Contemporary Imaging of Cerebral Arteriovenous Malformations

Cerebrovascular morphology: Insights into normal variations, aging effects, and disease implications

Cerebrovascular morphology plays a critical role in brain health, influencing cerebral blood flow (CBF) and contributing to the pathogenesis of various neurological diseases. This review examines the anatomical structure of the cerebrovascular network and its variations in healthy and diseased populations and highlights age-related changes and their implications in various neurological conditions. Normal variations, including the completeness and anatomical anomalies of the Circle of Willis and collateral circulation, are discussed in relation to their impact on CBF and susceptibility to ischemic events. Age-related changes in the cerebrovascular system, such as alterations in vessel geometry and density, are explored for their contributions to age-related neurological disorders, including Alzheimer's disease and vascular dementia. Advances in medical imaging and computational methods have enabled automatic quantitative assessment of cerebrovascular structures, facilitating the identification of pathological changes in both acute and chronic cerebrovascular disorders. Emerging technologies, including machine learning and computational fluid dynamics, offer new tools for predicting disease risk and patient outcomes based on vascular morphology. This review underscores the importance of understanding cerebrovascular remodeling for early diagnosis and the development of novel therapeutic approaches in brain diseases.

MR perfusion source mapping depicts venous territories and reveals perfusion modulation during neural activation

The cerebral venous system plays a crucial role in neurological and vascular conditions, yet its hemodynamics remain underexplored due to its complexity and variability across individuals. To address this, we develop a venous perfusion source mapping method using Displacement Spectrum MRI, a non-contrast technique that leverages blood water as an endogenous tracer. Our technique encodes spatial information into the magnetization of blood water spins during tagging and detects it once the tagged blood reaches the brain's surface, where the signal-to-noise ratio is 3-4 times higher. We resolve the sources of blood entering the imaging slice across short (10 ms) to long (3 s) evolution times, effectively capturing perfusion sources in reverse. This approach enables the measurement of slow venous blood flow, including potential contributions from capillary beds and surrounding tissue. We demonstrate perfusion source mapping in the superior cerebral veins, verify its sensitivity to global perfusion modulation induced by caffeine, and establish its specificity by showing repeatable local perfusion modulation during neural activation. From all blood within the imaging slice, our method localizes the portion originating from an activated region upstream.

Pial arteriovenous fistula with a large intraparenchymal hemorrhage in a 9-year-old child: a case report and case-based mini review

BACKGROUND

Pial arteriovenous fistulas are rare cerebrovascular malformations, predominantly occurring in the pediatric population. The spectrum of symptoms is broad, ranging from incidental findings to intracranial hemorrhage. However, accurate diagnosis and optimal treatment require, among other factors, dynamic imaging modalities and interdisciplinary management.

CASE PRESENTATION

We describe a case of a 9-year-old patient presenting with acute spontaneous headache and apathy. MRI revealed a right temporal intraparenchymal hemorrhage, without signs of an underlying vascular pathology. Cerebral angiography was performed, revealing a suspected pial arteriovenous fistula. The patient was scheduled for surgical hematoma removal and resection of the pial fistula, with intraoperative angiographic control. After hematoma removal and resection of the pial fistula, intraoperative cerebral angiography revealed an additional fistula point that had not been appreciated on the initial preoperative angiography. The craniotomy was extended and the remaining fistula was resected. Final intraoperative angiography confirmed complete resection of the pial fistula.

CONCLUSION

Pediatric pial arteriovenous fistulas are rare, complex, and challenging arteriovenous lesions. Accurate diagnosis and an interdisciplinary management are essential. However, consensus on the diagnostic workflow and treatment approach remains lacking. Therefore, we report our case and propose a diagnostic and therapeutic workup for ruptured vascular intracranial anomalies in children.

Wyburn-Mason disease: Management of a Spetzler-Martin grade 5 arteriovenous malformation with predominant thalamic involvement

Wyburn-Mason disease (WMD) is a rare congenital phakomatosis known for its complex arteriovenous malformations (AVMs) predominantly affecting the brain and ocular structures. We present the case of a 19-year-old female with an unruptured Spetzler-Martin grade 5 left thalamic AVM, who initially exhibited progressive visual impairment and migraines. Following diagnosis, she was treated with trametinib, a MEK inhibitor; however, nine months later, she developed acute complications, including left monocular blindness and right hemisensory loss. Imaging revealed narrowing of the left internal carotid artery and ischemia, leading to the discontinuation of trametinib. Her condition stabilized with gabapentin and supportive therapies. This case emphasizes the potential therapeutic role and risks of MEK inhibitors in managing high-grade AVMs in WMD and highlights the need for individualized management and careful monitoring in such cases.

