treating cerebellar arteriovenous malformations (AVMs) with microsurgical resection.

METHODS

During a 16-year period, 181 patients with cerebellar AVMs were surgically treated at the Department of Neurosurgery in Beijing Tiantan Hospital. Patient functional status was evaluated using modified Rankin Scale (mRS) scores both before treatment and at the last follow-up. The mRS scores at the last follow-up were dichotomized as good outcome (mRS <3) and poor outcome (mRS ≥3). The treatment modalities, post-treatment complications, obliteration rate, and follow-up outcomes were analyzed.

RESULTS

Of the 181 patients, 172 (95%) patients presented with initial hemorrhage and 62 (34%) patients experienced rehemorrhage before microsurgical treatment. Complete obliteration of the AVMs was achieved in 177 (97.8%) patients. Good functional outcome was achieved in 144 (80%) of the patients. The surgical mortality rate was 4.4% (8/181), and overall mortality rate was 6.6% (12/181). Poor outcome was significantly associated with increasing age (P = 0.035; odds ratio [OR], 1.030; 95% CI 1.002-1.060), presurgical mRS ≥3 (P = 0.029; OR, 2.563; 95% CI 1.101-5.968), eloquent AVM location (P = 0.015; OR, 3.058; 95% CI 1.244-7.516), and presurgical rehemorrhage (P = 0.008; OR, 3.266; 95% CI 1.358-7.858).

CONCLUSION

Good outcome can be achieved by microsurgical resection in most patients with cerebellar AVMs. Increasing age at surgery, poor presurgical functional status, eloquent AVM location, and presurgical rehemorrhage are independent predictors of poor outcomes after AVM resection. We recommend early surgical resection for all surgically accessible cerebellar AVMs to prevent subsequent hemorrhage and resultant poor neurologic outcomes.

Angioarchitecture Predicting Hemorrhage in Cerebral Arteriovenous Malformations

To find out lesions responsible for hemorrhage in arteriovenous malformations (AVMs), a retrospective study of angioarchitecture around the nidus was conducted in 27 patients who underwent conservative treatment. Comparison of angiograms revealed disappearance of an intranidal aneurysmal dilatation after the hemorrhagic events in two cases. The hematomas were adjacent to the dilatation, and no subarachnoid hemorrhage was evident. Obstruction of venous drainage, noticed in a case of spontaneous regression of AVM, was not demonstrated in the cases of hemorrhage.

The intranidal aneurysmal dilatation is likely to have caused the hemorrhage in our cases. Careful endavascular embolization using proper materials should be indicated for an intranidal aneurysmal dilatation to prevent subsequent hemorrhage.

Cerebellar Arteriovenous Malformations: Clinical Feature, Risk of Hemorrhage and Predictors of Posthemorrhage Outcome

OBJECTIVE

We aimed to summarize the clinical presentation, risk of hemorrhage, and predictors of posthemorrhage outcome in patients with cerebellar arteriovenous malformations (AVMs).

METHODS

We searched our AVM database at Beijing Tiantan Hospital and identified 225 patients with cerebellar AVMs between the year 2000 and 2015. The clinical presentation and hemorrhage risk were analyzed in all patients. Further analysis of predictors for immediate posthemorrhage outcome was performed in patients with ruptured AVMs. Posthemorrhage modified Rankin Scale (mRS) scores were dichotomized into nonsevere outcome (mRS ≤3) and severe outcome (mRS >3). Univariate and multivariate logistic regression analyses were applied to test the risk factors of hemorrhage and predictors of severe outcome.

RESULTS

Of the 225 patients, 197 (88%) presented with hemorrhage. Patients with initial hemorrhage were much younger than those with unruptured AVMs (univariate: P = 0.003; multivariate: P = 0.002). Single arterial supply (odds ratio [OR], 2.846; 95% confidence interval [CI], 1.022-7.922) and exclusively deep venous drainage (OR, 3.361; 95% CI, 1.045-10.813) were the other 2 independent risk factors for hemorrhagic presentation. Regarding the neurologic outcome immediately after hemorrhagic presentation, we used 3 models of multivariate logistic regression. Severe neurologic outcome (mRS >3) was associated with eloquent or deep AVM location, associated aneurysm, and the presence of intraventricular hemorrhage (all P < 0.05).

CONCLUSION

Cerebellar AVMs have an aggressive nature of hemorrhage. Younger age, single feeding artery, and exclusively deep venous drainage were independent risk factors for hemorrhagic presentation. Eloquent location, associated aneurysm, and presence of intraventricular hemorrhage may predict severe immediate posthemorrhage outcome.

