Stereotactic radiosurgery of intracranial arteriovenous malformations

Prediction of Obliteration After the Gamma Knife Radiosurgery of Arteriovenous Malformations Using Hand-Crafted Radiomics and Deep-Learning Methods

INTRODUCTION

Brain arteriovenous malformations (bAVMs) are vascular abnormalities that can be treated with embolization or radiotherapy to prevent the risk of future rupture. In this study, we use hand-crafted radiomics and deep learning techniques to predict favorable vs. unfavorable outcomes following Gamma Knife radiosurgery (GKRS) of bAVMs and compare their prediction performances.

METHODS

One hundred twenty-six patients seen at one academic medical center for GKRS obliteration of bAVMs over 15 years were retrospectively reviewed. Forty-two patients met the inclusion criteria. Favorable outcomes were defined as complete nidus obliteration demonstrated on cerebral angiogram and asymptomatic recovery. Unfavorable outcomes were defined as incomplete obliteration or complications relating to the AVM that developed after GKRS. Outcome predictions were made using a random forest model with hand-crafted radiomic features and a fine-tuned ResNet-34 convolutional neural network (CNN) model. The performance was evaluated by using a ten-fold cross-validation technique.

RESULTS

The average accuracy and area-under-curve (AUC) values of the Random Forest Classifier (RFC) with radiomics features were 68.5 ±9.80% and 0.705 ±0.086, whereas those of the ResNet-34 model were 60.0 ±11.9% and 0.694 ±0.124. Four radiomics features used with RFC discriminated unfavorable response cases from favorable response cases with statistical significance. When cropped images were used with ResNet-34, the accuracy and AUC decreased to 59.3 ± 14.2% and 55.4 ±10.4%, respectively.

CONCLUSIONS

A hand-crafted radiomics model and a pre-trained CNN model can be fine-tuned on pre-treatment MRI scans to predict clinical outcomes of AVM patients undergoing GKRS with equivalent prediction performance. The outcome predictions are promising but require further external validation on more patients.

Current perspectives and trends in the treatment of brain arteriovenous malformations: a review and bibliometric analysis

Background

Currently, there is a lack of intuitive analysis regarding the development trend, main authors, and research hotspots in the field of cerebral arteriovenous malformation treatment, as well as a detailed elaboration of possible research hotspots.

Methods

A bibliometric analysis was conducted on data retrieved from the Web of Science core collection database between 2000 and 2022. The analysis was performed using R, VOSviewer, CiteSpace software, and an online bibliometric platform.

Results

A total of 1,356 articles were collected, and the number of publications has increased over time. The United States and the University of Pittsburgh are the most prolific countries and institutions in the field. The top three cited authors are Kondziolka D, Sheehan JP, and Lunsford LD. The Journal of Neurosurgery and Neurosurgery are two of the most influential journals in the field of brain arteriovenous malformation treatment research, with higher H-index, total citations, and number of publications. Furthermore, the analysis of keywords indicates that "aruba trial," "randomised trial," "microsurgery," "onyx embolization," and "Spetzler-Martin grade" may become research focal points. Additionally, this paper discusses the current research status, existing issues, and potential future research directions for the treatment of brain arteriovenous malformations.

Conclusion

This bibliometric study comprehensively analyses the publication trend of cerebral arteriovenous malformation treatment in the past 20 years. It covers the trend of international cooperation, publications, and research hotspots. This information provides an important reference for scholars to further study cerebral arteriovenous malformation.

Chronic Encapsulated Expanding Hematomas After Stereotactic Radiosurgery for Intracranial Arteriovenous Malformations: An International Multicenter Case Series

BACKGROUND

Stereotactic radiosurgery (SRS) offers a minimally invasive treatment modality for appropriately selected intracranial arteriovenous malformations (AVMs). Recent reports have described the development of rare, delayed chronic encapsulated expanding hematomas (CEEHs) at the site of an angiographically confirmed obliterated AVM.