Machine learning based classification of spontaneous intracranial hemorrhages using radiomics features

PURPOSE

To assess the efficacy of radiomics features extracted from non-contrast computed tomography (NCCT) scans in differentiating multiple etiologies of spontaneous intracerebral hemorrhage (ICH).

METHODS

CT images and clinical data from 141 ICH patients from 2010 to 2022 were collected. The cohort comprised primary (n = 57), tumorous (n = 46), and vascular malformation-related ICH (n = 38). Radiomics features were extracted from the initial brain NCCT scans and identified potential features using mutual information. A hierarchical classification with AdaBoost classifiers was employed to classify the multiple etiologies of ICH. Age of the patient and ICH's location were examined alongside radiomics features. The accuracy, area under the curve (AUC), sensitivity, and specificity were used to evaluate classification performance.

RESULTS

The proposed method achieved an accuracy of 0.79. For identifying primary ICH, the model achieved a sensitivity of 0.86 and specificity of 0.87. Meanwhile, the sensitivity and specificity for identifying tumoral causes were 0.78 and 0.93, respectively. For vascular malformation, the model reached a sensitivity and specificity of 0.72 and 0.89, respectively. The AUCs for primary, tumorous, and vascular malformation were 0.86, 0.85, and 0.82, respectively. The findings further highlight the importance of texture-based variables in ICH classification. The age and location of the ICH can enhance the classification performance.

CONCLUSION

The use of a machine learning model with radiomics features has the potential in classifying the three types of non-traumatic ICH. It may help the radiologist decide on an appropriate further examination plan to arrive at a correct diagnosis.

Long-term outcomes and prognostic factors after surgery alone for brain arteriovenous malformation

OBJECTIVES

There is a paucity of data regarding the long-term hemorrhage/progression outcomes of brain arteriovenous malformation (BAVM). The purpose of this study was to examine the outcomes of surgical treatment alone over a long follow-up period.

MATERIALS AND METHODS

All patients (n = 356) harboring Grade I-III BAVMs who had been surgically treated alone between January 2010 and December 2019 were included. Univariate analysis and multivariate analysis with proportional hazard models were implemented to identify the predictors of hemorrhage-free survival (HFS) (n = 356) and progression-free survival (PFS) (n = 334).

RESULTS

Of the 356 BAVM patients, 233 were male and 123 were female (male-to-female ratio of 1.89:1). Rehemorrhage was observed in 22 (6.2%) patients. The overall HFS rates at 5, 10, and 15 years in the entire cohort were 96.0%, 92.4%, and 91.1%, respectively. A 1 cm3 increase in lesion volume (hazard ratio [HR] = 1.049, 95% confidence interval [CI] = 1.013-1.085; P = 0.007) was a significant adverse factor for HFS. The probabilities of PFS at 5, 10, and 15 years were 94.9%, 90.6%, and 85.5%, respectively. With respect to clinical predictors of PFS, only male sex (HR = 3.146, 95% CI = 1.088-9.098; P = 0.034) was a significant predictor of PFS after surgical treatment in the univariate analysis.

CONCLUSIONS

For the majority of patients, surgery remains the first-line treatment for BAVMs. Our study included a significant subset of patients who were successfully managed by surgery alone.

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.

Prevalence of Retinal Venous Malformations in Patients With Cerebral Cavernous or Arteriovenous Malformations

BACKGROUND

Cerebral vascular malformations (CVMs) may result in hemorrhage, seizure, neurologic dysfunction, and death. CVMs include capillary telangiectasias, venous malformations, cavernous malformations, and arteriovenous malformations. Cavernous and arteriovenous malformations carry the highest risk of complications. Retinal venous malformations (RVMs) have been proposed as an associated finding. Our objective was to determine the prevalence of RVMs in patients with high-risk CVMs.

METHODS

We retrospectively reviewed patients diagnosed with cerebral cavernous or arteriovenous malformations (high-risk CVMs) who were evaluated by the ophthalmology service at Northwestern University between 2017 and 2020. Patients were stratified into 3 cohorts based on level of certainty: dilated funduscopic examination (DFE), DFE with any form of ocular imaging, and DFE with complete imaging of the macula. We recorded ophthalmic examination abnormalities, ocular imaging findings, and major CVM complications.

