Stereotactic radiosurgery for arteriovenous malformations of the basal ganglia and thalamus: an international multicenter study

Radiosurgery With Prior Embolization Versus Radiosurgery Alone for Intracranial Arteriovenous Malformations: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

The addition of adjuvant embolization to radiosurgery has been proposed as a means of improving treatment outcomes of intracranial arteriovenous malformations (AVMs). However, the relative efficacy and safety of radiosurgery with adjuvant embolization vs radiosurgery alone remain uncertain. Moreover, previous systematic reviews and meta-analyses have included a limited number of studies and did not consider the effects of baseline characteristics, including AVM volume, on the outcomes. This systematic review aimed to evaluate the efficacy of preradiosurgery embolization for intracranial AVMs with consideration to matching status between participants in each treatment group.

METHODS

A systematic review and meta-analysis were conducted by searching electronic databases, including PubMed, Scopus, and Cochrane Library, up to January 2023. All studies evaluating the utilization of preradiosurgery embolization were included.

RESULTS

A total of 70 studies (9 matched and 71 unmatched) with a total of 12 088 patients were included. The mean age of the included patients was 32.41 years, and 48.91% of the patients were female. Preradiosurgery embolization was used for larger AVMs and patients with previous hemorrhage ( P < .01, P = .02, respectively). The obliteration rate for preradiosurgery embolization (49.44%) was lower compared with radiosurgery alone (61.42%, odds ratio = 0.56, P < .01), regardless of the matching status of the analyzed studies. Although prior embolization was associated higher rate of cyst formation ( P = .04), it lowered the odds of radiation-induced changes ( P = .04). The risks of minor and major neurological deficits, postradiosurgery hemorrhage, and mortality were comparable between groups.

CONCLUSION

This study provides evidence that although preradiosurgery embolization is a suitable option to reduce the AVM size for future radiosurgical interventions, it may not be useful for same-sized AVMs eligible for radiosurgery. Utilization of preradiosurgery embolization in suitable lesions for radiosurgery may result in the added cost and burden of an endovascular procedure.

Endovascular embolization for basal ganglia and thalamic arteriovenous malformations

Background

Basal ganglia and thalamic arteriovenous malformations (AVMs) represent a special subset of malformations. Due to the involvement of vital brain structures and the specifically fine and delicate angioarchitecture of these lesions, it presents unique therapeutic challenges and technical difficulties that require thorough treatment planning, individualized treatment strategies, and advanced techniques for good clinical outcome.

Method

In this study, we presented a series of ruptured basal ganglia and thalamic AVMs embolized via a transarterial, transvenous or combined approach. Herein, we summarized our treatment experience and clinical outcomes to further evaluate the effectiveness and safety of endovascular embolization for these AVMs as well as the indications, therapy strategies, and techniques of embolization procedures.

Results

Twelve patients with basal ganglia and thalamus AVMs were included in the study. Their average age was 23.83 ± 16.51 years (range, 4-57 years) with a female predominance of 67% at presentation. The AVMs were located in the thalamus in 3 (25%) patients, in the basal ganglia in 3 (25%) patients, and in both sites of the brain in 6 (50%) patients. There were 5 AVMs located on the left side and 7 on the right. The mean nidus diameter was 3.32 ± 1.43 cm (range 1.3-6.1 cm). According to the Spetzler-Martin grading classification, 4 (33.3%) brain AVMs were Grade III, 7 (58.3%) were Grade IV, and 1 (8.3%) was Grade V. All of them presented with bleeding at admission: four of these patients presented with an intracerebral hemorrhage (ICH), 8 ICH in combination with intraventricular hemorrhage (IVH), and no patient with subarachnoid hemorrhage (SAH). Among these patients treated with endovascular embolization, 7 patients were treated by the transarterial approach, 4 patients transvenous approach, and 1 patient underwent the combined approach. A single embolization procedure was performed in 6 patients (50%) and the other 6 cases (50%) were treated in a staged manner with up to three procedures. Procedure-related complications occurred only in two patient (16.7%). Complete AVM obliteration was obtained in 7 patients (58.3%), and partial obliteration was in 4 patients (33.3%). Overall, good or excellent outcomes were obtained in 7 patients (58.3%), and poor functional outcome was observed in 5 patients (41.7%) at the last follow-up. All survived patients achieved anatomic stabilization and there was no postoperative bleeding or recurrence in the follow-up.

