Evaluation of Intracranial Dural Arteriovenous Fistulas: Comparison of Unenhanced 3T 3D Time-of-flight MR Angiography with Digital Subtraction Angiography

Evaluating the diagnostic performance of non-contrast magnetic resonance angiography sequences in the pre-procedural comprehensive analysis of direct carotid cavernous fistula

PURPOSE

Endovascular treatment of direct carotid cavernous fistula (DCCF) requires invasive diagnostic cerebral angiography for diagnosis and planning; however, a less invasive modality like magnetic resonance angiography (MRA) can be useful, especially in high-risk cases. This single-centre study evaluated a newer MR angiography (MRA) sequence, silent MRA and the traditional time of flight (TOF) MRA for pre-procedural treatment planning of DCCF.

METHODS

All consecutive DCCF patients who underwent TOF, silent MRA and diagnostic cerebral angiography were included in the study. Angiographic features like rent size, location, draining veins and collateral communicating arteries were analysed and compared between the two MRA sequences, with digital subtraction angiography (DSA) as the gold standard.

RESULTS

Fifteen patients were included in the study. TOF MRA exhibited better sensitivity (76.9% vs 69.2%) in identifying the rent location, correctly pinpointing the location in 93.3% compared to 73.3% with silent MRA. Both MRA sequences showed good agreement with DSA for primary sac and rent size. TOF MRA correctly identified 86.2% of 210 total venous structures compared to 96% by silent MRA. Silent MRA demonstrated higher sensitivity (90% vs 76%) and accuracy (87.69 vs 94.36) in visualisation of involved veins compared to TOF MRA.

CONCLUSION

Arterial characteristics of DCCF like rent location and rent size were better assessed by TOF MRA. Although both MRA identified venous features, silent MRA correlated better with DSA irrespective of the size and proximity to the site of the fistula. Combining both sequences can evaluate various angioarchitectural features of DCCF useful for therapeutic planning.

Comparative study of non-contrast silent and time-of-flight magnetic resonance angiographic sequences in the evaluation of intracranial dural arteriovenous fistula

AIM

To compare the performance of two non-contrast magnetic resonance angiography (MRA) sequences, silent MRA and time of flight (TOF) MRA, in the evaluation of intracranial dural arteriovenous fistula (DAVF).

MATERIALS AND METHODS

Forty consecutive patients with DAVF were enrolled and evaluated prospectively using silent MRA, TOF MRA, and digital subtraction angiography (DSA). The location, Cognard classification, arterial feeders, and venous drainage were evaluated. The therapeutic strategy and possible route were predicted on both silent and TOF MRA and these were compared with DSA during subsequent endovascular treatment.

RESULTS

Sensitivity and accuracy of silent and TOF MRA for localisation (96.4% versus 96% and 96% versus 95%, respectively) and classification (96% versus 94% and 96% versus 93.5%, respectively) were high. Silent MRA showed higher sensitivity than TOF MRA for arterial feeders and draining veins (87% versus 79% and 81.6% versus 67%). This improved to a sensitivity of 96.4% and 89% when prominent feeders were considered. The sensitivity and accuracy were 92.6% and 85.8% for immediate draining veins. Both silent and TOF MRA were accurate for therapeutic planning (96% versus 85%), although silent MRA was more accurate.

CONCLUSION

Silent MRA can more reliably evaluate the various angioarchtectural components of DAVF compared to TOF MRA.

Intracranial Dural Arteriovenous Fistulas

Dural arteriovenous fistulas (DAVFs) are abnormal communications between meningeal arteries and dural venous sinuses and/or cortical veins. Although many fistulas are benign and do not require treatment, some may carry a significant risk of bleeding or cause symptoms and warrant treatment. This review provides a review of various aspects of intracranial DAVFs including epidemiology, pathophysiology, clinical presentation, imaging characteristics, classification, natural history, and management options. By exploring these topics, we aim to enhance understanding of this condition and facilitate patient care.

Non-invasive angiographic analysis of dural carotid cavernous fistula using time-of-flight MR angiography and silent MR angiography: a comparative study

BACKGROUND

A non-invasive, reliable imaging modality that characterizes cavernous sinus dural arteriovenous fistula (CSDAVF) is beneficial for diagnosis and to assess resolution on follow-up.

PURPOSE

To assess the utility of 3D time-of-flight (TOF) and silent magnetic resonance angiography (MRA) for evaluation of CSDAVF from an endovascular perspective.

MATERIAL AND METHODS

This prospective study included 37 patients with CSDAVF, who were subjected to digital subtraction angiography (DSA) and 3-T MR imaging with 3D TOF and silent MRA. The main arterial feeders, fistula site, and venous drainage pattern were evaluated, and the results were compared with DSA findings. The diagnostic confidence scores were also recorded using a 4-point Likert scale.