Endovascular treatment of arteriovenous malformations

Cerebral arteriovenous malformations (AVM) are tangles of blood vessels that permit shunting of blood from the arterial to venous phase without intervening capillaries. The malformation's arterialization of a low-pressure system creates a risk of rupture that is substantially higher when associated with an aneurysm. The annual hemorrhage rate is 2.2% per year as reported in the randomized trial of unruptured brain AVMs (ARUBA; rupture risk is increased after the first event. Ruptured AVMs have a 10% mortality rate and 20%-30% morbidity rate. The treatment of choice for AVMs is microvascular resection with or without preoperative embolization. Surgical risk can be stratified based on the Spetzler-Martin grading system. Liquid embolic material and coils may be used for the treatment of AVM associated aneurysms, especially in the setting of acute rupture as a bridge to delayed surgical resection. There is some limited reported success in total endovascular treatment of AVMs, but this is not considered standard therapy at this time. Stereotactic radiosurgery (SRS) has been recently described but mainly limited to AMVs deemed too risky to approach in an open fashion and limited to 2.5cm-3cm in size. The delayed protection from hemorrhage (approximately 2-3 years) and high marginal failure/recurrence rate are the greatest concerns.

Vascular Integrity in the Pathogenesis of Brain Arteriovenous Malformation

Brain arteriovenous malformation (bAVM) is an important cause of intracranial hemorrhage (ICH), particularly in the young population. ICH is the first clinical symptom in about 50 % of bAVM patients. The vessels in bAVM are fragile and prone to rupture, causing bleeding into the brain. About 30 % of unruptured and non-hemorrhagic bAVMs demonstrate microscopic evidence of hemosiderin in the vascular wall. In bAVM mouse models, vascular mural cell coverage is reduced in the AVM lesion, accompanied by vascular leakage and microhemorrhage. In this review, we discuss possible signaling pathways involved in abnormal vascular development in bAVM.

Therapeutic management of cerebral arteriovenous malformations: a review

The therapeutic management of cerebral arteriovenous malformations has undergone significant change over the past 40 years. Embolization, radiosurgery, advanced imaging modalities, neuropsychological testing and advances in surgical technique has both significantly improved our ability to treat patients, as well as confounding the landscape as to what constitutes best medical practice. Variability in natural history provides additional challenges in that it is challenging to determine an accurate estimate of the risk of hemorrhage, morbidity and mortality. It is clear that the complexity of the treatment of these lesions demands a multidisciplinary approach. The need for a team of neurosurgeons, interventional and diagnostic neuroradiologists, neurologists, radiation oncologists and neuropsychologists will improve outcomes and aid in determining best therapy for patients.

Developmental Venous Anomaly With Asymmetrical Basal Ganglia Calcification: Two Case Reports and Review of the Literature

Developmental venous anomaly (DVA) is a common lesion formerly known as venous angioma. DVAs drain normal brain parenchyma; however, parenchymal abnormalities surrounding DVAs have been reported. Unilateral putamen and caudate calcification in the drainage territory of DVAs has so far been reported in 7 cases, all with deep venous drainage. We present two additional cases of DVAs, one with superficial and the other one with deep venous drainage, associated with basal ganglia calcifications. We emphasize that DVAs should be in the differential diagnosis of unilateral basal ganglia calcifications.

Periventricular Location as a Risk Factor for Hemorrhage and Severe Clinical Presentation in Pediatric Patients with Untreated Brain Arteriovenous Malformations

BACKGROUND AND PURPOSE

The morphologic features of brain arteriovenous malformations differ between children and adults; therefore, our aim was to analyze various features of brain arteriovenous malformations to assess the risk of hemorrhage in children.

MATERIALS AND METHODS

We identified all consecutive children admitted to Beijing Tiantan Hospital for brain arteriovenous malformations between July 2009 and April 2014. The effects of demographic characteristics and brain arteriovenous malformation morphology on hemorrhage presentation, annual bleeding rates, postnatal hemorrhage, and immediate posthemorrhagic neurologic outcomes were studied by using univariate and multivariable regression analyses.

RESULTS

A total of 108 pediatric brain arteriovenous malformation cases were identified, 66 (61.1%) of which presented with hemorrhage. Of these, 69.7% of ruptured brain arteriovenous malformations were in a periventricular location. Periventricular nidus location (OR, 3.443; 95% CI, 1.328-8.926; P = .011) and nidus size (OR, 0.965; 95% CI, 0.941-0.989; P = .005) were independent predictors of hemorrhagic presentation. The annual hemorrhage rates in children with periventricular brain arteriovenous malformations were higher at 6.88% (OR, 1.965; 95% CI, 1.155-3.341; P < .05). The hemorrhage-free survival rates were also lower for children with periventricular brain arteriovenous malformations (log-rank, P = .01). Periventricular location (hazard ratio, 1.917; 95% CI, 1.131-3.250; P = .016) and nidus size (hazard ratio, 0.983; 95% CI, 0.969-0.997; P = .015) were associated with hemorrhage after birth in pediatric brain arteriovenous malformations. An ordinal analysis showed lower immediate posthemorrhage mRS in patients with periventricular brain arteriovenous malformations (OR for greater disability, 2.71; 95% CI, 1.03-7.11; P = .043).