Conclusion

The management of the basal ganglia and thalamic AVMs is a great challenge, which needs multimodal individualized treatment to improve the chances of radiographic cure and good outcomes. Endovascular therapy is safe and effective in the treatment of cerebral AVMs particularly for deep-seated AVMs such as the basal ganglia and thalamus. Our results demonstrate a high rate of anatomic obliteration with an acceptable rate of complications in the endovascular treatment of these vasculopathies via a transarterial approach or a transvenous approach.

Stereotactic radiosurgery outcome for deep-seated cerebral arteriovenous malformations in the brainstem and thalamus/basal ganglia: systematic review and meta-analysis

Deep-seated unruptured AVMs located in the thalamus, basal ganglia, or brainstem have a higher risk of hemorrhage compared to superficial AVMs and surgical resection is more challenging. Our systematic review and meta-analysis provide a comprehensive summary of the stereotactic radiosurgery (SRS) outcomes for deep-seated AVMs. This study follows the guidelines set forth by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Statement. We conducted a systematic search in December 2022 for all reports of deep-seated arteriovenous malformations treated with SRS. Thirty-four studies (2508 patients) were included. The mean obliteration rate in brainstem AVM was 67% (95% CI: 0.60-0.73), with significant inter-study heterogeneity (tau2 = 0.0113, I2 = 67%, chi2 = 55.33, df = 16, p-value < 0.01). The mean obliteration rate in basal ganglia/thalamus AVM was 65% (95% CI: 0.58-0.72) with significant inter-study heterogeneity (tau2 = 0.0150, I2 = 78%, chi2 = 81.79, df = 15, p-value < 0.01). The presence of deep draining veins (p-value: 0.02) and marginal radiation dose (p-value: 0.04) were positively correlated with obliteration rate in brainstem AVMs. The mean incidence of hemorrhage after treatment was 7% for the brainstem and 9% for basal ganglia/thalamus AVMs (95% CI: 0.05-0.09 and 95% CI: 0.05-0.12, respectively). The meta-regression analysis demonstrated a significant positive correlation (p-value < 0.001) between post-operative hemorrhagic events and several factors, including ruptured lesion, previous surgery, and Ponce C classification in basal ganglia/thalamus AVMs. The present study found that radiosurgery appears to be a safe and effective modality in treating brainstem, thalamus, and basal ganglia AVMs, as evidenced by satisfactory rates of lesion obliteration and post-surgical hemorrhage.

Transvenous embolization of a ruptured thalamic arteriovenous malformation supplied by the tuberothalamic artery

Background

Basal ganglia and thalamic arteriovenous malformations (AVM) represent 10% of all AVM. They are associated with a high rate of morbidity and mortality due to their high hemorrhagic presentation and eloquence. Radiosurgery has been the first line treatment, whereas surgical removal and endovascular therapy are possible in selected cases. Deep AVM with small niduses and a single draining vein can achieve cure with embolization.

Case Description

A 10-year-old boy with sudden headache and vomiting underwent a brain computed tomography scan that showed a right thalamic hematoma. Cerebral angiography revealed a small ruptured right anteromedial thalamic AVM with a single feeder arising from the tuberothalamic artery and a single drainage to the superior thalamic vein. Transvenous approach using precipitating hydrophobic injectable liquid 25%^® achieved a complete obliteration of the lesion in a single-session. He was discharged home without neurological sequelae and maintained clinically intact at follow-up.

Conclusion

Transvenous embolization of deep-located AVM as a primary treatment is curative in selected cases, with complication rates comparable to other therapeutic strategies.

New aneurysm formation and regrowth associated with rebleeding of residual pediatric ruptured arteriovenous malformation: patient series

BACKGROUND

If complete obliteration of ruptured pediatric arteriovenous malformation (AVM) cannot be achieved, the appropriate follow-up duration and predictors of rebleeding remain unknown.