OBJECTIVE

To elucidate the incidence, characteristics, and management of CEEH in patients with AVM after SRS.

METHODS

The records of all patients who underwent SRS for an intracranial AVM at 4 institutions participating in the International Radiosurgery Research Foundation between 1987 and 2021 were retrospectively reviewed. Data regarding characteristics of the AVM, SRS treatment parameters, CEEH presentation, management, and outcomes were collected and analyzed.

RESULTS

Among 5430 patients, 15 developed a CEEH at a crude incidence of 0.28%. Nine patients were female, and the mean age was 43 ± 14.6 years. Nine patients underwent surgical evacuation, while 6 were managed conservatively. The median CEEH development latency was 106 months after SRS. The patients were followed for a median of 32 months, and 9 patients improved clinically, while 6 patients remained stable. No intraoperative complications were reported after CEEH resection, although 1 patient recovered from postoperative meningitis requiring intravenous antibiotics.

CONCLUSION

CEEH is a rare, late complication of AVM SRS with an incidence of 0.28% and a median latency of 106 months. In the presence of a delayed and symptomatic expanding hematoma in the bed of an angiographically obliterated AVM, surgical resection resulted in clinical improvement in most patients. Conservative management is possible in asymptomatic patients with stable, small-sized hematomas in deeply seated locations.

Peri-procedure efficacy and safety of one-stop hybrid surgery for the treatment of brain arteriovenous malformations: A single-center preliminary experience

Background

Some deficiencies and shortcomings in treatment strategies of brain arteriovenous malformation (bAVM) remain. It is worth exploring whether the one-stop hybrid surgical platform can play a positive role in the treatment of bAVM.

Objective

This study investigated short clinical and angiographic results of one-stop hybrid surgery for the treatment of bAVM.

Methods

All patients with bAVM treated with one-stop hybrid surgery were reviewed from February 2017 to December 2021. Data including demographic information, clinical conditions, characteristics of AVM, procedure details, and clinical and angiographic results were collected.

Result

In total, 150 cerebral bAVM patients received one-stop hybrid surgery; among them, 122 received surgical resection assisted by intraoperative DSA, and 28 were treated with combination surgical resection and endovascular embolization. Complete angiographic obliteration of the AVM was achieved in 136 patients (90.7%), and procedure-related death and neurological deficit rates were 7.3%. Of all relevant variables, logistic regression analysis showed that the Spetzler & Martin (S&M) score was the only factor related to the cure rate (P < 0.001) and endpoint complication rate (P = 0.007).

Conclusions

In our preliminary experience, one-stop hybrid surgery for the treatment of brain AVMs achieves a high angiographic total occlusion rate, with acceptable peri-procedure morbidity and mortality. For S&M 4 and 5 lesions, more cases and further study are needed to investigate the effects and safety of hybrid surgery.

The addition of adjuvant radiotherapy in the management of extracranial arterio-venous malformations: a case discussion

Introduction:

The management of extracranial arterio-venous malformations (AVMs) is complex and often requires a multidisciplinary approach. Currently, treatment includes surgical resection and embolotherapy.

Methods:

We present the case of a foot AVM that was managed with adjuvant radiotherapy after previous surgery and embolotherapy had been attempted, and we discuss the role of radiotherapy in the management of extracranial AVMs.

Results:

The malformation was successfully eradicated with complete obliteration of the nidus and no recurrence.

Conclusions:

The addition of radiotherapy in the management of extracranial arterio-venous malformations offers promising results using similar doses to those used in brain AVMs.

