The Influence of Angioarchitectural Features on the Success of Endovascular Embolization of Cranial Dural Arteriovenous Fistulas with Onyx

Pioneering artificial intelligence-based real time assistance for intracranial liquid embolization in humans: an initial experience

BACKGROUND

Liquid embolization in neuroendovascular procedures carries the risk of embolizing an inappropriate vessel. Operators must pay close attention to multiple vessels during the procedure to avoid ischemic complications. We report our experience with real time artificial intelligence (AI) assisted liquid embolization and evaluate its performance.

METHODS

An AI-based system (Neuro-Vascular Assist, iMed technologies, Tokyo, Japan) was used in eight endovascular liquid embolization procedures in two institutions. The software automatically detects liquid embolic agent on biplane fluoroscopy images in real time and notifies operators when the agent reaches a predefined area. Safety, efficacy, and accuracy of the notifications were evaluated using recorded videos.

RESULTS

Onyx or n-butyl-2-cyanoacrylate (NBCA) was used in the treatment of arteriovenous malformation, dural arteriovenous fistula, meningioma, and chronic subdural hematoma. The mean number of true positive and false negative notifications per case was 31.8 and 2.8, respectively. No false positive notifications occurred. The precision and recall of the notifications were 100% and 92.0%, respectively. In 28.3% of the true positive notifications, the operator immediately paused agent injection after receiving the notification, which demonstrates the potential effectiveness of the AI-based system. No adverse events were associated with the notifications.

CONCLUSIONS

To the best of our knowledge, this is the first report of real time AI assistance with liquid embolization procedures in humans. The system demonstrated high notification accuracy, safety, and potential clinical usefulness in liquid embolization procedures. Further research is warranted to validate its impact on clinical outcomes. AI-based real time surgical support has the potential to advance neuroendovascular treatment.

Middle cranial fossa non-cavernous sinus dural arteriovenous fistulas: 20 years of experience

Non-cavernous sinus (CS) dural arteriovenous fistulas (DAVFs) involving the sphenoid bone are rare entities that are easily confused with one another due to the complex structure and high variability of the venous system around the middle cranial fossa. We present a large retrospective study on middle cranial fossa non-CS DAVFs and review the literature on DAVF treatment in this location as well as relative anatomy. 15 patients had DAVFs involving the lesser sphenoid wing and 11 patients had DAVFs involving the greater sphenoid wing. Six patients presented with intracranial hemorrhage or subarachnoid hemorrhage (23.1%, 6/26). The most common symptoms were eye symptoms (38.5%, 10/26). Nineteen patients were treated with trans-arterial embolization (TAE) using liquid embolic agents and two patients were treated with transvenous embolization (TVE) using Onyx or in combination with coils. Surgical disconnection of the drainage veins was performed in five patients, with three cases experiencing unsuccessful TAE. Anatomic cure was achieved in 92.3% of the patients (24/26). Twelve patients had DSA and clinical follow-up from 3 to 27 months. There was one recurrence (8.3%) of the fistula in the patient two months after the initial complete occlusion. The majority of patients can be cured endovascularly. Laterocavernous sinus DAVFs may not be embolized by transvenous approach via the cavernous sinus because there is often no connection between them in most patients. A small percentage of patients may require surgical ligation to be cured.

LIQUID - Treatment of high-grade dural arteriovenous fistulas with Squid liquid embolic agent: a prospective, observational multicenter study

BACKGROUND

Endovascular embolization is a feasible treatment for cranial dural arteriovenous fistulas (DAVFs). New embolic agents aim to improve the success of DAVF embolization.

OBJECTIVE

To assess the safety, efficacy, and short-term outcome of the treatment of DAVFs using the new liquid embolic agent Squid.

METHODS

The LIQUID study is a prospective, observational multicenter study on the treatment of high-grade (Cognard type ≥3) DAVFs with the embolic agent Squid. The primary outcome measures were safety (ie, morbidity and mortality), as well as the occlusion rate 90 to 180 days after treatment.

RESULTS

In eight centers, 53 patients (mean age 59.8 years, 22.6% female) were treated in 55 treatment sessions. Of the DAVFs, 56.6% were Cognard type III, 41.5% type IV, and 18.9% were ruptured. Squid 18 was used in 83.6% and Squid 12 in 32.7% of the treatments. The overall rate of intraprocedural or postprocedural adverse events (AEs) was 18.2%. Procedure-related AEs resulting in permanent morbidity were observed in 3.6%. One patient (1.8%) died unrelated to the procedure due to pulmonary embolism. The final complete occlusion rate at 90 to 180 days was 93.2%. After a mean follow-up of 5.5 months, the modified Rankin Scale (mRS) score was stable or improved in 93.0%. In one of the patients, worsening of the mRS score was related to the procedure (1.8%).

CONCLUSION

Squid is a safe and effective liquid embolic agent for the treatment of high-grade DAVFs.

Glue, Onyx, Squid or PHIL? Liquid Embolic Agents for the Embolization of Cerebral Arteriovenous Malformations and Dural Arteriovenous Fistulas

Background

Endovascular embolization is an effective treatment option for cerebral arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). A variety of liquid embolic agents have been and are currently used for embolization of AVMs and DAVFs. Knowledge of the special properties of the agent which is used is crucial for an effective and safe embolization procedure.