OBSERVATIONS

Pediatric patients with ruptured AVMs admitted to the authors' hospital within the past 30 years were evaluated. Rebleeding was confirmed in two patients. The first patient was a 5-year-old boy who experienced right thalamic hemorrhage. AVM was found in the bilateral thalamus and treated with stereotactic radiosurgery (SRS). New aneurysm formation and residual AVM regrowth were confirmed 21 years after the SRS. Eight months later, rebleeding occurred. The second patient was a 5-year-old boy who underwent removal of a left cerebellar hemorrhage and AVM. The residual AVM was treated with SRS. Residual AVM regrowth was detected at 6 years 7 months after SRS. Five months later, new aneurysm formation was confirmed. Two additional days later, rebleeding occurred.

LESSONS

New aneurysm formation and residual AVM regrowth may predict rebleeding and can occur >20 years after the initial rupture and treatment. If AVM obliteration is not achieved, long-term follow-up is needed, even in adulthood, with attention to new aneurysm formation and residual AVM regrowth. Further treatment is recommended if these findings are confirmed.

Stereotactic Radiosurgery Provides Long-Term Safety for Patients With Arteriovenous Malformations in the Diencephalon and Brainstem: The Optimal Dose Selection and Long-Term Outcomes

BACKGROUND

Arteriovenous malformations (AVMs) of the diencephalon (DC) and brainstem (BS) are difficult to treat. Stereotactic radiosurgery (SRS) is a reasonable option; however, an optimal radiosurgical dose needs to be established to optimize long-term outcomes.

OBJECTIVE

To evaluate dose-dependent long-term outcomes of SRS for DC/BS-AVMs.

METHODS

We retrospectively analyzed the long-term outcomes of 118 patients who had SRS-treated DC/BS-AVMs. The outcomes included post-SRS hemorrhage, AVM obliteration, neurological outcomes, and disease-specific survival. According to margin doses, the patients were classified into low (<18 Gy), medium (18-20 Gy), and high (>20 Gy) dose groups.

RESULTS

SRS reduced the annual hemorrhage rate from 8.6% to 1.6% before obliteration and 0.0% after obliteration. The cumulative hemorrhage rate in the low dose group was likely to be higher than that in the other groups ( P = .113). The cumulative obliteration rates in the entire cohort were 74% and 83% at 5 and 10 years, respectively, and were significantly lower in the low dose group than in the other groups (vs medium dose: P = .027, vs high dose: P = .016). Multivariate analyses demonstrated that low dose SRS was significantly associated with worse obliteration rates (hazard ratio 0.18, 95% CI 0.04-0.79; P = .023).

CONCLUSION

SRS with a margin dose of 18 to 20 Gy for DC/BS-AVMs may be optimal, providing a higher obliteration rate and lower risk of post-SRS hemorrhage than lower dose SRS. Dose reduction to <18 Gy should only be optional when higher doses are intolerable.

Intracranial arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) has evolved over the last 10 years. It is now possible to see that obliteration continues for up to 10 years and that the final obliteration rate may be between 85% and 90%. Improved imaging has made the treatment more efficient and has reduced the complications. It is possible to treat larger AVMs in a single session than was previously thought possible without increases in the complication rates. In addition, treatments of larger lesions can be staged. The use of 3D rotating angiography produces remarkable images which can be imported into GammaPlan. On the other hand efforts are ongoing to avoid the need for digital subtraction angiography, which would make the treatment a lot more comfortable.

Stereotactic Radiosurgery With vs. Without Prior Embolization for Brain Arteriovenous Malformations: A Propensity Score Matching Analysis

Objective: Whether partial embolization could facilitate the post-stereotactic radiosurgery (SRS) obliteration for brain arteriovenous malformations (bAVMs) remains controversial. We performed this study to compare the outcomes of SRS with and without prior embolization for bAVMs.

Methods: We retrospectively reviewed the Beijing Tiantan AVMs prospective registration research database from September 2011 to October 2014. Patients were categorized into two groups, combined upfront embolization and SRS (Em+SRS group) and SRS alone (SRS group), and we performed a propensity score matching analysis based on pre-embolization baseline characteristics; the matched groups each comprised 76 patients.