Combined Microsurgery and Endovascular Intervention in One-Stop for Treatment of Cerebral Arteriovenous Malformation: The Efficacy of a Hybrid Operation

To investigate the efficacy of a hybrid operation combining microsurgical resection and endovascular interventions in a one-stop treatment of cerebral arteriovenous malformation (AVM). Patients were divided into two groups: patients who received a hybrid operation, and patients receiving a non-hybrid operation. The hybrid operation group consisted of microsurgical resection with intraoperative angiography, or endovascular embolization. The non-hybrid operation group consisted of microsurgical resection or endovascular embolization, or microsurgery combined with embolization in multiple steps. Comprehensive clinical data was collected for all patients, including preoperative Glasgow Coma Scale score, Spetzler-Martin grade, rehemorrhagia, image follow-up, and 6-month outcomes of the modified Rankin Scale (mRS) score. This study included 22 cases in the hybrid operation group. The remnants were noted on intraoperative angiography in the four patients that were resected within the same session. The non-hybrid group consisted of 52 patients. There were no statistical differences between the two groups with GCS and Spetzler-Martin grade score. The mortality rate in the hybrid operation group was 4.5%, which was lower than the 7.6% obtained in the control group. No patients experienced post-operation rehemorrhagia in the hybrid operation group, but five cases occurred in the control group. The follow-up radiological cure rates were 100% in the hybrid group and 65.9% in the control group. The rate of good outcome was 81.8% in the hybrid operation group and 69.2% in the control group, although there was no significant difference. The hybrid operation is a safe and efficacious strategy for treating cerebral AVMs.

Optimizing contrast-enhanced cone-beam CT protocol to facilitate simultaneous visualization of neurovascular pathologies and surrounding structures of interest

OBJECTIVE

Contrast-enhanced cone-beam computed tomography (CBCT) imaging is commonly used for evaluating neurovascular stents and their relationship to the parent artery or vascular pathologies such as arteriovenous malformations (AVMs) and dural arteriovenous fistulas (dAVFs) in the context of surrounding anatomical structures. The purpose of this study was to understand the effects of varying concentrations of contrast medium used in CBCT imaging for optimal visualization of various endovascular devices and anatomical pathologies.

METHODS

Thirty-five patients with various neurovascular pathologies were included in the study. Contrast-enhanced CBCT images (20 s DR, Siemens syngo DynaCT, Siemens AG, Forchheim, Germany) were acquired in all cases, with varying dilutions of contrast medium, from 1% to 30%. The injection rate was kept constant at 3 cc/sec with an X-ray delay of two sec, and a total volume of 66 cc of diluted contrast was administered. Results from visual and quantitative analysis were reported.

RESULTS

Ten percent dilution of contrast medium resulted in the best image differentiation between flow-diverter devices and the parent artery. Concentrations as low as 2.5% contrast medium also resulted in identifying AVMs in the context of the surrounding brain parenchyma, whereas 20% to 30% dilution provided the best visualization of residual AVMs with prior Onyx embolization and dAVFs in the presence of bony structures.

CONCLUSIONS

Simultaneous visualization of brain parenchyma, bony structures, devices, and pathological anatomy using contrast-enhanced CBCT imaging is feasible with appropriate doses of iodinated contrast, and should be tailored to the individual case based on the goals of CBCT.

Repeat Radiosurgery Treatment After Cavernous Malformation Radiosurgery

OBJECTIVE

Of cavernous malformations (CMs) treated with radiosurgery (RS), 5% bleed after 2-year initial latency period. This rate is similar to failure rate of RS for other pathologies, which often require repeat RS for favorable outcome. The aim of this pilot study was to define failure of CM RS and to assess safety of second RS.

METHODS

Retrospective analysis was performed of 7 of 345 CMs retreated with RS; 6 CMs were deep-seated, and 1 was superficial. Median time between the 2 treatments was 8 years (range, 3-16 years), and median follow-up time after second RS was 3 years (range, 1-9 years).