RESULTS

We evaluated 156 patients with high-risk CVMs who had undergone DFE. Ocular imaging of any type was performed in 56 patients, of whom 46 had complete imaging of the macula. Zero RVMs were identified in any cohort (95% confidence interval: 0%-1.9% for the entire cohort, 0%-5.4% for any ocular imaging cohort, and 0%-6.5% for the complete macular imaging cohort). Cerebral hemorrhage or seizure occurred in 15%-33% of patients. Associated visual field defects or cranial nerve palsies were found in 14%-20% of patients.

CONCLUSIONS

Zero RVMs were identified in patients with high-risk CVMs. However, neuro-ophthalmic findings were common. Therefore, we recommend neuroimaging for patients with RVMs and neuro-ophthalmic signs or symptoms. In asymptomatic patients with RVMs, a potential algorithm for neuroimaging is proposed.

Imaging of supratentorial intraventricular masses in children:a pictorial review- part 1

PURPOSE

This article is the first in a two-part series designed to provide a comprehensive overview of the range of supratentorial intraventricular masses observed in children. Our primary objective is to discuss the diverse types of intraventricular masses that originate not only from cells within the choroid plexus but also from other sources.

METHODS

In this article, we review relevant epidemiological data, the current genetics/molecular classification as outlined in the fifth edition of the World Health Organization's Classification of tumours of the Central Nervous System and noteworthy imaging findings. We conduct an exhaustive analysis of primary choroid plexus tumours as well as other conditions such as choroid plexus hyperplasia, choroid plexus cyst, choroid plexus xanthogranuloma, atypical teratoid rhabdoid tumour, meningioma, arteriovenous malformation and metastasis.

RESULTS

We comprehensively evaluated each supratentorial intraventricular mass, providing an in-depth analysis of their unique clinical and histological characteristics. The fifth edition of the World Health Organization Classification of Tumours of the Central Nervous System introduces major modifications. These important changes could potentially have a profound impact on the management strategies and subsequent outcomes of these tumours.

CONCLUSION

Intraventricular masses in children can arise from various sources. Surgical intervention is key for certain supratentorial intraventricular masses in paediatric patients, with preoperative neuroimaging essential to decide the best treatment approach, surgical or otherwise, as some cases may not require surgery.

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.

Fetal choroid plexus arteriovenous malformation, masquerading as a neoplastic lesion

A woman in her 20s, who was pregnant, underwent a routine antenatal ultrasound revealing organised intraventricular haemorrhage and a vascular area in the left thalamic region. Fetal MRI raised suspicion of arteriovenous malformation (AVM). The baby was delivered at 36 weeks via C-section, and initial brain MRI suggested a possible neoplastic lesion.Cerebral angiography confirmed a large AVM involving the left choroid plexus with arterial feeders from the left anterior and posterior choroidal arteries and a large venous varix draining into the vein of Galen. Both arterial feeders were successfully embolised with Onyx and glue, achieving complete occlusion.Choroid plexus AVMs are rare and often lead to intraventricular or intraparenchymal haemorrhage. Surgical treatment has shown success, but endovascular management is effective, especially for small, deep-seated AVMs, offering a better prognosis.

Value of contrast-enhanced MR angiography for the follow-up of treated brain arteriovenous malformations: systematic review and meta-analysis

OBJECTIVE

To estimate the diagnostic value of contrast-enhanced MR angiography (CE-MRA) in identifying residual brain arteriovenous malformations (AVMs) after treatment.

METHODS

We retrieved appropriate references from the electronic databases of PubMed, Web of Science, Embase, and Cochrane Library, and then evaluated the methodology quality of included references using the QUADAS-2 tool. We calculated the pooled sensitivity and specificity by applying a bivariate mixed-effects model and detected the publication bias using Deeks' funnel plot. The values of I2 were used to test heterogeneity and meta-regression analyses were performed to search for the causes of heterogeneity.

RESULTS

We included 7 eligible studies containing 223 participants. Compared with a gold standard, the overall sensitivity and specificity of CE-MRA in detecting residual brain AVMs were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00), respectively. Based on the summary ROC curve, the AUC was 0.89 (95% CI 0.86-0.92). Heterogeneity could be observed in our study, especially for the specificity (I2 = 74.23%). Furthermore, there was no evidence of publication bias.

