A 3-tier classification of cerebral arteriovenous malformations

Optimal Timing of Microsurgical Treatment for Ruptured Arteriovenous Malformations: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

The timing of microsurgical treatment (MST) for ruptured brain arteriovenous malformations (bAVM) is a contentious issue in the literature. This study aimed to investigate the impact of MST timing on outcomes in patients with ruptured bAVMs, considering MST with and without preoperative endovascular treatment (EVT).

METHOD

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, a comprehensive search was conducted across multiple databases, yielding 15 studies meeting the inclusion criteria. The timing was defined as the duration from the rupture of bAVM to the MST. The patients were divided into 4 different groups based on MST timing: <48 hours, <1 week, <2 weeks, and <1 month. The primary outcome was favorable outcome defined as a modified Rankin Scale score of 0 to 2 or a Glasgow Outcome Scale score of 4 to 5 in the last clinical follow-up. Secondary outcomes included periprocedural mortality and complete excision.

RESULTS

MST time >48 hours were associated with a significantly higher favorable outcome rate (odds ratio: 9.71, 95% Cl: 3.09-30.57, P < .01) and a lower mortality rate (OR: 0.15, 95% Cl: 0.02-0.88, P = .04) compared with MST timing ≤48 hours. After exclusion of patients who underwent MST with preoperative EVT, MST time >48 hours had a significantly higher rate of favorable outcome (OR: 9.39, 95% CI: 2.53-34.89, P < .01).

CONCLUSION

This meta-analysis suggests that delayed surgical intervention beyond 48 hours may be associated with improved favorable outcomes in patients who underwent MST with and without preoperative EVT for ruptured bAVMs.

Untangling sporadic brain arteriovenous malformations: towards targeting the KRAS/MAPK pathway

Brain arteriovenous malformations (AVMs) are vascular lesions characterized by abnormal connections between parenchymal arteries and veins, bypassing a capillary bed, and forming a nidus. Brain AVMs are consequential as they are prone to rupture and associated with significant morbidity. They can broadly be subdivided into hereditary vs. sporadic lesions with sporadic brain AVMs representing the majority of all brain AVMs. However, little had been known about the pathogenesis of sporadic brain AVMs until the landmark discovery in 2018 that the majority of sporadic brain AVMs carry somatic activating mutations of the oncogene, Kirsten rat sarcoma viral oncogene homologue (KRAS), in their endothelial cells. Here, we review the history of brain AVMs, their treatments, and recent advances in uncovering the pathogenesis of sporadic brain AVMs. We specifically focus on the latest studies suggesting that pharmacologically targeting the KRAS/MEK pathway may be a potentially efficacious treatment for sporadic brain AVMs.

Primary Embolization of Cerebral Arteriovenous Malformations With Intention to Cure: A Systematic Review of Literature and Meta-Analysis

BACKGROUND AND OBJECTIVES

The treatment of brain arteriovenous malformations (AVMs) involves multiple approaches, including embolization, microsurgical resection, and radiosurgery. With the advent of new embolisates, dual-lumen balloon catheters, detachable tip microcatheters, and transvenous embolization, endovascular AVM obliteration has become more effective. Although adjuvant embolization and embolization are commonly used, the safety and effectiveness of curative embolization remain unclear.

METHODS

We conducted a systematic literature review using PubMed, Ovid Medline, and Web of Science to identify studies reporting outcomes in patients with AVMs who underwent primary embolization with the intention to cure. We collected data on patient characteristics, AVM features, complications, and radiographic and clinical outcomes for meta-analysis.

RESULTS

We identified 25 studies with a total of 1425 patients with 1427 AVMs who underwent curative embolization. Of these patients, 70% were low grade (pooled = 61% [39-82]), 67% were <3 cm (pooled = 78% [60-92]), and 75% were in superficial locations (pooled = 80% [72-86]). At last radiographic follow-up (mean, 16.7 ± 10.9 months), the full obliteration rate was 52% (pooled = 61% [43-77]) and retreatment rate was 25% (pooled = 17% [8.3-27]). At last clinical follow-up (mean, 24.2 ± 13.3 months), the poor clinical outcome rate was 7.9% (pooled = 4.4% [1.3-8.7]) and symptomatic complication rate was 13% (pooled = 13% [8-19]). There was no significant difference in the rate of radiographic cure, need for retreatment, and poor outcomes between ruptured and unruptured AVMs. Symptomatic complications were more common in the treatment of unruptured AVMs. The primary outcomes showed high heterogeneity (I 2 = 72%-94%).

CONCLUSION

Curative embolization of AVM is primarily reserved for small and low-grade AVMs, with highly variable outcomes. Our findings suggest poor radiographic outcomes and increased risk of complications. Outcomes are highly dependent on patient selection and technique used. Large multicenter prospective studies are required to further guide patient selection, categorize clinical and radiographic outcomes, and identify subgroup of patients that may benefit from curative embolization.

Ruptured brain arteriovenous malformation in a pregnant woman: a case report

BACKGROUND

Brain arteriovenous malformations (bAVMs) are vascular lesions that commonly present with intracranial haemorrhage. Pregnancy has been associated with an increased risk of bAVM rupture. However, their natural history in pregnant women is uncertain.

CASE DESCRIPTION

A 27-year-old female at 28 weeks of gestation presented with a compromised neurological status secondary to a ruptured left frontal Spetzler-Martin scale (SM) III + bAVM. An emergent caesarean section was performed due to the high risk of foetal distress. Endovascular treatment successfully controlled the bleeding site, and stereotactic radiosurgery was offered as a subsequent treatment option.

CONCLUSION

bAVMs should be considered in pregnant women with intracranial haemorrhage. The management of these lesions during pregnancy is controversial. Surgical risk and foetal development should be considered when selecting a management strategy.

Diagnostic and therapeutic dilemmas of asymptomatic intracranial AVMs: A case report and evidence-based review

First described by Virchow in the 19th century, intracranial arteriovenous malformations (AVMs) are complex, tangle-shaped vascular lesions with a number of associated neuroparenchymal, hemodynamic, and angio-architectural changes. However, the clinical description of extracranial AVMs dates back to the Ebers Papyrus (c. 1500 BC), with a still unknown definitive underlying etiology thus far. AVMs are rare lesions, with approximately 0.15% incidence and 0.001-0.5% prevalence, but of high importance as they tend to affect young patients who are frequently otherwise healthy. In the majority of cases, AVMs present as sudden intracranial hemorrhages that require immediate intervention, but incidentally-detected unruptured AVMs are only found in ∼15% of cases, leaving a confusing dilemma regarding the appropriate next step, particularly given the several therapeutic interventions available and clinical trials that were vulnerable to follow-up criticism. Herein, we present a case of an incidentally detected asymptomatic AVM in a 15-year-old boy via advanced imaging techniques that was initially misinterpreted as a post-traumatic subarachnoid hemorrhage on routine imaging studies. In providing a comprehensive overview of pathological classification schemes and the currently available diagnostic options for these silent dilemmatic AVMs, we highlight three management techniques: microsurgical resection, endovascular embolization, and stereotactic surgery, with the best option depends mostly on addressing lesion resection properly with minimal associated mortality and morbidity.

Intracranial Vascular Malformations in Children

Intracranial vascular malformations (IVMs) represent a significant challenge in pediatric medicine due to their diagnostic and therapeutic complexity. Despite their rarity, the severity of potential neurologic outcomes necessitates a comprehensive understanding and approach to management. This article aims to provide an overview of pediatric IVMs, specifically nidal arteriovenous malformations, cavernous malformations, capillary telangiectasias, and developmental venous anomalies, and highlight the importance of advanced diagnostic imaging and therapeutic strategies in improving outcomes. Vein of Galen malformations, pial arteriovenous fistulas, dural sinus malformations, and intracranial venous malformations will be addressed in other articles. Following a discussion of imaging and clinical considerations within the field, novel imaging techniques will be discussed.

Endovascular Treatment of Brain Arteriovenous Malformations in Pediatric Patients: A Single Center Experience and Review of the Literature

BACKGROUND

 Brain arteriovenous malformations (bAVMs) are abnormal vascular connections with direct arteriovenous shunts, generally symptomatic in the adult life. However, a small number of bAVMs may manifest in pediatric patients, with higher bleeding risk and mortality rates when compared to adults. The purpose of this study is to review our experience with endovascular treatment of bAVMs in pediatric patients.

METHODS

 This is a retrospective analysis of all bAVMs in pediatric patients (0-18 years) who underwent diagnostic digital subtraction angiography (DSA) at our institution from January 2010 to June 2021.

RESULTS

 Twenty-six patients met the inclusion criteria, of which 12 underwent endovascular treatment. Treated patients had a mean age of 10.25 years and 58% were females. Complete angiographic exclusion was achieved in five (42%) patients with endovascular treatment. Five patients with residual bAVM after embolization needed adjuvant therapy with surgery (n = 3) or stereotactic radiosurgery (SRS; n = 2). Two patients are still undergoing embolization sessions. Procedure-related complications occurred in two patients (17%) and included small vessel perforation and an occipital ischemic stroke. Two patients showed bAVM recurrence on follow-up (17%) and subsequently underwent SRS (n = 1) or surgery (n = 1), both resulting in complete bAVM exclusion. All patients had a modified Rankin scale (mRS) score of 0 to 2 on follow-up.