Results: The obliteration rate was similar between SRS and Em+SRS (44.7 vs. 31.6%; OR, 1.754; 95% CI, 0.905–3.401; p = 0.096). However, the SRS group was superior to the Em+SRS group in terms of cumulative obliteration rate at a follow-up of 5 years (HR,1.778; 95% CI, 1.017–3.110; p = 0.033). The secondary outcomes, including functional state, post-SRS hemorrhage, all-cause mortality, and edema or cyst formation were similar between the matched cohorts. In the ruptured subgroup, the SRS group could achieve higher obliteration rate than Em+SRS group (56.5 vs. 31.9%; OR, 2.773; 95% CI, 1.190–6.464; p = 0.018). The cumulative obliteration rate at 5 years was also higher in the SRS group (64.5 vs. 41.3%; HR, 2.012; 95% CI, 1.037–3.903; p = 0.038), and the secondary outcomes were also similar between the matched cohorts.

Conclusion: Although there was no significant difference in the overall obliteration rate between the two strategies, this study suggested that pre-SRS embolization may have a negative effect on post-SRS obliteration. Furthermore, the obliteration rates of the SRS only strategy was significantly higher than that of the Em+SRS strategy in the ruptured cohort, while no such phenomenon was found in the unruptured cohort.

Comparison of management approaches in deep-seated intracranial arteriovenous malformations: Does treatment improve outcome?

Deep-seated intracranial arteriovenous malformations (AVMs) represent a subset of AVMs characterized by variably reported outcomes regarding the risk of hemorrhage, microsurgical complications, and response to stereotactic radiosurgery (SRS). We aimed to compare outcomes of microsurgery, SRS, endovascular therapy, and conservative follow-up in deep-seated AVMs. A prospectively maintained database of AVM patients (1990-2017) was queried to identify patients with ruptured and unruptured deep-seated AVMs (extension into thalamus, basal ganglia, or brainstem). Comparisons of hemorrhage-free survival and poor functional outcome (modified Rankin scale [mRS] > 2) were performed between conservative management, microsurgery (±pre-procedural embolization), SRS (±pre-procedural embolization), and embolization utilizing multivariable Cox and logistic regression analyses controlling for univariable factors with p < 0.05. Of 789 AVM patients, 102 had deep-seated AVMs (conservative: 34; microsurgery: 6; SRS: 54; embolization: 8). Mean follow-up time was 6.1 years and did not differ significantly between management groups (p = 0.393). Complete obliteration was achieved in 49% of SRS patients. Upon multivariable analysis controlling for baseline rupture with conservative management as a reference group, embolization was associated with an increased hazard of hemorrhage (HR = 6.2, 95%CI [1.1-40.0], p = 0.037), while microsurgery (p = 0.118) and SRS (p = 0.167) provided no significant protection from hemorrhage. Controlling for baseline mRS, microsurgery was associated with an increased risk of poor outcome (OR = 9.2[1.2-68.3], p = 0.030), while SRS (p = 0.557) and embolization (p = 0.541) did not differ significantly from conservative management. Deep AVMs harbor a high risk of hemorrhage, but the benefit from intervention Remains uncertain. SRS may be a relatively more effective approach if interventional therapy is indicated.

Chinese Cerebrovascular Neurosurgery Society and Chinese Interventional & Hybrid Operation Society, of Chinese Stroke Association Clinical Practice Guidelines for Management of Brain Arteriovenous Malformations in Eloquent Areas

Aim: The aim of this guideline is to present current and comprehensive recommendations for the management of brain arteriovenous malformations (bAVMs) located in eloquent areas. Methods: An extended literature search on MEDLINE was performed between Jan 1970 and May 2020. Eloquence-related literature was further screened and interpreted in different subcategories of this guideline. The writing group discussed narrative text and recommendations through group meetings and online video conferences. Recommendations followed the Applying Classification of Recommendations and Level of Evidence proposed by the American Heart Association/American Stroke Association. Prerelease review of the draft guideline was performed by four expert peer reviewers and by the members of Chinese Stroke Association. Results: In total, 809 out of 2,493 publications were identified to be related to eloquent structure or neurological functions of bAVMs. Three-hundred and forty-one publications were comprehensively interpreted and cited by this guideline. Evidence-based guidelines were presented for the clinical evaluation and treatment of bAVMs with eloquence involved. Topics focused on neuroanatomy of activated eloquent structure, functional neuroimaging, neurological assessment, indication, and recommendations of different therapeutic managements. Fifty-nine recommendations were summarized, including 20 in Class I, 30 in Class IIa, 9 in Class IIb, and 2 in Class III. Conclusions: The management of eloquent bAVMs remains challenging. With the evolutionary understanding of eloquent areas, the guideline highlights the assessment of eloquent bAVMs, and a strategy for decision-making in the management of eloquent bAVMs.