CONCLUSIONS

Our study provides evidence that CE-MRA has good diagnostic value and specificity for the follow-up of treated brain AVMs. Nevertheless, considering the small sample size, heterogeneity, and many factors that may affect the diagnostic accuracy, future large-sample, prospective studies are necessary to validate the results.

KEY POINTS

• The pooled sensitivity and specificity of contrast-enhanced MR angiography (CE-MRA) in detecting residual arteriovenous malformations (AVMs) were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00). • The four-dimensional CE-MRA showed less sensitivity than the three-dimensional CE-MRA for treated AVMs. • CE-MRA is helpful to identify residual AVMs and reduce excessive DSA during follow-up.

Pial arteriovenous fistula associated with vein of Galen dilatation in adult: A case report and MRI findings

Pial arteriovenous fistula (PAVF) is a rare intracranial vascular lesion where direct communication exists between one or more pial arteries and a cerebral vein, without an intervening nidus and located in the subpial meningeal space. When the drainage of PAVF involves a dilated, but already formed vein of Galen (VOG), it should be distinguished from other vascular lesions located in this area, because their angio-architecture, natural history and treatment options are different. A 33-year-old female was admitted to our hospital with a history of new-onset generalized tonic-clonic seizures. Clinical examination showed no neurological deficit. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) depicted an arteriovenous fistula that was fed by the pial branches from left posterior cerebral artery and drained into the medial atrial vein before joining the VOG confluence and causing VOG dilatation. No nidus between the feeding arteries and draining vein, dural feeding arteries, or anatomical variations commonly seen with true vein of Galen aneurysmal malformations (VOGM) were found. These finding suggested a diagnosis of a PAVF associated with vein of Galen dilatation, which was confirmed by digital subtraction angiography. The patient was treated with transarterial glue embolization in 1 section, resulting in nearly complete occlusion of the fistula. Conventional MRI and MRA are noninvasive modalities that can provide valuable information regarding the anatomic localization of the fistula point, the feeding arteries, the venous sac, and their relationship with surrounding structures. These techniques are helpful for accurate diagnosis and treatment planning.

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.

Non-Angry Superficial Draining Veins: A New Technique in Identifying the Extent of Nidus Excision during Cerebral Arteriovenous Malformation Surgery

BACKGROUND

As essential techniques, intraoperative indocyanine green video angiography (ICG-VA) and FLOW 800 have been widely used in microsurgery for arteriovenous malformations (AVMs). In the present report, we introduced a supplementary technical trick for judging the degree of lesion resection when there were superficial drainage veins. FLOW 800 analysis is used to verify our conjecture.

METHODS

A retrospective analysis of a 33 case cohort treated surgically from June 2020 to September 2022 was conducted and their lesions were removed by superficial drainage veins as a supplementary technical trick and analyzed with FLOW800.

RESULTS

In our 33 AVMs, the feeding artery was visualized earlier than the draining vein. Intraoperatively, the T1/2 peak and slope of the draining vein were significantly higher than that of the lesion. However, the maximum fluorescence intensity (MFI) of the draining vein decreased as the procedure progressed (p < 0.001). After reducing the blood flow to the nidus by progressive dissection of the feeding artery, the arteriovenous transit time (AVTT) decreased from 0.64 ± 0.47 s, was prolonged to 2.38 ± 0.52 (p < 0.001), and the MFI and slope of the nidus decreased from the pre-resection 435.42 ± 43.90 AI and 139.77 ± 27.55 AI/s, and decreased to 386.70 ± 48.17 AI and 116.12 ± 17.46 AI/s (p < 0.001). After resection of the nidus, the T1/2 peak of the draining vein increased from 21.42 ± 4.70 s, prolonged to after dissection of the blood feeding artery, 23.07 ± 5.29 s (p = 0.424), and after resection of the lesion, 25.13 ± 5.46 s (p = 0.016), with a slope from 135.79 ± 28.17 AI/s increased to 210.86 ± 59.67 AI/s (p < 0.001).

CONCLUSIONS

ICG-VA integrated with FLOW 800 is an available method for determining the velocity of superficial drainage veins. Whether the color of the superficial drainage veins on the cortical surface returns to normal can determine whether the lesion is completely resected and can reduce the possibility of residual postoperative lesions.