CONCLUSIONS

Small periventricular brain arteriovenous malformations were associated with increased hemorrhage risk in pediatric patients. Cautious follow-up of children with untreated periventricular brain arteriovenous malformations is recommended because of a higher hemorrhage risk and potentially more severe neurologic outcomes.

Association between Venous Angioarchitectural Features of Sporadic Brain Arteriovenous Malformations and Intracranial Hemorrhage

BACKGROUND AND PURPOSE

Intracranial hemorrhage is the most serious outcome for brain arteriovenous malformations. This study examines associations between venous characteristics of these lesions and intracranial hemorrhage.

MATERIALS AND METHODS

Statistical analysis was performed on a prospectively maintained data base of brain AVMs evaluated at an academic medical center. DSA, CT, and MR imaging studies were evaluated to classify lesion side, drainage pattern, venous stenosis, number of draining veins, venous ectasia, and venous reflux. Logistic regression analyses were performed to identify the association of these angiographic features with intracranial hemorrhage of any age at initial presentation.

RESULTS

Exclusively deep drainage (OR, 3.42; 95% CI, 1.87-6.26; P < .001) and a single draining vein (OR, 1.98; 95% CI, 1.26-3.08; P = .002) were associated with hemorrhage, whereas venous ectasia (OR, 0.52; 95% CI, 0.34-0.78; P = .002) was inversely associated with hemorrhage.

CONCLUSIONS

Analysis of venous characteristics of brain AVMs may help determine their prognosis and thereby identify lesions most appropriate for treatment.

Intraoperative Flow Measurement by Microflow Probe During Surgery for Brain Arteriovenous Malformations

BACKGROUND

Intraoperative quantitative flow measurement by a microvascular ultrasonic flow probe is an established methodology in aneurysm surgery.

OBJECTIVE

To test the present flow measurement procedure in brain arteriovenous malformation (AVM) surgery.

METHODS

Data from 25 patients with brain AVMs who consecutively underwent microsurgical resection with the assistance of flow measurement by a microflow probe were retrospectively analyzed. Flowmetry was performed on arterial feeders, potentially transit arteries, and venous drainage of AVM in different phases of resection.

RESULTS

A quantitative flow measurement was performed 203 times on 92 vessels. Flowmetry was able to define the flow direction of AVM vessels in all cases, thereby discriminating between arterial feeders and venous drainages, both superficially and deeply located. During AVM dissection, flowmetry identified a transit artery in 12% of cases by detecting a flow drop between 2 points of the same vessel. At the final stage of resection, a residual nidus, potentially missed at surgical dissection, was detected when the flow value of venous drainage was greater than 4 mL/min (20% of patients). Pre-resection microflow probe measurements were concordant with indocyanine green videoangiography data on AVM angioarchitecture in all cases. No microflow probe–induced AVM vessel injury was reported. Complete AVM resection was achieved in all cases with a low morbidity (modified Rankin Scale score ⩽1).

CONCLUSION

Multistage intraoperative quantitative flow measurement proved to be a feasible, safe, repeatable, and reliable methodology to assist surgery in different phases of AVM resection. Further studies are needed to assess the impact of this approach on AVM patient outcomes.

Number and location of draining veins in pediatric arteriovenous malformations: association with hemorrhage

OBJECT

The significance of draining vein anatomy is poorly defined in pediatric arteriovenous malformations (AVMs). In adult cohorts, the presence of fewer veins has been shown to lead to an increased rate of hemorrhage, but this phenomenon has not yet been studied in pediatric AVMs. This report analyzes the impact of draining vein anatomy on presentation and outcome in a large series of pediatric AVMs.

METHODS

Eighty-five pediatric patients with AVMs were treated at the Columbia University Medical Center between 1991 and 2012. Charts were retrospectively reviewed for patient characteristics, clinical course, neurological outcome, and AVM angioarchitectural features identified on the angiogram performed at presentation. Univariate analyses were performed using chi-square test and ANOVA when appropriate; multivariate analysis was performed using logistic regression.