CONCLUSION

 Our experience supports the effectiveness and safety of endovascular treatment of bAVM in selected pediatric patients. A multidisciplinary approach combining surgery and SRS is warranted to achieve higher complete bAVM obliteration rates. Long-term follow-up is important as these lesions may show recurrence over time, especially in the pediatric population.

Association of the combined stereotactic radiosurgery and embolization strategy and long-term outcomes in brain arteriovenous malformations with a volume ≤10 mL: a nationwide multicenter observational prospective cohort study

BACKGROUND

To compare the long-term outcomes of stereotactic radiosurgery (SRS) with or without prior embolization in brain arteriovenous malformations (AVMs) (volume ≤10 mL) for which SRS is indicated.

METHODS

Patients were recruited from a nationwide multicenter prospective collaboration registry (the MATCH study) between August 2011 and August 2021, and categorized into combined embolization and SRS (E+SRS) and SRS alone cohorts. We performed propensity score-matched survival analysis to compare the long-term risk of non-fatal hemorrhagic stroke and death (primary outcomes). The long-term obliteration rate, favorable neurological outcomes, seizure, worsened mRS score, radiation-induced changes, and embolization complications were also evaluated (secondary outcomes). Hazard ratios (HRs) were calculated using Cox proportional hazards models.

RESULTS

After study exclusions and propensity score matching, 486 patients (243 pairs) were included. The median (IQR) follow-up duration for the primary outcomes was 5.7 (3.1-8.2) years. Overall, E+SRS and SRS alone were similar in preventing long-term non-fatal hemorrhagic stroke and death (0.68 vs 0.45 per 100 patient-years; HR=1.46 (95% CI 0.56 to 3.84)), as well as in facilitating AVM obliteration (10.02 vs 9.48 per 100 patient-years; HR=1.10 (95% CI 0.87 to 1.38)). However, the E+SRS strategy was significantly inferior to the SRS alone strategy in terms of neurological deterioration (worsened mRS score: 16.0% vs 9.1%; HR=2.00 (95% CI 1.18 to 3.38)).

CONCLUSIONS

In this observational prospective cohort study, the combined strategy of E+SRS does not show substantial advantages over SRS alone. The findings do not support pre-SRS embolization for AVMs with a volume ≤10 mL.

A comprehensive analysis of patients with cerebral arteriovenous malformation with headache: assessment of risk factors and treatment effectiveness

BACKGROUND

Due to the high mortality and disability rate of intracranial hemorrhage, headache is not the main focus of research on cerebral arteriovenous malformation (AVM), so research on headaches in AVM is still scarce, and the clinical understanding is shallow. This study aims to delineate the risk factors associated with headaches in AVM and to compare the effectiveness of various intervention treatments versus conservative treatment in alleviating headache symptoms.

METHODS

This study conducted a retrospective analysis of AVMs who were treated in our institution from August 2011 to December 2021. Multivariable logistic regression analysis was employed to assess the risk factors for headaches in AVMs with unruptured, non-epileptic. Additionally, the effectiveness of different intervention treatments compared to conservative management in alleviating headaches was evaluated through propensity score matching (PSM).

RESULTS

A total of 946 patients were included in the analysis of risk factors for headaches. Multivariate logistic regression analysis identified that female (OR 1.532, 95% CI 1.173-2.001, p = 0.002), supply artery dilatation (OR 1.423, 95% CI 1.082-1.872, p = 0.012), and occipital lobe (OR 1.785, 95% CI 1.307-2.439, p < 0.001) as independent risk factors for the occurrence of headaches. There were 443 AVMs with headache symptoms. After propensity score matching, the microsurgery group (OR 7.27, 95% CI 2.82-18.7 p < 0.001), stereotactic radiosurgery group(OR 9.46, 95% CI 2.26-39.6, p = 0.002), and multimodality treatment group (OR 8.34 95% CI 2.87-24.3, p < 0.001) demonstrate significant headache relief compared to the conservative group. However, there was no significant difference between the embolization group (OR 2.24 95% CI 0.88-5.69, p = 0.091) and the conservative group.

CONCLUSIONS

This study identified potential risk factors for headaches in AVMs and found that microsurgery, stereotactic radiosurgery, and multimodal therapy had significant benefits in headache relief compared to conservative treatment. These findings provide important guidance for clinicians when developing treatment options that can help improve overall treatment outcomes and quality of life for patients.

Most Promising Approaches to Improve Brain AVM Management: ARISE I Consensus Recommendations

Brain arteriovenous malformations (bAVMs) are complex, and rare arteriovenous shunts that present with a wide range of signs and symptoms, with intracerebral hemorrhage being the most severe. Despite prior societal position statements, there is no consensus on the management of these lesions. ARISE (Aneurysm/bAVM/cSDH Roundtable Discussion With Industry and Stroke Experts) was convened to discuss evidence-based approaches and enhance our understanding of these complex lesions. ARISE identified the need to develop scales to predict the risk of rupture of bAVMs, and the use of common data elements to perform prospective registries and clinical studies. Additionally, the group underscored the need for comprehensive patient management with specialized centers with expertise in cranial and spinal microsurgery, neurological endovascular surgery, and stereotactic radiosurgery. The collection of prospective multicenter data and gross specimens was deemed essential for improving bAVM characterization, genetic evaluation, and phenotyping. Finally, bAVMs should be managed within a multidisciplinary framework, with clinical studies and research conducted collaboratively across multiple centers, harnessing the collective expertise and centralization of resources.

Current and Future Applications of Arterial Spin Labeling MRI in Cerebral Arteriovenous Malformations

Arterial spin labeling (ASL) has emerged as a promising noninvasive tool for the evaluation of both pediatric and adult arteriovenous malformations (AVMs). This paper reviews the advantages and challenges associated with the use of ASL in AVM assessment. An assessment of the diagnostic workup of AVMs and their variants in both adult and pediatric populations is proposed. Evaluation after treatments, whether endovascular or microsurgical, was similarly examined. ASL, with its endogenous tracer and favorable safety profile, offers functional assessment and arterial feeder identification. ASL has demonstrated strong performance in identifying feeder arteries and detecting arteriovenous shunting, although some studies report inferior performance compared with digital subtraction angiography (DSA) in delineating venous drainage. Challenges include uncertainties in sensitivity for specific AVM features. Detecting AVMs in challenging locations, such as the apical cranial convexity, is further complicated, demanding careful consideration due to the risk of underestimating total blood flow. Navigating these challenges, ASL provides a noninvasive avenue with undeniable merits, but a balanced approach considering its limitations is crucial. Larger-scale prospective studies are needed to comprehensively evaluate the diagnostic performance of ASL in AVM assessment.

Treatment of Brain Arteriovenous Malformations

Brain arteriovenous malformations (AVMs) are a rare entity of vascular anomalies, characteristic of anatomical shunting where arterial blood directly flows into the venous circulation. The main aim of the active treatment policy of brain AVMs is the prevention of haemorrhage. There are well-established treatment strategies that continually improve in their safety and efficacy, primarily due to the advances in imaging modalities, targeted and novel techniques, the development of alternative treatment approaches, and even better experience with the disease itself. There are interesting imaging novelties that may be prospectively applicable in the decision-making and planning of the most effective treatment approach for individual patients with intracranial AVM. Surgery is often considered the first-line treatment; however, each patient should be evaluated individually, and the risks of the active treatment policy should not overcome the benefits of the spontaneous natural history of the disease. All treatment modalities, i.e., surgery, radiosurgery, endovascular embolization, and observation, are justified but need to be meticulously selected for each individual patient in order to deliver the best treatment outcome. This chapter deals with historical and currently applied dogmas, followed by introductions of advances in each available treatment modality of AVM management.

Fractal-Based Analysis of Arteriovenous Malformations (AVMs)

Arteriovenous malformations (AVMs) are cerebrovascular lesions consisting of a pathologic tangle of the vessels characterized by a core termed the nidus, which is the "nest" where the fistulous connections occur. AVMs can cause headache, stroke, and/or seizures. Their treatment can be challenging requiring surgery, endovascular embolization, and/or radiosurgery as well. AVMs' morphology varies greatly among patients, and there is still a lack of standardization of angioarchitectural parameters, which can be used as morphometric parameters as well as potential clinical biomarkers (e.g., related to prognosis).In search of new diagnostic and prognostic neuroimaging biomarkers of AVMs, computational fractal-based models have been proposed for describing and quantifying the angioarchitecture of the nidus. In fact, the fractal dimension (FD) can be used to quantify AVMs' branching pattern. Higher FD values are related to AVMs characterized by an increased number and tortuosity of the intranidal vessels or to an increasing angioarchitectural complexity as a whole. Moreover, FD has been investigated in relation to the outcome after Gamma Knife radiosurgery, and an inverse relationship between FD and AVM obliteration was found.Taken altogether, FD is able to quantify in a single and objective value what neuroradiologists describe in qualitative and/or semiquantitative way, thus confirming FD as a reliable morphometric neuroimaging biomarker of AVMs and as a potential surrogate imaging biomarker. Moreover, computational fractal-based techniques are under investigation for the automatic segmentation and extraction of the edges of the nidus in neuroimaging, which can be relevant for surgery and/or radiosurgery planning.