Predictive Factors of Radiation-Induced Changes Following Single-Session Gamma Knife Radiosurgery for Arteriovenous Malformations

We evaluated for possible predictors of radiation-induced changes (RICs) after gamma knife radiosurgery (GKRS) for arteriovenous malformations (AVMs). We identified the nidal component within AVMs to analyze the correlation between the volume of brain parenchyma within the 50% isodose line (IDL) and RICs. We retrospectively reviewed patients with AVMs who underwent a single-session of GKRS at our institution between 2007 and 2017 with at least a 2-year minimum follow-up. Follow-up magnetic resonance images were evaluated for newly developed T2 signal changes and the proportions of nidus and intervening parenchyma were quantified. A total of 180 AVM patients (98 males and 82 females) with a median age of 34 years were included in the present study. The overall obliteration rate was 67.8%. The median target volume was 3.65 cc. The median nidus and parenchyma volumes within the 50% IDL were 1.54 cc and 2.41 cc, respectively. RICs were identified in 79 of the 180 patients (43.9%). AVMs associated with previous hemorrhages showed a significant inverse correlation with RICs. In a multivariate analysis, RICs were associated with a higher proportion of brain parenchyma within the 50% IDL (hazard ratio (HR) 169.033; p < 0.001) and inversely correlated with the proportion of nidus volume within the 50% IDL (HR 0.006; p < 0.001). Our study identified that a greater proportion of brain tissue between the nidus within the 50% IDL was significantly correlated with RICs. Nidus angioarchitectural complexity and the absence of a prior hemorrhage were also associated with RICs. The identification of possible predictors of RICs could facilitate radiosurgical planning and treatment decisions as well as the planning of appropriate follow-up after GKRS; this could minimize the risk of RICs, which would be particularly beneficial for the treatment of incidentally found asymptomatic AVMs.

Stereotactic Radiosurgery for Spetzler-Martin Grade I and II Arteriovenous Malformations: International Society of Stereotactic Radiosurgery (ISRS) Practice Guideline

BACKGROUND

No guidelines have been published regarding stereotactic radiosurgery (SRS) in the management of Spetzler-Martin grade I and II arteriovenous malformations (AVMs).

OBJECTIVE

To establish SRS practice guidelines for grade I-II AVMs on the basis of a systematic literature review.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant search of Medline, Embase, and Scopus, 1986-2018, for publications reporting post-SRS outcomes in ≥10 grade I-II AVMs with a follow-up of ≥24 mo. Primary endpoints were obliteration and hemorrhage; secondary outcomes included Spetzler-Martin parameters, dosimetric variables, and “excellent” outcomes (defined as total obliteration without new post-SRS deficit).

RESULTS

Of 447 abstracts screened, 8 were included (n = 1, level 2 evidence; n = 7, level 4 evidence), representing 1102 AVMs, of which 836 (76%) were grade II. Obliteration was achieved in 884 (80%) at a median of 37 mo; 66 hemorrhages (6%) occurred during a median follow-up of 68 mo. Total obliteration without hemorrhage was achieved in 78%. Of 836 grade II AVMs, Spetzler-Martin parameters were reported in 680: 377 were eloquent brain and 178 had deep venous drainage, totaling 555/680 (82%) high-risk SRS-treated grade II AVMs.

CONCLUSION

The literature regarding SRS for grade I-II AVM is low quality, limiting interpretation. Cautiously, we observed that SRS appears to be a safe, effective treatment for grade I-II AVM and may be considered a front-line treatment, particularly for lesions in deep or eloquent locations. Preceding publications may be influenced by selection bias, with favorable AVMs undergoing resection, whereas those at increased risk of complications and nonobliteration are disproportionately referred for SRS.