RESULTS

Four patients were excluded due to incomplete records. Twenty-seven patients had 2 or 3 draining veins; 12 (44.4%) of these patients suffered from hemorrhage prior to surgery. Fifty-four patients had 1 draining vein; 39 (72.2%) of these 54 suffered from hemorrhage. Independent predictors of hemorrhage included the presence of a single draining vein (p = 0.04) and deep venous drainage (p = 0.02). Good outcome (modified Rankin Scale [mRS] score < 3) on discharge was found to be associated with higher admission Glasgow Coma Scale (GCS) scores (p = 0.0001, OR 0.638, 95% CI 0.40-0.93). Poor outcome (mRS score > 2) on discharge was found to be associated with deep venous drainage (p = 0.04, OR 4.68, 95% CI 1.1-19.98). A higher admission GCS score was associated with a lower discharge mRS score (p = 0.0003, OR 0.6, 95% CI 0.46-0.79), and the presence of a single draining vein was associated with a lower mRS score on long-term follow-up (p = 0.04, OR 0.18, 95% CI 0.032-0.99).

CONCLUSIONS

The authors' data suggest that the presence of a single draining vein or deep venous drainage plays a role in hemorrhage risk and ultimate outcome in pediatric AVMs. Small AVMs with a single or deep draining vein may have the highest risk of hemorrhage.

Stereotactic radiosurgery for arteriovenous malformations of the cerebellum

Object

Arteriovenous malformations (AVMs) of the posterior fossa have an aggressive natural history and propensity for hemorrhage. Although the cerebellum accounts for the majority of the posterior fossa volume, there is a paucity of stereotactic radiosurgery (SRS) outcome data for AVMs of this region. The authors sought to evaluate the long-term outcomes and risks of cerebellar AVM radiosurgery.

Methods

This single-institution retrospective analysis reviewed the authors' experience with Gamma Knife surgery during the period 1987–2007. During this time 64 patients (median age 47 years, range 8–75 years) underwent SRS for a cerebellar AVM. Forty-seven patients (73%) presented with an intracranial hemorrhage. The median target volume was 3.85 cm3 (range 0.2–12.5 cm3), and the median marginal dose was 21 Gy (range 15–25 Gy).

Results

Arteriovenous malformation obliteration was confirmed by MRI or angiography in 40 patients at a median follow-up of 73 months (range 4–255 months). The actuarial rates of total obliteration were 53% at 3 years, 69% at 4 years, and 76% at 5 and 10 years. Elevated obliteration rates were statistically higher in patients who underwent AVM SRS without prior embolization (p = 0.005). A smaller AVM volume was also associated with a higher rate of obliteration (p = 0.03). Four patients (6%) sustained a hemorrhage during the latency period and 3 died. The cumulative rates of AVM hemorrhage after SRS were 6% at 1, 5, and 10 years. This correlated with an overall annual hemorrhage rate of 2.0% during the latency interval. One patient experienced a hemorrhage 9 years after confirmed MRI and angiographic obliteration. A permanent neurological deficit due to adverse radiation effects developed in 1 patient (1.6%) and temporary complications were seen in 2 additional patients (3.1%).

Conclusions

Stereotactic radiosurgery proved to be most effective for patients with smaller and previously nonembolized cerebellar malformations. Hemorrhage during the latency period occurred at a rate of 2.0% per year until obliteration occurred.

Advances in Radiosurgery for Arteriovenous Malformations of the Brain

Arteriovenous malformations of the brain are a considerable source of morbidity and mortality for patients who harbor them. Although our understanding of this disease has improved, it remains in evolution. Advances in our ability to treat these malformations and the modes by which we address them have also improved substantially. However, the variety of patient clinical and disease scenarios often leads us into challenging and complex management algorithms as we balance the risks of treatment against the natural history of the disease. The goal of this article is to provide a focused review of the natural history of cerebral arteriovenous malformations, to examine the role of stereotactic radiosurgery, to discuss the role of endovascular therapy as it relates to stereotactic radiosurgery, and to look toward future advances.

Notch1 and 4 signaling responds to an increasing vascular wall shear stress in a rat model of arteriovenous malformations

Notch signaling is suggested to promote the development and maintenance of cerebral arteriovenous malformations (AVMs), and an increasing wall shear stress (WSS) contributes to AVM rupture. Little is known about whether WSS impacts Notch signaling, which is important for understanding the angiogenesis of AVMs. WSS was measured in arteriovenous fistulas (AVF) surgically created in 96 rats at different time points over a period of 84 days. The expression of Notch receptors 1 and 4 and their ligands, Delta1 and 4, Jagged1, and Notch downstream gene target Hes1 was quantified in “nidus” vessels. The interaction events between Notch receptors and their ligands were quantified using proximity ligation assay. There was a positive correlation between WSS and time (r = 0.97; P < 0.001). The expression of Notch receptors and their ligands was upregulated following AVF formation. There was a positive correlation between time and the number of interactions between Notch receptors and their ligands aftre AVF formation (r = 0.62, P < 0.05) and a positive correlation between WSS and the number of interactions between Notch receptors and their ligands (r = 0.87, P < 0.005). In conclusion, an increasing WSS may contribute to the angiogenesis of AVMs by activation of Notch signaling.