Recurrence of Cerebral Arteriovenous Malformation Following Complete Obliteration Through Endovascular Embolization

Arteriovenous malformation (AVM) recurrence after embolization was rarely reported. This study aimed to explore the potential risk factors of recurrence in angiographically obliterated AVMs treated with endovascular embolization. This study reviewed AVMs treated with embolization only in a prospective multicenter registry from August 2011 to December 2021, and ultimately included 92 AVMs who had achieved angiographic obliteration. Recurrence was assessed by follow-up digital subtraction angiography (DSA) or magnetic resonance imaging (MRI). Hazard ratios (HRs) with 95% confidence intervals were calculated using Cox proportional hazards regression models. Nineteen AVMs exhibited recurrence on follow-up imaging. The recurrence rates after complete obliteration at 6 months, 1 year, and 2 years were 4.35%, 9.78%, and 13.0%, respectively. Multivariate Cox regression analysis identified diffuse nidus (HR 3.208, 95% CI 1.030-9.997, p=0.044) as an independent risk factor for recurrence. Kaplan-Meier analysis confirmed a higher cumulative risk of recurrence with diffuse nidus (log-rank, p=0.016). Further, in the exploratory analysis of the effect of embolization timing after AVM rupture on recurrence after the complete obliteration, embolization within 7 days of the hemorrhage was found as an independent risk factor (HR 4.797, 95% CI 1.379-16.689, p=0.014). Kaplan-Meier analysis confirmed that embolization within 7 days of the hemorrhage was associated with a higher cumulative risk of recurrence in ruptured AVMs (log-rank, p<0.0001). This study highlights the significance of diffuse nidus as an independent risk factor for recurrence after complete embolization of AVMs. In addition, we identified a potential recurrent risk associated with early embolization in ruptured AVMs.

Evolution of clinical and translational advances in the management of pediatric arteriovenous malformations

Arteriovenous malformations (AVMs) represent one of the most challenging diagnoses in pediatric neurosurgery. Until recently, the majority of AVMs was only identified after hemorrhage and primarily treated with surgery. However, recent advances in a wide range of fields-imaging, surgery, interventional radiology, radiation therapy, and molecular biology-have profoundly advanced the understanding and therapy of these complex lesions. Here we review the progress made in pediatric AVMs with a specific focus on innovations relevant to clinical care.

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.

Embolization of midbrain arteriovenous malformation fed by the artery of Percheron in a child, the first case report and literature review

BACKGROUND

Artery of Percheron (AOP) as main feeder artery of arteriovenous malformation (AVM) is extremely rare. Two cases of thalamic AVM fed by AOP have been reported to date and only one AVM been removed by microsurgery when attempt of intervention embolization failed. Midbrain AVM fed by AOP has not been reported yet.

CASE PRESENTATION

Here, we presented the first successful embolized case of midbrain AVM supplied by the AOP in a 10-year-old boy, who suffered dual oculomotor nerve palsy and secondary hemorrhage before embolization. During endovascular embolization, selective angiography by 1.2 Fr. Magic microcatheter showed an intranidal aneurysm located on the distal AOP. Two injections of a 1:4 ratio mixture of NBCA-MS completely occlude the nidus and intranidal aneurysm with no complications occurred. The child recovered well and the oculomotor deficits improved.

CONCLUSION

This case highlighted that AOP is a clinically significant branch associated with AVM in midbrain and thalamus. Moreover, intervention embolization of midbrain AVM fed by AOP is a considerable therapeutic strategy.

Microsurgery Versus Stereotactic Radiosurgery for Treatment of Patients With Brain Arteriovenous Malformation: A Systematic Review and Meta-Analysis

BACKGROUND

Treatment decision-making for brain arteriovenous malformations (bAVMs) with microsurgery or stereotactic radiosurgery (SRS) is controversial.

OBJECTIVE

To conduct a systematic review and meta-analysis to compare microsurgery vs SRS for bAVMs.

METHOD

Medline and PubMed were searched from inception to June 21, 2022. The primary outcomes were obliteration and follow-up hemorrhage, and secondary outcomes were permanent neurological deficit, worsened modified Rankin scale (mRS), follow-up mRS > 2, and mortality. The GRADE approach was used for grading the level of evidence.

RESULTS

Eight studies were included, which yielded 817 patients, of which 432 (52.8%) and 385 (47.1%) patients underwent microsurgery and SRS, respectively. Two cohorts were comparable in age, sex, Spetzler-Martin grade, nidus size, location, deep venous drainage, eloquence, and follow-up. In the microsurgery group, the odds ratio (OR) of obliteration was higher (OR = 18.51 [11.05, 31.01], P < .000001, evidence: high) and the hazard ratio of follow-up hemorrhage was lower (hazard ratio = 0.47 [0.23, 0.97], P = .04, evidence: moderate). The OR of permanent neurological deficit was higher with microsurgery (OR = 2.85 [1.63, 4.97], P = .0002, evidence: low), whereas the OR of worsened mRS (OR = 1.24 [0.65, 2.38], P = .52, evidence: moderate), follow-up mRS > 2 (OR = 0.78 [0.36, 1.7], P = .53, evidence: moderate), and mortality (OR = 1.17 [0.41, 3.3], P = .77, evidence: moderate) were comparable between the groups.

CONCLUSION

Microsurgery was superior at obliterating bAVMs and preventing further hemorrhage. Despite a higher rate of postoperative neurological deficit with microsurgery, functional status and mortality were comparable with patients who underwent SRS. Microsurgery should remain a first-line consideration for bAVMs, with SRS reserved for inaccessible locations, highly eloquent areas, and medically high-risk or unwilling patients.

Microsurgical Treatment of Arteriovenous Malformations: A Single-Center Study Experience

OBJECTIVE

The purpose of the study was to assess the functional outcomes after microsurgical resection of arteriovenous malformations (AVMs) and to compare the results between patients eligible for A Randomized Trial of Unruptured Brain Arteriovenous Malformations in this surgical series to the results reported and the ARUBA study.

METHODS

We reviewed the records of 169 patients who underwent microsurgical treatment of arteriovenous malformation (AVMs) in our institution between January 2016 and December 2021. These patients' functional status was assessed using modified Rankin Scale (mRS) scores at the last follow-up and before treatment. The mRS scores at the latest follow-up were classified into good outcomes (mRS < 3) and poor outcomes (mRS ≥ 3). Clinical presentation, patients' demographics, AVM characteristics, follow-up time, and obliteration rate were analyzed. Subgroup analyses were performed on the whole cohort, comparing Spetzler-Martin Grade I and Grade II, and ARUBA-eligible AVMs.

RESULTS

The initial hemorrhagic presentation occurred in 71 (42%) out of 169 patients. The majority of the patients presented with headaches (73%). The AVMs were completely obliterated in 166 (98.2%) patients. The series included 65 Spetzler-Martin Grade I (38.5%), 46 Grade II (27.2%), 32 Grade III (18.9%), 22 Grade IV (13%), and 4 Grade V (2.4%) AVMs. There were 98 unruptured and 79 ARUBA-eligible cases. Also, optimal functional outcome was achieved in 145 (85.8%) patients. The overall mortality rate was 5.3% (9/169). The multivariate analysis illustrated that a poor outcome was significantly associated with presurgical mRS ≥3 (p < 0.013; OR, 0.206; 95% CI 0.059-0.713), increasing age (p < 0.045; odds ratio [OR], 1.022; 95% CI 1.000-0.045), and female gender (p < 0.009; OR, 2.991; 95% CI 1.309-6.832).

CONCLUSIONS

Our study suggests that better outcomes can be obtained using microsurgical resection in the majority of patients with AVMs. Independent predictors of poor outcomes after surgical resection of AVMs include increasing age at the time of surgery, poor presurgical functional status, and female gender. Supposing that patients are more suitable for microsurgery after presurgical examination, outcomes are normally better in that case than those achieved by multimodal interventions (such as conservative treatment or ARUBA treatment arm). Therefore, we recommend early surgical removal on all surgically accessible AVMs to prevent successive hemorrhages and the consequences of poor neurological outcomes.

The angio-architectural features of brain arteriovenous malformations: is it possible to predict the probability of rupture?

BACKGROUND

Hemorrhage is the most devastating complication of brain arteriovenous malformations (bAVMs), and to date, there is still concern about the needing for treatment in case of unruptured and asymptomatic bAVM. In fact, the morbidity and mortality of treatments may exceed that of the AVM's natural history. None of the classifications and scores for bAVM allows to predict the risk of bleeding. In this study, we aimed to identify the angio-architectural characteristics of brain AVMs associated with bleeding.

METHODS

We retrospectively evaluated all consecutive patients diagnosed with cerebral AVMs, between January 2010 and December 2019 from our prospective bAVM database. Univariate and multivariate logistic regression analysis were used to evaluate relationships between angio-architectural features of ruptured and unruptured bAVMs.