Photon Counting CT Angiography of the Head and Neck: Image Quality Assessment of Polyenergetic and Virtual Monoenergetic Reconstructions

Background: The purpose of the present study was the evaluation of the image quality of polyenergetic and monoenergetic reconstructions (PERs and MERs) of CT angiographies (CTAs) of the head and neck acquired with the novel photon counting CT (PCCT) method in clinical routine. Methods: Thirty-seven patients were enrolled in this retrospective study. Quantitative image parameters of the extracranial, intracranial and cerebral arteries were evaluated for the PER and MER (40–120 keV). Additionally, two radiologists rated the perceived image quality. Results: The mean CTDI_vol used in the PCCT was 8.31 ± 1.19 mGy. The highest signal within the vessels was detected in the 40 keV MER, whereas the lowest noise was detected in the 115 keV MER. The most favorable contrast-to-noise-ratio (CNR) and signal-to-noise-ratio (SNR) were detected in the PER and low keV MER. In the qualitative image analysis, the PER was superior to the MER in all rated criteria. For MER, 60–65 keV was rated as best image quality. Conclusion: Overall, PCCT offers excellent image quality for CTAs of the head and neck. At the current state, the PER of the PCCT seems to be the most favorable reconstruction for diagnostic reporting.

Anomalous location of intracranial vessels in adults

Anomalous intracranial vessels are not uncommon, and this finding is not always associated with arteriovenous malformations. Other conditions such as anomalous connections between arteries or phlebitc patterns can also present as vessels with abnormal intracranial locations. Noninvasive diagnosis is important to determine whether to do more invasive tests such as cerebral digital subtraction angiography or to estimate the risk of bleeding in arteriovenous malformations and therefore to evaluate the need for endovascular/surgical treatment. In this paper, we present an algorithm for the differential diagnosis of anomalous intracranial vessels according to their location (intra/extra-axial) and function (whether the vessels are arterialized). Moreover, we analyze the important points of the angioarchitecture of the principal arteriovenous malformations with risk of intracranial bleeding, such as pial arteriovenous malformations and dural fistulas.

First Experience in the Control of the Venous Side of the Brain AVM

Background and purpose: Brain arteriovenous malformations (AVM) are increasingly curable with endovascular embolization. This study examines the preliminary experience with a novel double-sided hybrid approach in the treatment of cerebral arteriovenous malformations (AVM) versus a purely single-sided intra-arterial approach. Materials and methods: The single-center study cohort included 18 patients with brain AVMs (Spetzler–Martin Grade 2 or 3) having stand-alone endovascular treatment with either the arterial-side-only pressure cooker technique (aPCT) (group 1; n = 9) or a double-sided hybrid intra-arterial and transvenous approach (HIPRENE) (group 2; n = 9). Results: Patients belonging to group 2 had lower rates of intra-procedural hemorrhaging (66.7% vs. 33.3%, p = 0.169) and needed fewer treatment sessions to achieve nidus occlusion (1.7 vs. 1.2, p = 0.136). The HIPRENE treatment regime led to higher nidus occlusion rates after the initial treatment compared to aPCT (77.7% vs. 44.4%, p = 0.167). Group 2 patients had a lower rate of neuromonitoring events (22.2% vs. 44.4%, p = 0.310) and fewer accounts of blood flow obstruction in post-operative MRIs (33.3% vs. 55.6%, p = 0.319). Conclusion: A double-sided hybrid intra-arterial and transvenous approach might have benefits for curative endovascular brain AVM treatment in patients with Spetzler–Martin Grade 2 or 3. In our small study cohort, the HIPRENE treatment regime had higher nidus occlusion rates after the first treatment, which reduces the number of treatment sessions and lowers intra- and post-operative complication rates. Further randomized controlled studies are awaited to corroborate our preliminary outcomes.

Preoperative Embolization With Fused CT Angiography and Tractography Facilitates Safe Resection of a Spetzler-Martin Grade IV Arteriovenous Malformation

Brain arteriovenous malformations (BAVMs) are high-flow vascular lesions that have a propensity to rupture resulting in high rates of morbidity and mortality. Microsurgical resection of BAVMs is the standard of care for high-risk, resectable lesions. Multiple imaging modalities aid in the surgical planning and resection of high-grade BAVMs, but all have hidden variables that would prove useful if available. We present a 20-year-old male with a ruptured BAVM with concern for the involvement of the corticospinal tract (CST) and basal ganglia. We describe the melding of computed tomography angiography (CTA) and diffusion tensor imaging (DTI) in addition to preoperative embolization to aid in the planning and resection of a lesion close to eloquent structures. Post-operative CTA and DTI showed a total resection of the lesion with retained CST white matter tracts, and the patient retained the functional ability of the contralateral limbs. The combination of CTA, brain DTI, and preoperative embolization provides a framework to improve the safety of resection of BAVMs that occur near eloquent brain networks.