Material and Methods

This article describes the properties and indications of the liquid embolic agents which are currently available: cyanoacrylates (also called glues), and the copolymers Onyx, Squid and PHIL, as well as their respective subtypes.

Results

Cyanoacrylates were the predominantly used agents in the 1980s and 1990s. They are currently still used in specific situations, for example for the occlusion of macro-shunts, for the pressure cooker technique or in cases in which microcatheters are used that are not compatible with dimethyl-sulfoxide. The first broadly used copolymer-based embolic agent Onyx benefits from a large amount of available experience and data, which demonstrated its safety and efficacy in the treatment of cerebral vascular malformations, while its drawbacks include temporary loss of visibility during longer injections and artifacts in cross-sectional imaging. The more recently introduced agents Squid and PHIL aim to overcome these shortcomings and to improve the success rate of endovascular embolization. Novelties of these newer agents with potential advantages include extra-low viscosity versions, more stable visibility, and a lower degree of imaging artifacts.

Conclusion

All the available liquid embolic agents feature specific potential advantages and disadvantages over each other. The choice of the most appropriate embolic agent must be made based on the specific material characteristics of the agent, related to the specific anatomical characteristics of the target pathology.

The "Shiny and Thick High Heel Sign" : A novel radiologic sign for detecting intracranial dural arteriovenous fistulas with time-of-flight magnetic resonance angiography

PURPOSE

Together with the foramen ovale, the middle meningeal artery (MMA) looks like a high heel shoe print on axial time-of-flight magnetic resonance angiography (TOF-MRA) images, with the MMA resembling the heel. Cranial dural arteriovenous fistulas (DAVF) are often fed by the MMA, which can lead to an increase of signal intensity and diameter of this vessel, resulting in a more "shiny" and "thick" high heel print appearance than on the contralateral side. We describe this finding as a novel radiologic sign and provide cut-off values for the ratios of MMA signal intensities and diameters for predicting the presence of a DAVF.

METHODS

A total of 84 TOF-MRA examinations of 44 patients with DAVFs (40 with unilateral MMA feeders, 4 with bilateral feeders) and of 40 patients without DAVFs were included. Diameters and signal intensities of both MMAs were measured by two raters and evaluated using receiver operating characteristic analysis.

RESULTS

The diameters of feeding and non-feeding MMAs differed significantly, as did the ratios of signal intensities and of diameters of DAVF and control patients (P < 0.0001). Cut-off values were 1.25 for average signal intensity ratio (shiny high heel sign) and 1.21 for diameter ratio (thick high heel sign). The combination of the "shiny" and the "thick" high heel sign resulted in the highest sensitivity (92.5%) and positive predictive value (95%).

CONCLUSION

The described sign seems promising for the detection of DAVFs with noncontrast-enhanced MRI. The TOF-MRA source images should be reviewed with special attention to the MMA.

Endovascular treatment of cerebral dural arteriovenous fistulas with SQUID 12

BACKGROUND

Endovascular therapy with liquid embolic agents (LEAs) is the gold standard for the treatment of cerebral dural arteriovenous fistulas (cDAVFs). The aim of the study is to retrospectively evaluate effectiveness, safety, and midterm follow-up results of endovascular treatment of cDAVFs using SQUID 12.

METHODS

Between June 2017 and January 2020 the authors retrospectively reviewed clinical, demographic and embolization data of 19 consecutive patients with cDAVF who underwent embolization using SQUID 12. The number of arteries catheterized for each procedure, the total amount of embolic agent, the occlusion rate, the injection time, any technical and/or clinical complications were recorded. Mid-term follow-up with DSA was reviewed.

RESULTS

20 procedures were performed in 19 patients. A transarterial approach was accomplished in 19 procedure; a combined transvenous-transarterial approach was realized in 1 treatment. The average time of injection was 33 minutes (2-82 minutes), and the average amount of SQUID 12 was 2.8 mL (0.5-6 mL). Complete angiographic cure at the end of the procedure was achieved in 17 patients. No major periprocedural adverse events were recorded. Mid-term follow-up was achieved in 15 out of 19 patients and confirmed complete occlusion of the cDAVFs in 13/15 patients (87%); in 2 of the initially cured patients a small relapse was detected.

CONCLUSIONS

The treatment of the cDAVFs using SQUID 12 was effective and safe. The lower viscosity seems to allow an easier penetration of the agent with a high rate of complete occlusion of the cDAVFs.

Vascular Malformations of the Brain and Its Coverings

Vascular malformations of the brain and its coverings encompass several different vascular pathologies of the brain and its coverings, which substantially differ in morphology, clinical presentation, and prognosis, reaching from incidental, asymptomatic vascular abnormalities to life-threatening diseases with high risks of morbidity, most frequently caused by intracranial hemorrhage. In this article, the most common vascular malformations of the brain with and without arteriovenous shunting of blood (e.g., arteriovenous malformations [AVMs], dural arteriovenous fistulas [DAVFs], and cavernous malformations) are explained with a focus on definition, diagnosis, classification, and management.