RESULTS

Of the 143 retrieved bAVMs, 65 were unruptured and 78 were ruptured. The univariate logistic regression analysis demonstrated statistically significant differences into angio-architectural features of unruptured and ruptured bAVMs. The multivariate logistic regression analysis fitted well (p =.113) with a good discrimination capacity (ROC = 0.83) of three independent angio-architectural features mainly related to bleeding in bAVMs: a smaller diameter of the nidus (p < .001), the absence of venous drainage alterations (p = .047), of the presence of prenidal aneurysms (p = .005).

CONCLUSIONS

In our study, several features resulted related to an increased probability of rupture for bAVMs, among which the more relevant were a small diameter of the nidus, the absence of venous drainage alterations, and the presence of prenidal aneurysms.

Endovascular Management of Brain Arteriovenous Malformations

Due to the risk of cerebral hemorrhage, and its related morbidity-mortality, brain arteriovenous malformations (bAVMs) are a rare and potentially life-threatening disease. Despite this, there is only one randomized controlled trial on bAVM management, A Randomized trial of Unruptured Brain Arteriovenous malformations (ARUBA). The results of the ARUBA trial favor a noninterventional approach in the case of an unruptured bAVM; however, implementation of these findings is challenging in daily practice. Instead, management of bAVM relies on multidisciplinary discussions that lead to patient-specific strategies based on patient preferences, local expertise, and experience in referral centers. Considering the diverse patterns of presentation and numerous treatment modalities, implementing standardized guidelines in this context proves challenging, notwithstanding the recommendations or expert opinions offered. Endovascular treatment (EVT) of bAVM can be curative, or can serve as an adjunct treatment prior to surgery or radiosurgery ("pre-EVT"). EVT practice is in constant evolution (i.e., venous approach, combination with surgery during the same anesthesia, etc.). Liquid embolic agents such as ethylene vinyl alcohol (EVOH) copolymer and cyanoacrylates (CYA), and their method of injection to increase bAVM occlusion have also benefited from technical evolutions such as the use of adjunctive flow arrest techniques (mini balloons, pressure cooker technique, and multiple catheters). Further research is necessary to evaluate the advantages and disadvantages of EVT for bAVM.

Recurrence of arteriovenous malformations of the brain after complete surgical resection. Kuopio University Hospital experience and systematic review of the literature

Treatment for arteriovenous malformations of the brain (bAVMs) aims to achieve complete removal or occlusion of the lesion in order to eradicate the risk of rupture and subsequent morbidity associated with these lesions. Despite initially successful treatment, bAVMs may carry a risk of recurrence especially in younger patients. We studied the rate of recurrence of surgically treated bAVMs at Kuopio University Hospital (KUH) in 1981-2021. The study population was collected retrospectively from KUH databases and presented a cohort of 135 surgically treated bAVMs with complete occlusion of the lesion. We also performed a systematic literature review on this topic. In our series, 6 out of 135 (4.4%) patients with angiographically confirmed removal of the lesion later developed a recurrent bAVM with a median time to diagnosis of recurrence of 7.46 years. In pediatric patients, the rate was 5 out of 17 (29.4%). bAVM recurrence was associated with age (p = 0.001) and initial hemorrhagic presentation (p = 0.039). Median age of the study population was 37 years (min 0, max 70), and 51/135 (37.8%) of the patients were female. Seventeen (12.6%) of the 135 bAVM patients were considered pediatric (18 years old or younger) at the time of the operation. In the literature review, 79 of 1739 (4.5%) of surgically treated patients later developed a recurrence with a mean delay of 3.1 years until diagnosis of recurrence. Young surgically treated bAVM patients with a hemorrhagic presentation at initial diagnosis are at a relatively high risk of bAVM recurrence. Follow-up imaging should be arranged for these patients in order to prevent rupture from a recurrent bAVM and subsequent morbidity.

Embolization as stand-alone strategy for pediatric low-grade brain arteriovenous malformations

OBJECTIVES

We evaluated the safety and efficacy of endovascular embolization as first-line stand-alone strategy for the treatment of low-grade brain arteriovenous malformations (bAVMs) (Spetzler Martin [SM] grade I and II) in pediatric patients. In addition, we assessed the predictors of procedure-related complications and radiographic complete obliteration in a single session.

MATERIAL AND METHODS

We conducted a single center retrospective cohort study of all pediatric (≤18 years) patients who underwent embolization as a stand-alone strategy for low-grade bAVMs between 2010 and 2022. Safety was measured by procedure-related complications and mortality. Efficacy was defined as complete angiographic obliteration after the last embolization session.

RESULTS

Sixty-eight patients (41 females; median age 14 years) underwent a total of 102 embolization sessions. There were 24 (35%) SM grade I lesions and 44 (65%) grade II. Six procedure-related complications (5.8% of procedures) were observed and no deaths were reported. All the complications were intraoperative nidus ruptures. A single draining vein was the only significant predictor of procedure-related complications (OR=0.10; 95% CI 0.01 - 0.72; p=0.048). Complete angiographic obliteration was achieved in 44 patients (65%). In 35 patients (51%) the bAVM was completely occluded in one session. The bAVM nidal size was a predictor of complete obliteration in one session (OR=0.44; 95% CI, 0.21-0.80; p=0.017).

CONCLUSION

Endovascular treatment as a stand-alone strategy for pediatric low-grade bAVMs is an adequate first-line approach in high volume centers with endovascular expertise. Nidal size evaluation is relevant in order to optimize patient selection for embolization as a stand-alone treatment modality.

A complex approach to the treatment of arteriovenous IV-V degree malformations according to Spetzler‒Martin scale. Clinical case

Four therapeutic approaches have been developed for the treatment of arteriovenous malformations (AVMs): microsurgery, radiosurgery, embolization, and conservative treatment. The lack of consensus regarding the choice of treatment method and the different specializations of the doctor who are onvolved to the patient with AVM often determine the wrong treatment strategy. We performed a prospective analysis of the results of AVM of the IV degree according to Spetzler‒Martin scale, 4–5 points on the Buffalo scale complex treatment, based on clinical and tomographic data after the use of partial endovascular embolization and radical microsurgical removal of the AVM node assisted by cell saving technology. According to cerebral angiography 4 months follow-up there is no visible AVM vessels, the malformation was completely resected.Treatment of large and giant AVMs (IV and V degrees according to the Spetzler‒Martin scale) requires tailored surgical treatment approache using endovascular, microsurgical and radiosurgical techniques, but in many cases without achieving a radical result. The use of cell saver technology is necessary to reduce the risks of intraoperative complications associated with blood loss during microsurgical intervention, and enables radical removal of the AVM and recovery of the patient. The role of cell saver technology is crucial in vascular microsurgical interventions, which are often accompanied by a significant volume of blood loss, ensuring rapid autologous hemotransfusion and restoration of circulating blood volume. Endovascular embolization is a necessary step to reduce the risks of intraoperative complications during microsurgical intervention, which, together with the use of cell saver technology, makes it possible to achieve radical AVM removal and patient recovery.

Management of Brain Arteriovenous Malformations: A Review

Brain arteriovenous malformations (bAVM) are vascular malformations of the brain affecting all ages. The optimum management strategy is essentially devoid of high-quality evidence and is highly nuanced and embedded in local customs. This study summarizes the frequently employed management strategies, drawing conclusions on the utility of each method of treatment and delving into controversies surrounding them. A literature search on PubMed and Medline was done on January 3^rd, 2022. 11,767 articles were found, and abstracts were reviewed. Full-text review of 153 articles led to chapters from three books and 71 articles incorporated into a summative discussion. Spetzler-Ponce (S-P) Class A patients may be offered surgery if they are good surgical candidates and have a good number of high-quality years of life left. The exception is diffuse Spetzler-Martin (S-M) grade 2 in a patient older than 40 years: radiosurgery for unruptured and embolization for ruptured. S-P Class B may be offered surgery if a compact nidus or if younger than 40 years. If diffuse or age greater than 40, radiosurgery may be preferred if the Pollock-Flickinger score is less than 2.5. For the remainder of S-P Class B, conservative management may be preferred. S-P Class C is generally not treated unless young or those patients with poorly controlled seizures affecting their quality of life are willing to risk permanent neurological deficits. While the quality of studies is generally high, the level of evidence is concerning with only one randomized controlled trial (RCT). Most research output hails from high-income countries, i.e., perhaps not universally applicable to all settings owing to possible genetic, environmental, and resource differences. More research is needed: large volume studies in the pregnant population, validation of scoring systems in pediatric age groups, clinical trials focused on combination multi-staged treatment modalities, and studies originating from the developing world.

Microsurgery versus Microsurgery With Preoperative Embolization for Brain Arteriovenous Malformation Treatment: A Systematic Review and Meta-analysis

BACKGROUND

Preoperative embolization has traditionally been regarded as a safe and effective adjunct to microsurgical treatment of brain arteriovenous malformations (bAVM). However, there is currently no high-level evidence to ascertain this presumption.

OBJECTIVE

To compare the outcomes of microsurgery (MS) vs microsurgery with preoperative embolization (E + MS) in patients with bAVM through systematic review.