Simulation of superselective catheterization for cerebrovascular lesions using a virtual injection software

Background

This report addresses the feasibility of virtual injection software based on contrast-enhanced cone-beam CTs (CBCTs) in the context of cerebrovascular lesion embolization. Intracranial arteriovenous malformation (AVM), dural arteriovenous fistula (AVF) and mycotic aneurysm embolization cases with CBCTs performed between 2013 and 2020 were retrospectively reviewed. Cerebrovascular lesions were reviewed by 2 neurointerventionalists using a dedicated virtual injection software (EmboASSIST, GE Healthcare; Chicago, IL). Points of Interest (POIs) surrounding the vascular lesions were first identified. The software then automatically displayed POI-associated vascular traces from vessel roots to selected POIs. Vascular segments and reason for POI identification were recorded. Using 2D multiplanar reconstructions from CBCTs, the accuracy of vascular traces was assessed. Clinical utility metrics were recorded on a 3-point Likert scale from 1 (no benefit) to 3 (very beneficial).

Results

Nine cases (7 AVM, 1 AVF, 1 mycotic aneurysm) were reviewed, with 26 POIs selected. Three POIs were in 2nd order segments, 8 POIs in 3rd order segments and 15 POIs in 4th order segments of their respective arteries. The reviewers rated all 26 POI traces – involving a total of 90 vascular segments – as accurate. The average utility score across the 8 questions were 2.7 and 2.8 respectively from each reviewer, acknowledging the software’s potential benefit in cerebrovascular embolization procedural planning.

Conclusion

The operators considered CBCT-based virtual injection software clinically useful and accurate in guiding and planning cerebrovascular lesion embolization in this retrospective review. Future prospective studies in larger cohorts are warranted for validation of this modality.

Conventional and advanced MRI evaluation of brain vascular malformations

Vascular malformations (VMs) of the central nervous system (CNS) include a wide range of pathological conditions related to intra and extracranial vessel abnormalities. Although some VMs show typical neuroimaging features, other VMs share and overlap pathological and neuroimaging features that hinder an accurate differentiation between them. Hence, it is not uncommon to misclassify different types of VMs under the general heading of arteriovenous malformations. Thorough knowledge of the imaging findings of each type of VM is mandatory to avoid these inaccuracies. Conventional MRI sequences, including MR angiography, have allowed the evaluation of CNS VMs without using ionizing radiation. Newer MRI techniques, such as susceptibility-weighted imaging, black blood sequences, arterial spin labeling, and 4D flow imaging, have an added value of providing physiopathological data in real time regarding the hemodynamics of VMs. Beyond MR images, new insights using 3D printed models are being incorporated as part of the armamentarium for a noninvasive evaluation of VMs. In this paper, we briefly review the pathophysiology of CNS VMs, focusing on the MRI findings that may be helpful to differentiate them. We discuss the role of each conventional and advanced MRI sequence for VMs assessment and provide some insights about the value of structured reports of 3D printing to evaluate VMs.

Prospects of Photo- and Thermoacoustic Imaging in Neurosurgery

The evolution of neurosurgery has been, and continues to be, closely associated with innovations in technology. Modern neurosurgery is wed to imaging technology and the future promises even more dependence on anatomic and, perhaps more importantly, functional imaging. The photoacoustic phenomenon was described nearly 140 yr ago; however, biomedical applications for this technology have only recently received significant attention. Light-based photoacoustic and microwave-based thermoacoustic technologies represent novel biomedical imaging modalities with broad application potential within and beyond neurosurgery. These technologies offer excellent imaging resolution while generally considered safer, more portable, versatile, and convenient than current imaging technologies. In this review, we summarize the current state of knowledge regarding photoacoustic and thermoacoustic imaging and their potential impact on the field of neurosurgery.

A comparison of arterial spin labelling with catheter angiography in evaluating arteriovenous malformations: a systematic review

OBJECTIVES

To compare the performance of arterial spin labelling (ASL) in evaluating arteriovenous malformations (AVMs) against the current gold standard of catheter angiography.