RESULTS

Following the 2-year latency period after RS, 6% of deep-seated and 5% of hemispheric CMs, and 6% of deep-seated and 2% of hemispheric lesions caused transient neurologic deficits without hemorrhage. A second treatment was indicated for rebleed in 5 cases and for recurrent transient neurologic deficits in 2 cases. Prescribed dose was 15 Gy (range, 12-20 Gy) at first treatment and 12 Gy (range, 12-18 Gy) at second treatment. Target volumes were 692 mm³ (range, 54-2400 mm³) and 935 mm³ (range, 150-1550 mm³) at first and second treatments, respectively, and treatment volumes were 811 mm³ (range, 79-2500 mm³) and 962 mm³ (range, 194-1750 mm³), respectively. Differences in treatment parameters were not significant. Reason for failure was inaccurate target definition in only 2 cases. There were no bleeds, morbidity, or mortality after second RS.

CONCLUSIONS

Second RS applied to previously treated CMs is safe and may be effective. Further investigations are needed to verify these findings and assess long-term benefit of second RS.

Stable thrombus formation on irradiated microvascular endothelial cells under pulsatile flow: Pre-testing annexin V-thrombin conjugate for treatment of brain arteriovenous malformations

BACKGROUND

Our goal is to develop a vascular targeting treatment for brain arteriovenous malformations (AVMs). Externalized phosphatidylserine has been established as a potential biomarker on the endothelium of irradiated AVM blood vessels. We hypothesize that phosphatidylserine could be selectively targeted after AVM radiosurgery with a ligand-directed vascular targeting agent to achieve localized thrombosis and rapid occlusion of pathological AVM vessels.

OBJECTIVE

The study aim was to establish an in vitro parallel-plate flow chamber to test the efficacy of a pro-thrombotic conjugate targeting phosphatidylserine.

METHODS

Conjugate was prepared by Lys-Lys cross-linking of thrombin with the phosphatidylserine-targeting ligand, annexin V. Cerebral microvascular endothelial cells were irradiated (5, 15, and 25 Gy) and after 1 or 3 days assembled in a parallel-plate flow chamber containing whole human blood and conjugate (1.25 or 2.5 μg/mL). Confocal microscopy was used to assess thrombus formation after flow via binding and aggregation of fluorescently-labelled platelets and fibrinogen.

RESULTS AND CONCLUSIONS

The annexin V-thrombin conjugate induced rapid thrombosis (fibrin deposition) on irradiated endothelial cells under shear stress in the parallel-plate flow device. Unconjugated, non-targeting thrombin did not induce fibrin deposition. A synergistic interaction between radiation and conjugate dose was observed. Thrombosis was greatest at the highest combined doses of radiation (25 Gy) and conjugate (2.5 μg/mL). The parallel-plate flow system provides a rapid method to pre-test pro-thrombotic vascular targeting agents. These findings validate the translation of the annexin V-thrombin conjugate to pre-clinical studies.

Dynamic conformal arc radiosurgery for arteriovenous malformations: Outcome and influence of clinical and dosimetrical data

PURPOSE

To assess efficacy, toxicity, and their predictive factors for dynamic conformal arc arteriovenous malformations (AVM) stereotactic radiosurgery.

METHOD

Data concerning 90 consecutive patients were retrospectively studied. Clinical, radiological, dosimetrical data and quality indexes were computed.

RESULTS

AVM median volume was 1.06cc. Median prescribed dose was 22Gy. Total occlusion was obtained for 69% of patients. Post-radiosurgery annual hemorrhage rate was 2.2%. Predictive factor for total occlusion was delivered dose. Undesirable events occurred for 28% of patients. Predictive factors for adverse events were AVM revealing mode with seizure or headache, age≤28, AVM diameter≥3cm Spetzler-Martin score≥4, V12Gy≥2cc, large target volume and low homogeneity index (p<0.05). Brain parenchymal radiological reactions concerned 23% of patients, and their predictive factors were AVM revelation by seizure, deep localization, AVM diameter≥3cm, Spetzler-Martin score≥4, previous radiosurgery, numerous embolization, target volume, V12Gy and low homogeneity index (p<0.05).

CONCLUSION

Occlusion rate and toxicities are comparable to other series. Specific attention must be paid on pre-treatment clinical data, and target volume should be as small as possible, without reducing the delivered dose.