METHODS

We searched MEDLINE, PubMed, and Embase. The primary outcome was bAVM obliteration. Secondary outcomes were intraoperative bleeding (mL), complications, worsened modified Rankin Scale (mRS), and mortality. The pooled proportions of outcomes were calculated through the logit transformation method. The odds ratio (OR) of categorical data and mean difference of continuous data were estimated through the Mantel-Haenszel and the inverse variance methods, respectively.

RESULTS

Thirty-two studies met the eligibility criteria. One thousand eight hundred twenty-eight patients were treated by microsurgery alone, and 1088 were treated by microsurgery with preoperative embolization, respectively. The meta-analysis revealed no significant difference in AVM obliteration (94.1% vs 95.6%, OR = 1.15 [0.63-2.11], P = .65), mortality (1.7% vs 2%, OR = 0.88 [0.30-2.58], P = .82), procedural complications (18.2% vs 27.2%, OR = 0.47 [0.19-1.17], P = .10), worsened mRS (21.2% vs 18.5%, OR = 1.08 [0.33-3.54], P = .9), and intraoperative blood loss (mean difference = 182.89 [-87.76, 453.55], P = .19).

CONCLUSION

The meta-analysis showed no significant difference in AVM obliteration, mortality, complications, worse mRS, and intraoperative blood loss between MS and E + MS groups. For AVMs where MS alone has acceptable results, it is reasonable to bypass unnecessary preoperative embolization given higher postoperative complication risk.

Newer Updates in Pediatric Vascular Diseases

Pediatric neurovascular pathology directly involves or is in close proximity to the central nervous system (CNS). These vascular pathologies can occur in isolation or in association with broader syndromes. While some vascular pathologies are unique to the pediatric population, the full spectrum of adult neurovascular lesions can also affect children however, may present differently both clinically and on diagnostic imaging. Non-invasive (Ultrasound, CT, MRI) imaging plays a critical role in the diagnosis, treatment planning, and follow-up of vascular lesions involving the CNS. The modality can be chosen based on the age of the child, urgency of diagnosis, and local availability. Each modality has sensitivities and specificities which vary based on the location and imaging findings of a specific neurovascular pathology. In addition to non-invasive options, digital subtraction angiography (DSA) may be used as both a diagnostic and therapeutic imaging method for pediatric vascular lesions of the central nervous system. The diagnosis and management of pediatric cerebrovascular disease requires the close collaboration between pediatricians and pediatric specialists including neuroradiologists, neurologists, neurosurgeons, cardiologists, neurointerventionalists, and anesthesiologists among others. A detailed understanding of imaging findings, natural history, and treatment options is essential to guide and monitor imaging and treatment. The goal of this review is to provide the reader with an overview on pediatric neurovascular pathologies, provide examples of pathognomonic imaging findings, and present a brief review of endovascular treatment options, if applicable.

Clinical features and outcome in pediatric arteriovenous malformation: institutional multimodality treatment

PURPOSE

Intracranial arteriovenous-malformation (AVM) is a relatively rare condition in pediatrics, yet is a major cause of spontaneous intracranial hemorrhage with a risk of fatal hemorrhage reported to be between 4 and 29%. Little is known about vessel morphology and optimum treatment modalities including multimodality combination therapy and prognosis in children.

METHODS

A retrospective review of all children presenting to our institution from 2006 to 2020 that had an AVM was undertaken.

RESULTS

A total of 50 children were identified with median age of 11 (range 1-16) years. The mean follow-up was 7.6 years. Forty-one children presented as an emergency and of those, 40 had hemorrhage identified on initial brain imaging. The average nidus size was 25 mm, drainage was superficial in 51% of cases, and located in eloquent cortex in 56%. The supplemental Spetzler-Martin grading indicated 78% (39/50) were grade 4 and above (moderate to high risk). Primary treatment modalities included embolization in 50% (25) or SRS in 30% (15) and surgery in 20% (10).The AVM was obliterated on follow-up DSA in 66% children. Three children had post-treatment hemorrhage, two related to embolization and one the day following SRS, giving a re-bleed rate of 6%. The GOSE was available for 32 children at long term follow and 94% had a good outcome (GOSE 5-8). Two children died due to acute hemorrhage (4%).

CONCLUSION

The majority of children with AVM present with hemorrhage. The rebleed rate during definitive treatment is low at 6% over the study period. The selective use of the 3 modalities of treatment has significantly reduced mortality and severe disability.

State of the Art in the Role of Endovascular Embolization in the Management of Brain Arteriovenous Malformations-A Systematic Review

As a significant cause of intracerebral hemorrhages, seizures, and neurological decline, brain arteriovenous malformations (bAVMs) are a rare group of complex vascular lesions with devastating implications for patients' quality of life. Although the concerted effort of the scientific community has improved our understanding of bAVM biology, the exact mechanism continues to be elucidated. Furthermore, to this day, due to the high heterogeneity of bAVMs as well as the lack of objective data brought by the lack of evaluative and comparative studies, there is no clear consensus on the treatment of this life-threatening and dynamic disease. As a consequence, patients often fall short of obtaining the optimal treatment. Endovascular embolization is an inherent part of multidisciplinary bAVM management that can be used in various clinical scenarios, each with different objectives. Well-trained neuro-interventional centers are proficient at curing bAVMs that are smaller than 3 cm; are located superficially in noneloquent areas; and have fewer, larger, and less tortuous feeding arteries. The transvenous approach is an emerging effective and safe technique that potentially offers a chance to cure previously untreatable bAVMs. This review provides the state of the art in all aspects of endovascular embolization in the management of bAVMs.

Brain AVMs-Related microRNAs: Machine Learning Algorithm for Expression Profiles of Target Genes

INTRODUCTION

microRNAs (miRNAs) are a class of non-coding RNAs playing a myriad of important roles in regulating gene expression. Of note, recent work demonstrated a critical role of miRNAs in the genesis and progression of brain arteriovenous malformations (bAVMs). Accordingly, here we examine miRNA signatures related to bAVMs and associated gene expression. In so doing we expound on the potential prognostic, diagnostic, and therapeutic significance of miRNAs in the clinical management of bAVMs.

METHODS

A PRISMA-based literature review was performed using PubMed/Medline database with the following search terms: "brain arteriovenous malformations", "cerebral arteriovenous malformations", "microRNA", and "miRNA". All preclinical and clinical studies written in English, regardless of date, were selected. For our bioinformatic analyses, miRWalk and miRTarBase machine learning algorithms were employed; the Kyoto Encyclopedia of Genes and Genomes (KEGG) database was quired for associated pathways/functions.

RESULTS

four studies were ultimately included in the final analyses. Sequencing data consistently revealed the decreased expression of miR-18a in bAVM-endothelial cells, resulting in increased levels of vascular endodermal growth factor (VEGF), Id-1, matrix metalloproteinase, and growth signals. Our analyses also suggest that the downregulation of miR-137 and miR-195* within vascular smooth muscle cells (VSMCs) may foster the activation of inflammation, aberrant angiogenesis, and phenotypic switching. In the peripheral blood, the overexpression of miR-7-5p, miR-629-5p, miR-199a-5p, miR-200b-3p, and let-7b-5p may contribute to endothelial proliferation and nidus development. The machine learning algorithms employed confirmed associations between miRNA-related target networks, vascular rearrangement, and bAVM progression.

CONCLUSION

miRNAs expression appears to be critical in managing bAVMs' post-transcriptional signals. Targets of microRNAs regulate canonical vascular proliferation and reshaping. Although additional scientific evidence is needed, the identification of bAVM miRNA signatures may facilitate the development of novel prognostic/diagnostic tools and molecular therapies for bAVMs.

Long-term follow-up in patients with brain arteriovenous malformation based on the Quality of Life Scale and socioeconomic status

OBJECTIVE

Intracranial haemorrhage (ICH) is associated with permanent neurological disability resulting in deterioration of the quality of life (QoL). Our study assesses QoL in patients with ruptured arteriovenous malformation (AVM) in long-term follow-up at least five years after ICH and compares their QoL with the QoL of patient with non-ruptured AVM.

METHODS

Using the Quality of Life Scale (QOLS), the Patient Health Questionnaire (PHQ-9) for depressive symptoms, and the socioeconomic status (SES), a prospective assessment was performed. The modified Rankin Scale (mRS) was assessed for outcome.

RESULTS

Of 73 patients, 42 (57.5%) had ruptured (group 1) and 31 (42.5%) a non-ruptured AVM (group 2). Mean follow-up time was 8.6 ± 3.9 years (8.5 ± 4.2 years in group 1 and 8.9 ± 3.7 years in group 2). Favourable outcome (mRS 0-1) was assessed in 60 (83.3%) and unfavourable in 12 (16.7%) patients. Thirty-one of 42 patients (73.8%) in group 1 and 29 of 30 patients in group 2 (96.7%) had favourable outcomes. Mean QOLS was 85.6 ± 14.1 (group 1 86.1 ± 15.9, group 2 84.9 ± 11.4). Patients in group 1 did not show a significant difference in QoL compared to patients in group 2 (p = 0.23). Additional analyses in group 2 (rho =  - 0.73; p < 0.01) and in untreated AVM patients (rho =  - 0.81; p < 0.01) showed a strong correlation between QOLS and PHQ-9.