RESULTS

Silent MRA correlated better for shunt site localization and angiographic classification (86% vs. 75% and 83% vs. 75%, respectively) compared to TOF MRA. The proportion of arterial feeders detected was marginally significant for silent MRA over TOF MRA sequences (92.8% vs. 89.5%; P=0.048), though for veins both were comparable. Sensitivity of silent MRA was higher for identification of cortical venous reflux (CVR) (90.9% vs. 81.8%) and deep venous drainage (82.4% vs. 64.7%), while specificity was >90% for both modalities. The overall diagnostic confidence score fared better for silent MRA for venous assessment (P < 0.001) as well as fistula point identification (P < 0.001), while no significant difference was evident with TOF MRA for arterial feeders (P=0.06).

CONCLUSION

Various angiographic components of CSDAVF could be identified and delineated by 3D TOF and silent MRA, though silent MRA was superior for overall diagnostic assessment.

[Cerebral dural arteriovenous fistulas]

CLINICAL ISSUE

The cerebral dural arteriovenous (AV) fistula is a rare cerebral vascular malformation. Clinical presentation varies from asymptomatic to acute intracranial bleeding. Classification is based on the venous drainage with a risk assessment of bleeding. The carotid-cavernous fistula is a subtype with its own classification and treatment approaches.

PRACTICAL RECOMMENDATIONS

Nowadays, dural fistulas can be diagnosed using high-resolution and time-resolved tomographic methods. Catheter angiography with subsequent interdisciplinary discussion should be performed for precise classification and therapy planning. Both endovascular and surgical treatment methods are available.

MRI and MR angiography evaluation of pulsatile tinnitus: A focused, physiology-based protocol

BACKGROUND AND PURPOSE

Pulsatile tinnitus (PT) is the subjective sensation of a pulse-synchronous sound, most often due to a cerebrovascular etiology. PT can severely impact quality of life and may indicate a life-threatening process, yet a timely and accurate diagnosis can often lead to effective treatment. Clinical assessment with a history and physical examination can often suggest a diagnosis for PT, but is rarely definitive. Therefore, PT should be evaluated with a comprehensive and targeted radiographic imaging protocol. MR imaging provides a safe and effective means to evaluate PT. Specific MR sequences may be used to highlight different elements of cerebrovascular anatomy and physiology. However, routine MR evaluation of PT must comply with economic and practical constraints, while effectively capturing both common and rarer, life-threatening etiologies of PT.

METHODS

In this state-of-the-art review, we describe our institutional MR protocol for evaluating PT.

RESULTS

This protocol includes the following dedicated sequences: time-of-flight magnetic resonance angiography; arterial spin labeling; spoiled gradient recalled acquisition in the steady state; time-resolved imaging of contrast kinetics; diffusion weighted imaging, and 3-dimensional fluid-attenuated inversion recovery.

CONCLUSIONS

We describe the physiologic and clinical rationale for including each MR sequence in a comprehensive PT imaging protocol, and detail the role of MR within the broader evaluation of PT, from clinical presentation to treatment.

Endovascular Management of Intracranial Dural AVFs: Principles

Intracranial dural AVFs are abnormal communications between arteries that supply the dura mater and draining cortical veins or venous sinuses. They are believed to form as a response to venous insults such as thrombosis, trauma, or infection. Classification and management are dependent on the presence of drainage/reflux into cortical veins because such drainage markedly elevates the risk of hemorrhage or venous congestion, resulting in neurologic deficits. AVFs with tolerable symptoms and benign drainage patterns can be managed conservatively. Intolerable symptoms, presentation with hemorrhage/neurologic deficits, or aggressive drainage patterns are indications for intervention. Treatment options include microsurgical disconnection, endovascular transarterial embolization, transvenous embolization, or a combination. This is the first in a series of 3 articles on endovascular management of intracranial dural AVFs, in which we outline the principles and outcomes of endovascular treatment.

Results of transvenous embolization of intracranial dural arteriovenous fistula: a consecutive series of 136 patients with 142 fistulas

OBJECTIVE

Intracranial dural arteriovenous fistula (DAVF) is mainly treated with an endovascular approach. Two major treatment advances include transvenous embolization (TVE) with coils in 1989 and, more recently, transarterial embolization with Onyx. The aim of this study was to present a large monocentric series of patients with DAVF treated with TVE. This series reports more than 20 years of experience and describes the evolution of the medical management of these patients, as well as current indications for this treatment at the authors' center.