METHODS

We systematically reviewed the published literature using EMBASE and Medline. We included studies that compared ASL to catheter angiography in the assessment of AVMs in three outcome domains: detection, angioarchitectural and haemodynamic features.

RESULTS

From 314 unique citations, 19 studies representing 289 patients with intracranial AVMs met our inclusion criteria. We did not pool data due to marked heterogeneity in study outcome measures. Seven studies showed high diagnostic performance of ASL in identifying arterial feeders, with sensitivity ranging from 84.6 to 100% and specificity ranging from 93.3 to 100%. Six studies showed strong ability in detecting arteriovenous shunting, with sensitivity ranging from 91.7 to 100% and specificity ranging from 90 to 100%. Seven studies demonstrated that ASL could identify nidal location and size as well as catheter angiography, while five studies showed relatively poorer performance in delineating venous drainage. Two studies showed 100% sensitivity of ASL in the identification of residual or obliterated AVMs following stereotactic radiosurgery.

CONCLUSIONS

Despite limitations in the current evidence base and technical challenges, this review suggests that ASL has a promising role in the work-up and post-treatment follow-up of AVMs. Larger scale prospective studies assessing the diagnostic performance of ASL are warranted.

ADVANCES IN KNOWLEDGE

ASL demonstrates overall validity in the evaluation of intracranial AVMs.

A Pericallosal Lipoma Case with Abnormal Vasculature Mimicking Arteriovenous Malformation

Pericallosal lipomas (PCLs) are rare tumors of the central nervous system. They may be associated with some parenchymal and vascular anomalies of brain. Magnetic resonance imaging is the modality of choice to assess the extent of the PCLs and possible concomitant malformations such as callosal agenesis/disgenesis. Computerized tomography angiography may be indicated to evaluate the vasculature of the lesion. We report here a case of PCL with rare features including asymptomatic callosal agenesis, bilateral choroid plexus lipomas and abnormal vasculature.

Overview of the current concepts in the management of arteriovenous malformations of the brain

Background

There is a lack of consensus in the management of arteriovenous malformations (AVMs) of the brain since ARUBA (A Randomised trial of Unruptured Brain Arteriovenous malformations) trial showed that medical management is superior to interventional therapy in patients with unruptured brain AVMs. The treatment of brain AVM is associated with significant morbidity.

Objectives and methods

A review was done to determine the behaviour of brain AVMs and analyse the risks and benefits of the available treatment options. A search was done in the literature for studies on brain AVMs. Descriptive analysis was also done.

Results

The angiogenic factors such as vascular endothelial growth factor and inflammatory cytokines are involved in the growth of AVMs. Proteinases such as matrix metalloproteinase-9 contribute to the weakening and rupture of the nidus. The risk factors for haemorrhage are prior haemorrhage, deep and infratentorial AVM location, exclusive deep venous drainage and associated aneurysms. The advancements in operating microscope and surgical techniques have facilitated microsurgery. Stereotactic radiosurgery causes progressive vessel obliteration over 2–3 years. Endovascular embolisation can be done prior to microsurgery or radiosurgery and for palliation.

Conclusions

Spetzler-Martin grades I and II have low surgical risks. The AVMs located in the cerebellum, subarachnoid cisterns and pial surfaces of the brainstem can be treated surgically. Radiosurgery is preferable for deep-seated AVMs. A combination of microsurgery, embolisation and radiosurgery is recommended for deep-seated and Spetzler-Martin grade III AVMs. Observation is recommended for grades IV and V.

Predictive Value of MRI in Diagnosing Brain AVM Recurrence after Angiographically Documented Exclusion in Children

BACKGROUND AND PURPOSE

MRI is routinely performed following brain AVM after treatment in children. Our aim was to determine the predictive values of contrast-enhanced MR imaging and TOF-MRA for brain AVM recurrence in children, compared with conventional angiography and the role of 3D rotational angiography-MR imaging fusion in these cases.

MATERIALS AND METHODS

We included all pediatric patients with brain AVMs during an 18-year period with angiographically documented obliteration after treatment. Patients underwent 3T MR imaging, including contrast-enhanced MR imaging, TOF-MRA, and conventional angiography, with a subset undergoing 3D rotational angiography. The predictive values of contrast-enhanced MR imaging and TOF-MRA for brain AVM recurrence were determined. CTA sections reconstructed from 3D rotational angiography were coregistered with and fused to 3D-T1WI for analysis.