CONCLUSION

Long-term follow-up showed no difference in the QoL between patients with and without ICH caused by brain AVM. Outcome- and QoL-scores were high in both groups. Further studies are necessary to evaluate depression and anxiety symptoms in patients with AVM.

Long-term health-related quality of life in patients with ruptured arteriovenous malformations treated in childhood

OBJECTIVE

The aim of this study was to reveal the long-term health-related quality of life (HRQOL), educational level, and impact on occupation in 55 patients who experienced ruptured brain arteriovenous malformations (AVMs) that were treated during childhood.

METHODS

In 2016, questionnaires including the 15D instrument were sent to all living patients older than 18 years (n = 432) in the Helsinki AVM database. The cohort was further specified to include only patients with ruptured AVMs who were younger than 20 years at the time of diagnosis (n = 55). Educational level was compared with the age-matched general population of Finland. The mean 15D scores were calculated for independent variables (Spetzler-Ponce classification, admission age, symptomatic epilepsy, and multiple bleeding episodes) and tested using the independent-samples t-test or ANCOVA. Linear regression was used to create a multivariate model. Bonferroni correction was used with multiple comparisons.

RESULTS

The mean follow-up time from diagnosis to survey was 24.2 (SD 14.7) years. The difference in the mean 15D scores between Spetzler-Ponce classes did not reach statistical significance. The youngest age group (< 10 years at the time of diagnosis) performed less well on the dimension of usual activities than the older patients. Symptomatic epilepsy significantly reduced the long-term HRQOL. Multiple hemorrhages significantly reduced the scores on three dimensions: mobility, speech, and sexual activity. In the regression model, symptomatic epilepsy was the only significant predictor for a lower 15D score. The educational level of the cohort was for the most part comparable to that of the general population in the same age group. AVM was the reason for early retirement in 11% of the patients, while lowered performance because of the AVM was reported by 37% of the patients.

CONCLUSIONS

Patients with ruptured AVMs treated in childhood can live an independent and meaningful life, even in the case of the highest-grade lesions. Symptomatic epilepsy significantly reduced the long-term HRQOL, highlighting the need for continuing support for these patients.

Curative Embolization of Small Brain Arteriovenous Malformations by Ethyl Vinyl Alcohol Copolymer: A Systematic Review and Meta-Analysis

The right choice in treating small (Spetzler-Ponce grade A) brain arteriovenous malformations (AVMs) is a matter of debate with varying views from neurology, neurosurgery, and interventional neuroradiology points of view. The Spetzler-Martin 1 and 2 brain AVMs, especially those in eloquent and deep areas that are difficult to access by micro-neurosurgery, are most suitable for a complete cure by endovascular embolization with ethyl vinyl alcohol (EVOH)-based agents.

A literature search was done with keywords such as endovascular embolization of small brain AVM. Data from 13 articles are included in the study based on predetermined inclusion and exclusion criteria.

Meta-analysis for the complete cure rate was done, publication bias was removed, and regression analysis showed a 76% cure rate with a 95% confidence interval (CI). Major complications were hemorrhage and neurological deficit, which ranged from 0-20% and 0-16% with a mean proportion of 0.11 and 0.09, respectively. Long-term (3-6 months) follow-up data showed 0-4% recurrence at three months, 0-8% recurrence at six months, and 2-10% permanent disability. The mortality rate ranged from 3% to 4%. Three illustrative cases with data from the author’s institute are included in the article. To conclude, endovascular embolization for small brain AVMs is a satisfactory treatment modality, however, prospective registries and randomized controlled trials involving embolization versus neurosurgery and/or stereotactic radiosurgery (SRS) may validate the role of embolization in small brain AVMs as curative treatment.

Long-term outcomes of Spetzler-Martin grade IV and V arteriovenous malformations: a single-center experience

OBJECTIVE

This study aimed to explore whether intervention can benefit Spetzler-Martin (SM) grade IV-V arteriovenous malformations (AVMs).

METHODS

Eighty-two patients with SM grade IV-V AVMs were retrospectively reviewed from 2015 to 2018. Patients were divided into two groups: those who received conservative management (22 cases [26.8%]) and intervention (60 cases [73.2%], including 21 cases of microsurgery, 19 embolization, and 20 hybrid surgery). Neurofunctional outcomes were assessed with the modified Rankin Scale (mRS). The primary outcome was long-term neurofunctional status, and the secondary outcomes were short-term neurofunctional status, long-term obliteration rate, seizure control, and risk of subsequent hemorrhage.

RESULTS

Regarding the primary outcome, after an average of 4.7 years of clinical follow-up, long-term neurofunctional outcomes were similar after conservative management or intervention (absolute difference -0.4 [95% CI -1.5 to 0.7], OR 0.709 [95% CI 0.461-1.090], p = 0.106), whereas intervention had an advantage over conservative management for avoidance of severe disability (defined as mRS score > 3) (1.7% vs 18.2%, absolute difference 16.5% [95% CI -23.6% to 56.6%], OR 0.076 [95% CI 0.008-0.727], p = 0.025). Regarding the secondary outcomes, intervention was conducive to better seizure control (Engel class I-II) (70.0% vs 0.0%, absolute difference 70.0% [95% CI 8.6%-131.4%], p = 0.010) and avoidance of subsequent hemorrhage (1.4% vs 6.0%, absolute difference 4.6% [95% CI -0.4% to 9.6%], p = 0.030). In the subgroup analysis based on different intervention modalities, microsurgery and hybrid surgery achieved higher complete obliteration rates than embolization (p < 0.001), and hybrid surgery resulted in significantly less intraoperative blood loss than microsurgery (p = 0.041).

CONCLUSIONS

Intervention is reasonable for properly indicated SM grade IV-V AVMs because it provides satisfactory seizure control with decreased risks of severe disability and subsequent hemorrhage than conservative management. Clinical trial registration no.: NCT04572568 (ClinicalTrials.gov).

Endovascular treatment in the multimodality management of brain arteriovenous malformations: report of the Society of NeuroInterventional Surgery Standards and Guidelines Committee

BACKGROUND

The purpose of this review is to summarize the data available for the role of angiography and embolization in the comprehensive multidisciplinary management of brain arteriovenous malformations (AVMs METHODS: We performed a structured literature review for studies examining the indications, efficacy, and outcomes for patients undergoing endovascular therapy in the context of brain AVM management. We graded the quality of the evidence. Recommendations were arrived at through a consensus conference of the authors, then with additional input from the full Society of NeuroInterventional Surgery (SNIS) Standards and Guidelines Committee and the SNIS Board of Directors.

RESULTS

The multidisciplinary evaluation and treatment of brain AVMs continues to evolve. Recommendations include: (1) Digital subtraction catheter cerebral angiography (DSA)-including 2D, 3D, and reformatted cross-sectional views when appropriate-is recommended in the pre-treatment assessment of cerebral AVMs. (I, B-NR) . (2) It is recommended that endovascular embolization of cerebral arteriovenous malformations be performed in the context of a complete multidisciplinary treatment plan aiming for obliteration of the AVM and cure. (I, B-NR) . (3) Embolization of brain AVMs before surgical resection can be useful to reduce intraoperative blood loss, morbidity, and surgical complexity. (IIa, B-NR) . (4) The role of primary curative embolization of cerebral arteriovenous malformations is uncertain, particularly as compared with microsurgery and radiosurgery with or without adjunctive embolization. Further research is needed, particularly with regard to risk for AVM recurrence. (III equivocal, C-LD) . (5) Targeted embolization of high-risk features of ruptured brain AVMs may be considered to reduce the risk for recurrent hemorrhage. (IIb, C-LD) . (6) Palliative embolization may be useful to treat symptomatic AVMs in which curative therapy is otherwise not possible. (IIb, B-NR) . (7) The role of AVM embolization as an adjunct to radiosurgery is not well-established. Further research is needed. (III equivocal, C-LD) . (8) Imaging follow-up after apparent cure of brain AVMs is recommended to assess for recurrence. Although non-invasive imaging may be used for longitudinal follow-up, DSA remains the gold standard for residual or recurrent AVM detection in patients with concerning imaging and/or clinical findings. (I, C-LD) . (9) Improved national and international reporting of patients of all ages with brain AVMs, their treatments, side effects from treatment, and their long-term outcomes would enhance the ability to perform clinical trials and improve the rigor of research into this rare condition. (I, C-EO) .

CONCLUSIONS

Although the quality of evidence is lower than for more common conditions subjected to multiple randomized controlled trials, endovascular therapy has an important role in the management of brain AVMs. Prospective studies are needed to strengthen the data supporting these recommendations.