Therapeutic management of cerebral arteriovenous malformations: a review

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

Pathological Evaluation of Radiation-Induced Vascular Lesions of the Brain: Distinct from De Novo Cavernous Hemangioma

PURPOSE

We aimed to evaluate the histologic and radiologic findings of vascular lesions after stereotactic radiosurgery (SRS) categorized as radiation-induced cavernous hemangioma (RICH).

MATERIALS AND METHODS

Among 89 patients who underwent neurosurgery for cavernous hemangioma, eight RICHs from 7 patients and 10 de novo CHs from 10 patients were selected for histopathological and radiological comparison.

RESULTS

Histologically, RICHs showed hematoma-like gross appearance. Microscopically, RICH exhibited a hematoma-like area accompanied by proliferation of thin-walled vasculature with fibrin deposits and infiltrating foamy macrophages. In contrast, CHs demonstrated localized malformed vasculature containing fresh and old clotted blood on gross examination. Typically, CHs consisted of thick, ectatic hyalinized vessels lined by endothelium under a light microscope. Magnetic resonance imaging of RICHs revealed some overlapping but distinct features with CHs, including enhancing cystic and solid components with absence or incomplete popcorn-like appearance and partial hemosiderin rims.

CONCLUSION

Together with histologic and radiologic findings, RICH may result from blood-filled space after tissue destruction by SRS, accompanied with radiation-induced reactive changes rather than vascular malformation. Thus, the term "RICH" would be inappropriate, because it is more likely to be an inactive organizing hematoma rather than proliferation of malformed vasculature.

Experimental Animal Models of Arteriovenous Malformation: A Review

Arteriovenous malformations (AVMs) are congenital lesions that cause brain haemorrhage in children and young adults. Current treatment modalities include surgery, radiosurgery and embolization. These treatments are generally effective only for small AVMs. Over one third of AVMs cannot be treated safely and effectively with existing options. Several animal models have been developed with the aims of understanding AVM pathophysiology and improving treatment. No animal model perfectly mimics a human AVM. Each model has limitations and advantages. Models contribute to the understanding of AVMs and hopefully to the development of improved therapies. This paper reviews animal models of AVMs and their advantages and disadvantages.

Deletion of Rbpj from postnatal endothelium leads to abnormal arteriovenous shunting in mice

Arteriovenous malformations (AVMs) are tortuous vessels characterized by arteriovenous (AV) shunts, which displace capillaries and shunt blood directly from artery to vein. Notch signaling regulates embryonic AV specification by promoting arterial, as opposed to venous, endothelial cell (EC) fate. To understand the essential role of endothelial Notch signaling in postnatal AV organization, we used inducible Cre-loxP recombination to delete Rbpj, a mediator of canonical Notch signaling, from postnatal ECs in mice. Deletion of endothelial Rbpj from birth resulted in features of AVMs by P14, including abnormal AV shunting and tortuous vessels in the brain, intestine and heart. We further analyzed brain AVMs, as they pose particular health risks. Consistent with AVM pathology, we found cerebral hemorrhage, hypoxia and necrosis, and neurological deficits. AV shunts originated from capillaries (and possibly venules), with the earliest detectable morphological abnormalities in AV connections by P8. Prior to AV shunt formation, alterations in EC gene expression were detected, including decreased Efnb2 and increased Pai1, which encodes a downstream effector of TGFβ signaling. After AV shunts had formed, whole-mount immunostaining showed decreased Efnb2 and increased Ephb4 expression within AV shunts, suggesting that ECs were reprogrammed from arterial to venous identity. Deletion of Rbpj from adult ECs led to tortuosities in gastrointestinal, uterine and skin vascular beds, but had mild effects in the brain. Our results demonstrate a temporal requirement for Rbpj in postnatal ECs to maintain proper artery, capillary and vein organization and to prevent abnormal AV shunting and AVM pathogenesis.