RESULTS

Thirty-nine children (10.8 ± 3.9 years of age; range, 2-17 years; male/female ratio, 19:20; mean Spetzler-Martin grade, 1.9 ± 0.6) met the inclusion criteria. Of these, 13 had angiographically confirmed brain AVM recurrence, 8 following surgery and 5 following embolization. Sensitivity, specificity, and positive and negative predictive values for recurrence were the following: contrast-enhanced MR imaging: 84.6%, 38.5%, 40.7%, 81.8%; TOF-MRA: 50.0%, 96.1%, 85.7%, 79.3%; both: 75.0%, 90.9%, 85.7%, 83.3%. 3D rotational angiography-MR imaging fused images confirmed or excluded recurrence in all available cases (13/13). Embolization-only treatment was a significant predictor of recurrence (OR = 32.4, P = .006). MR imaging features predictive of recurrence included a tuft of vessels on TOF-MRA and nodular juxtamural/linear enhancement with a draining vein on contrast-enhanced MR imaging.

CONCLUSIONS

MR imaging is useful for surveillance after brain AVM treatment in children, but conventional angiography is required for definitive diagnosis of recurrence. TOF-MRA and contrast-enhanced MR imaging provide complementary information for determining brain AVM recurrence and should be interpreted in conjunction. 3D rotational angiography-MR imaging fusion increases the diagnostic confidence regarding brain AVM recurrence and is therefore suited for intraoperative neuronavigation.

MR Imaging in Neurocritical Care

How to cite this article: Patra A, Janu A, Sahu A. MR Imaging in Neurocritical Care. Indian J Crit Care Med 2019;23(Suppl 2):S104–S114.

[Atypical intracerebral hemorrhage-etiology and acute management]

Acute management as well as establishing the etiology of an intracerebral hemorrhage is still a challenge for clinicians. The location of the intracerebral hemorrhage alone should not be used to determine the cause because atypically located hemorrhages can be caused by long-standing arterial hypertension and typically located hemorrhages can occur due to non-hypertensive causes. Besides discussing the classification of intracerebral hemorrhages, this article focuses on a diagnostic algorithm as well as the presentation of potential (rarer) causes of non-traumatic intracerebral hemorrhages. Furthermore, the acute treatment of intracerebral hemorrhage with respect to recent data on blood pressure management as well as the management of bleeding under oral anticoagulant treatment are described.

Arterial-spin labeling MRI identifies residual cerebral arteriovenous malformation following stereotactic radiosurgery treatment

BACKGROUND AND PURPOSE

Brain arteriovenous malformation (AVM) treatment by stereotactic radiosurgery (SRS) is effective, but AVM obliteration following SRS may take two years or longer. MRI with arterial-spin labeling (ASL) may detect brain AVMs with high sensitivity. We determined whether brain MRI with ASL may accurately detect residual AVM following SRS treatment.

MATERIALS AND METHODS

We performed a retrospective cohort study of patients who underwent brain AVM evaluation by DSA between June 2010 and June 2015. Inclusion criteria were: (1) AVM treatment by SRS, (2) follow-up MRI with ASL at least 30 months after SRS, (3) DSA within 3 months of the follow-up MRI with ASL, and (4) no intervening AVM treatment between the MRI and DSA. Four neuroradiologists blindly and independently reviewed follow-up MRIs. Primary outcome measure was residual AVM indicated by abnormal venous ASL signal.

RESULTS

15 patients (12 females, mean age 29 years) met inclusion criteria. There were three posterior fossa AVMs and 12 supratentorial AVMs. Spetzler-Martin (SM) Grades were: SM1 (8%), SM2 (33%), SM3 (17%), SM4 (25%), and SM5 (17%). DSA demonstrated residual AVM in 10 patients. The pooled sensitivity, specificity, positive predictive value, and negative predictive value of venous ASL signal for predicting residual AVM were 100% (95% CI: 0.9-1.0), 95% (95% CI: 0.7-1.0), 98% (95% CI: 0.9-1.0), and 100% (95% CI: 0.8-1.0), respectively. High inter-reader agreement as found by Fleiss' Kappa analysis (k = 0.92; 95% CI: 0.8-1.0; P < 0.0001).

CONCLUSIONS

ASL is highly sensitive and specific in the detection of residual cerebral AVM following SRS treatment.