State of the Art and Future Direction in Diagnosis, Molecular Biology, Genetics, and Treatment of Brain Arteriovenous Malformations

Brain arteriovenous malformations (bAVMs) are uncommon and represent a heterogeneous group of lesions. Although these 2 facts have delayed research on this topic, knowledge about the pathophysiology, diagnosis, and treatment of bAVMs has evolved in recent years. We conducted a review of the literature to update the knowledge about diagnosis, molecular biology, genetic, pathology, and treatment by searching for the following terms: "Epidemiology AND Natural History," "risk of hemorrhage," "intracranial hemorrhage," "diagnosis," "angiogenesis," "molecular genetics," "VEGF," "KRAS," "radiosurgery," "endovascular," "microsurgery," or "surgical resection." Our understanding of bAVMs has significantly evolved in recent years. The latest investigations have helped in defining some molecular pathways involved in the pathology of bAVM. Although there is still more to learn and discover, describing these pathways will allow the creation of targeted treatments that could improve the prognosis of patients with bAVMs.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

Comparison of Endovascular Embolization Plus Simultaneous Microsurgical Resection vs. Primary Microsurgical Resection for High-Grade Brain Arteriovenous Malformations

Aim: It remains a challenge in surgical treatments of brain arteriovenous malformations (AVMs) in Spetzler-Martin Grade (SMG) IV and V to achieve both optimal neurological outcomes and complete obliteration. The authors reported a series of patients with AVMs in SMG IV and V who underwent a surgical paradigm of endovascular embolization and simultaneous microsurgical resection based on the one-staged hybrid operation. Methods: Participants in the multicenter prospective clinical trial (NCT03774017) between January 2016 and December 2019 were enrolled. Patients who received endovascular embolization plus microsurgical resection (EE+MRS) and those who received intraoperative digital subtraction angiography plus microsurgical resection (iDSA+MRS) were divided into two groups. Information on clinical features, operative details, and clinical outcomes were extracted from the database. Deterioration of neurological deficits (DNDs) was defined as the primary outcome, which represented neurological outcomes. The time of microsurgical operation and blood loss were defined as the secondary outcomes representing microsurgical risks and difficulties. Outcomes and technical details were compared between groups. Results: Thirty-eight cases (male: female = 23:15) were enrolled, with 24 cases in the EE+MRS group and 14 in the iDSA+MRS group. Five cases (13.2%) were in SMG V and 33 cases (86.8%) were in SMG IV. Fourteen cases (36.8%) underwent the paradigm of microsurgical resection plus intraoperative DSA. Twenty-four cases (63.2%, n = 24) underwent the paradigm of endovascular embolization plus simultaneous microsurgical resection. Degradations of SMG were achieved in 15 cases. Of the cases, two cases got the residual nidus detected via intraoperative DSA and resected. Deterioration of neurological deficits occurred in 23.7% of cases (n = 9) when discharged, and in 13.5, 13.5, 8.1% of cases at the follow-ups of 3, 6, and 12 months, respectively, without significant difference between groups (P > 0.05). Intracranial hemorrhagic complications were reported in three cases (7.9%) of the EE+MRS group only. The embolization did not significantly affect the surgical time and intraoperative blood loss. The subtotal embolization or the degradation of size by 2 points resulted in no DNDs. Conclusions: The paradigms based on the one-staged hybrid operation were practical and effective in treating high-grade AVMs. Appropriate intraoperative embolization could help decrease operative risks and difficulties and improve neurological outcomes.

Complete seizure-free rates following interventional treatment of intracranial arteriovenous malformations: a systematic review and meta-analysis

Seizures are common presenting symptoms of intracranial arteriovenous malformations (AVMs). This systematic review and meta-analysis aims to assess the current evidence regarding complete seizure freedom rates following surgical resection, stereotactic radiosurgery (SRS), and/or endovascular embolization of intracranial AVMs. A systematic review of PubMed, Ovid MEDLINE, and Ovid EMBASE was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included manuscripts were methodically scrutinized for quality, spontaneous AVM-associated or hemorrhage-associated seizures, complete seizure-free rates following each interventional treatment, follow-up duration; determination methods of seizure outcomes, and average time-to-onset of recurrent seizures after each treatment. Manuscripts that described patients with nondisabling seizures or reduced seizure frequency in their seizure-free calculations were excluded. Seizure freedom rates following surgical resection, SRS, and endovascular embolization were compared via random-effect analysis. Thirty-four studies with a total of 1765 intracranial AVM patients presenting with spontaneous AVM-associated seizures and 408 patients presenting with hemorrhage-associated seizures were qualitatively analyzed. For patients presenting with AVM-associated seizures, the complete seizure-free rates were 73.0% (321/440 patients; 95% CI 68.8-77.1%) following surgical resection, 60.5% (376/622 patients; 95% CI 56.6-64.3%) following SRS, and 44.6% (29/65 patients; 95% CI 32.5-56.7%) following endovascular embolization alone. For patients presenting with either AVM-associated or hemorrhage-associated seizures, the complete seizure-free rates were 73.0% (584/800 patients; 95% CI 69.9-76.1%) following surgical resection, 46.4% (572/1233 patients; 95% CI 43.6-49.2%) following SRS, and 44.6% (29/65 patients; 95% CI 32.5-56.7%) following embolization. For patients presenting with either AVM-associated or hemorrhage-associated seizures, the overall improvements in seizure outcomes regardless of complete seizure freedom were 82.6% (661/800 patients; 95% CI 80.0-85.3%), 70.6% (870/1233 patients; 95% CI 68.0-73.1%), and 70.8% (46/65 patients; 95% CI 59.7-81.1%) following surgical resection, SRS, and embolization, respectively. No study reported information about the time-to-onset for recurrent seizures in any patient following treatment, as seizure outcomes were only described at the last follow-up visit. The available data suggests that surgical resection results in the highest rate of complete seizure freedom. The rate of seizure improvement following surgery increased further to 82.3% when including patients who had improved seizure frequency without achieving true seizure freedom. Complete seizure-free rates following SRS or embolization were more ambiguous and lower when compared to surgical resection. There is a need for high quality studies evaluating AVM treatment modalities and clearly defined seizure outcomes, as the current literature consists mostly of heterogenous patient populations.

4D Flat Panel Conebeam CTA for Analysis of the Angioarchitecture of Cerebral AVMs with a Novel Software Prototype

BACKGROUND AND PURPOSE

Time-resolved 3DRA (4D-DSA) and flat panel conebeam CTA are new methods for visualizing the microangioarchitecture of cerebral AVMs. We applied a 4D software prototype to a series of cases of AVMs to assess the utility of this method in relation to treatment planning.

MATERIALS AND METHODS

In 33 patients with AVMs, 4D volumes and flat panel conebeam CTA images were recalculated from existing 3D rotational angiography data. The multiplanar reconstructions were used to determine intranidal arteriovenous branching patterns, categorize them according to common classifications of AVM angioarchitecture, and compare the results with those from 2D-DSA.

RESULTS

4D flat panel conebeam CTA showed angioarchitectural features equal to or better than those of 2D-DSA in 30 of 33 cases. In particular, the reconstructions helped in understanding the intranidal microvasculature. Fistulous direct arteriovenous connections with a low degree of arterial branching (n = 22) could be distinguished from plexiform arterial networks before the transition to draining veins (n = 11). We identified AVMs with a single draining vein (n = 20) or multiple draining veins (n = 10). Arteriovenous shunts in the lateral wall of the draining veins (n = 22) could be distinguished from cases with increased venous branching and shunts between corresponding intranidal arteries and veins (n = 11). Limitations were the time-consuming postprocessing and the difficulties in correctly tracing intranidal vessels in larger and complex AVMs.

CONCLUSIONS

4D flat panel conebeam CTA reconstructions allow detailed analysis of the nidal angioarchitecture of AVMs. However, further improvements in temporal resolution and automated reconstruction techniques are needed to use the method generally in clinical practice.

Effects of Preoperative Embolization on Spetzler-Martin Grade I and II Arteriovenous Malformations: A Propensity-Adjusted Analysis

BACKGROUND

Cerebral arteriovenous malformations (AVMs) with low Spetzler-Martin grades (I and II) are associated with good neurological outcomes after microsurgical resection; however, the use of preoperative embolization for these lesions is controversial.

OBJECTIVE

To compare the neurological outcomes of preoperative embolization with no embolization in patients with low-grade AVMs.

METHODS

Patients with a Spetzler-Martin grade I or II AVM who underwent microsurgical resection during January 1, 1997, through December 31, 2019, were analyzed. Patients undergoing preoperative embolization were compared with patients not undergoing embolization. A propensity score was constructed from baseline characteristics and used to match intervention (embolization) and control (nonembolization) groups in a 1:1 ratio. The primary outcome was poor neurological status on last follow-up examination, defined as a modified Rankin Scale score >2 and a modified Rankin Scale score worse at follow-up than at the preoperative examination.

RESULTS

Of the 603 patients analyzed, 310 (51.4%) underwent preoperative embolization and 293 (48.6%) did not. Patients in the embolization cohort compared with those in the nonembolization cohort had a higher percentage of Spetzler-Martin grade II AVMs (71.6% vs 52.6%, P < .001) and a lower percentage of hemorrhage (41% vs 55%, P = .001). After propensity score matching, no differences were found between paired cohorts (each N = 203) for baseline characteristics with a significant reduction in absolute standardized mean differences. No significant differences were found in primary outcomes between treatment groups in the matched or unmatched cohorts.

CONCLUSION

Preoperative embolization of low-grade Spetzler-Martin AVMs is not associated with improved neurological outcomes after microsurgical resection.

A Ruptured Spetzler and Martin Grade V Arteriovenous Malformation in a Child Treated With Radiotherapy Followed by Embolization: A Case Report and Literature Review

Treatment of ruptured high-grade Spetzler-Martin (S&M) arteriovenous malformation (AVM) is challenging and requires a multidisciplinary treatment approach. Here, we report a case of ruptured giant callosal Grade V AVM in a child initially treated with stereotactic radiotherapy followed by endovascular embolization with Onyx; a management approach recently described in a few reports on the “postradiosurgical embolization” method. Complete obliteration was achieved 20 months after stereotactic radiotherapy and embolization. In this article, we discuss the usefulness and significance of postradiosurgical embolization, particularly for high-grade AVMs. To our knowledge, this is the first case with a giant Spetzler-Martin Grade V AVM treated with a postradiosurgical embolization method.

Spetzler-Martin Grade III Arteriovenous Malformations: A Comparison of Modified and Supplemented Spetzler-Martin Grading Systems

BACKGROUND

The modified Spetzler-Martin (SM) grading system proposes that grade III arteriovenous malformation (AVM) subtypes are associated with variable microsurgical risks, with small AVMs (III-) having lower risk and medium/eloquent AVMs (III+) having higher risk. Adding patient age and AVM bleeding status and compactness to the SM grade produces a score - the supplemented SM (Supp-SM) grade - to more accurately assess preoperative risk.

OBJECTIVE

To compare the predictive power of the modified SM and Supp-SM grades for risk assessment in patients with grade III AVMs.

METHODS

Patients with SM grade III AVMs treated between 2011 and 2018 were retrospectively reviewed. Good outcomes were defined as modified Rankin Scale (mRS) scores ≤ 2 or unchanged/improved mRS scores (pre- vs postsurgery).

RESULTS

Of 102 patients with SM grade III AVMs, 59% had grade III- and 24% had grade III+ AVMs. Supp SM grade 6 and grade 7 AVMs accounted for 44% and 24%, respectively. Overall, 33% of patients worsened but outcomes did not significantly differ by SM III subtype. Neurological outcomes were associated with Supp-SM grade, with proportions of patients with worsening increasing from 0% with Supp-SM grade 4 AVMs to 54% with Supp-SM grade 7 AVMs. Analyses of factors associated with neurological worsening identified age > 60 yr and Supp-SM grade 7 as significant.

CONCLUSION

Supp-SM grades were more predictive of microsurgical outcomes than modified SM grades for grade III AVMs, with a hard cutoff for acceptable surgical risk at Supp-SM grade 6. Supp-SM grading is a better decision-making tool than subtyping with the modified SM scale.

Spetzler-Martin Grade III Arteriovenous Malformations: A Multicenter Propensity-Adjusted Analysis of the Effects of Preoperative Embolization

BACKGROUND

Spetzler-Martin (SM) grade III arteriovenous malformations (AVMs) are at the boundary of safe operability, and preoperative embolization may reduce surgical risks.

OBJECTIVE

To evaluate the benefits of preoperative AVM embolization by comparing neurological outcomes in patients with grade III AVMs treated with or without preoperative embolization.

METHODS

All microsurgically treated grade III AVMs were identified from 2011 to 2018 at 2 medical centers. Neurological outcomes, measured as final modified Rankin Scale scores (mRS) and changes in mRS from preoperative baseline to last follow-up evaluation, were compared in patients with and without preoperative embolization.

RESULTS

Of the 102 patients with grade III AVMs who were treated microsurgically, 57 (56%) underwent preoperative embolization. Significant differences were found between the patients with and without embolization in AVM eloquence (74% vs 93%, P = .02), size ≥ 3 cm (47% vs 73%, P = .01), diffuseness (7% vs 22%, P = .04), and mean final mRS (1.1 vs 2.0, P = .005). Poor outcomes were more frequent in patients without embolization (38%) than with embolization (7%) (final mRS > 2; P < .001). Propensity-adjusted analysis revealed AVM resection without embolization was a risk factor for poor outcome (mRS score > 2; odds ratio, 4.2; 95% CI, 1.1-16; P = .03).

CONCLUSION

Nonembolization of SM grade III AVMs is associated with an increased risk of poor neurological outcomes after microsurgical resection. Preoperative embolization of intermediate-grade AVMs selected because of large AVM size, surgical inaccessibility of feeding arteries, and high flow should be employed more often than anticipated, even in the context of increasing microsurgical experience with AVMs.

Patient functional outcomes and quality of life after surgery for unruptured brain arteriovenous malformation

BACKGROUND

Studies have questioned the effectiveness of surgery for the management of unruptured brain arteriovenous malformation (ubAVM). Few studies have examined functional outcomes and quality of life (QOL) prior and 12 months after surgical repair of ubAVM.

OBJECTIVE

This study examined the effectiveness of surgical management of ubAVM by measuring patients' perceived QOL and their ability to perform everyday activities.

METHODS

Between 2011 and 2016, patients diagnosed with an unbAVM were assessed using the Quality Metric Short Form 36 (SF36), the DriveSafe component of the off-road driver screening tool DriveSafeDriveAware (DSDA), the modified Barthel Index (mBI) and the modified Rankin Scale (mRS). Reassessments were conducted at the 6-week post-operative follow-up for surgical patients and at 12-month follow-up for surgical and conservatively managed patients.

RESULTS

Forty-five patients enrolled in the study, of which 35 (78%) had their ubAVM surgically treated. Patients undergoing surgery had a significantly lower ubAVM Spetzler-Ponce Class (SPC). There was no significant difference 12 months after presentation in function or QOL for either the conservative or surgical group. The surgical group had significantly higher QOL of life scores from pre-surgery to 12 months post-surgery (PCS p < 0.01; MCS p = 0.02). Higher SP grade ubAVM was significantly related to poorer function in the surgical group (SP C compared with SP A; p = 0.04, mean difference - 12.4, 95%CI - 24.3 to - 0.4).

CONCLUSION

Function and QOL are not diminished after surgical treatment of low Spetzler-Ponce Class unruptured brain arteriovenous malformations. QOL is higher 12 months after surgery for ubAVM than for those who do not have treatment for their ubAVM.

Intermediate-grade brain arteriovenous malformations and the boundary of operability using the supplemented Spetzler-Martin grading system

OBJECTIVE

Supplemented Spetzler-Martin grading (Supp-SM), which is the combination of Spetzler-Martin and Lawton-Young grades, was validated as being more accurate than stand-alone Spetzler-Martin grading, but an operability cutoff was not established. In this study, the authors surgically treated intermediate-grade AVMs to provide prognostic factors for neurological outcomes and to define AVMs at the boundary of operability.

METHODS

Surgically treated Supp-SM intermediate-grade (5, 6, and 7) AVMs were analyzed from 2011 to 2018 at two medical centers. Worsened neurological outcomes were defined as increased modified Rankin Scale (mRS) scores on postoperative examinations. A second analysis of 2000-2011 data for Supp-SM grade 6 and 7 AVMs was performed to determine the subtypes with improved or unchanged outcomes. Patients were separated into three groups based on nidus size (S1: < 3 cm, S2: 3-6 cm, S3: > 6 cm) and age (A1: < 20 years, A2: 20-40 years, A3: > 40 years), followed by any combination of the combined supplemented grade: low risk (S1A1, S1A2, S2A1), intermediate risk (S2A2, S1A3, S3A1, or high risk (S3A3, S3A2, S2A3).

RESULTS

Two hundred forty-six patients had intermediate Supp-SM grade AVMs. Of these patients, 102 had Supp-SM grade 5 (41.5%), 99 had Supp-SM grade 6 (40.2%), and 45 had Supp-SM grade 7 (18.3%). Significant differences in the proportions of patients with worse mRS scores at follow-up were found between the groups, with 24.5% (25/102) of patients in Supp-SM grade 5, 29.3% (29/99) in Supp-SM grade 6, and 57.8% (26/45) in Supp-SM grade 7 (p < 0.001). Patients with Supp-SM grade 7 AVMs had significantly increased odds of worse postoperative mRS scores (p < 0.001; OR 3.7, 95% CI 1.9-7.3). In the expanded cohort of 349 Supp-SM grade 6 AVM patients, a significantly higher proportion of older patients with larger Supp-SM grade 6 AVMs (grade 6+, 38.6%) had neurological deterioration than the others with Supp-SM grade 6 AVMs (22.9%, p = 0.02). Conversely, in an expanded cohort of 197 Supp-SM grade 7 AVM patients, a significantly lower proportion of younger patients with smaller Supp-SM grade 7 AVMs (grade 7-, 19%) had neurological deterioration than the others with Supp-SM grade 7 AVMs (44.9%, p = 0.01).

CONCLUSIONS

Patients with Supp-SM grade 7 AVMs are at increased risk of worse postoperative neurological outcomes, making Supp-SM grade 6 an appropriate operability cutoff. However, young patients with small niduses in the low-risk Supp-SM grade 7 group (grade 7-) have favorable postoperative outcomes. Outcomes in Supp-SM grade 7 patients did not improve with surgeon experience, indicating that the operability boundary is a hard limit reflecting the complexity of high-grade AVMs.