METHODS

Consecutive patients treated for intracranial DAVFs with TVE from 1995 to 2018 were included. Clinical and imaging data were systematically collected. Univariate and multivariate analyses were performed to identify factors that were significantly associated with adverse clinical course or complications.

RESULTS

In this study of 136 patients with 142 DAVFs treated with TVE, the occlusion rate was 90%. The median length of follow-up was 11 months. The rate of permanent complications was 5.1%, and the procedure-related mortality rate was 1.5%. Procedure-related mortality was associated with extension of thrombosis that was observed early in our experience. The introduction of a postoperative anticoagulation regimen has drastically decreased the occurrence of this complication. Other minor complications included cochleovestibular syndrome after embolization of lateral sinus DAVF and oculomotor nerve damage after embolization of cavernous sinus DAVF.

CONCLUSIONS

TVE allows efficient occlusion of DAVF. It remains a valid option for DAVF located on a sinus that does not participate in normal venous drainage of the brain.

ACR Appropriateness Criteria® Cerebrovascular Diseases-Aneurysm, Vascular Malformation, and Subarachnoid Hemorrhage

Cerebrovascular disease is a broad topic. This document focuses on the imaging recommendations for the varied clinical scenarios involving intracranial aneurysms, vascular malformations, and vasculitis, which all carry high risk of morbidity and mortality. Additional imaging recommendations regarding complications of these conditions, including subarachnoid hemorrhage and vasospasm, are also covered. While each variant presentation has unique imaging recommendations, the major focus of this document is neurovascular imaging techniques. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Transarterial embolization of dural arteriovenous fistulas of the lateral sinuses with stent-assisted sinus protection

BACKGROUND

The balloon-assisted sinus protection technique has been described as a sinus-preserving technique during transarterial embolization (TAE) of dural arteriovenous fistulas (DAVFs). However, some serious complications of this technique have been documented.

OBJECTIVE

To describe our preliminary experience with a new technique called stent-assisted sinus protection (SSP).

METHODS

We performed a retrospective analysis of seven consecutive patients with type I or IIa DAVFs of the lateral sinus treated by TAE with a closed-cell stent temporarily deployed in the sinus.

RESULTS

Of the seven patients, four had type I DAVF, and three had type IIa DAVF. The patency of all involved sinuses and their tributaries (including the inferior anastomotic vein and the superior petrosal sinus) was preserved. At the end of the procedure, all stents were successfully retrieved with embolic particles trapped in their meshes. No procedural complications were noted. Clinical follow-up was satisfactory, with complete resolution or significant reduction of pulsatile tinnitus.

CONCLUSIONS

SSP appears to be feasible and probably safe. However, larger studies are needed to confirm these preliminary results.

Dilated MMA sign in cDAVF and other arterial feeders on 3D TOF MRA

Background

Among the varied causes of pulsatile tinnitus, the condition that can cause severe mortality and morbidity is a cranial dural arteriovenous fistula (cDAVF). This study aimed to assess the diagnostic accuracy of the dilated middle meningeal artery on three-dimensional time-of-flight magnetic resonance angiography in cranial dural arteriovenous fistula and to identify other feeders that can aid in the detection of these lesions.

Method

Magnetic resonance angiography and digital subtraction angiography data of all patients with cranial dural arteriovenous fistula treated in a single tertiary referral center between 2007–2020 were included. The middle meningeal artery and other feeders recorded from digital subtraction angiography were assessed on magnetic resonance angiography.

Results

The overall agreement between readers in identifying the dilated middle meningeal artery was substantial (κ = 0.878, 95% confidence interval: 0.775–0.982). The dilated middle meningeal artery indicated the presence of a cranial dural arteriovenous fistula with a sensitivity of 79.49% (95% confidence interval: 66.81–92.16), specificity of 100% (95% confidence interval: 100.00–100.00), and negative predictive value of 94.56% (95% confidence interval: 90.89–98.02). An area under the curve of 0.8341 was observed for the ipsilateral middle meningeal artery, with a sensitivity of 92.2% and a specificity of 75.0% at a cut-off of 0.30 mm for identifying a cranial dural arteriovenous fistula. Of 73 other feeders, the occipital, meningohypophyseal trunk, ascending pharyngeal, and posterior meningeal arteries contributed to a large proportion visualized on magnetic resonance angiography (83.6% (41/49)).

Conclusion

The dilated middle meningeal artery sign is useful for identifying a cranial dural arteriovenous fistula. Dilatation of the occipital and ascending pharyngeal arteries and meningohypophyseal trunk should be assessed to facilitate the detection of a cranial dural arteriovenous fistula, particularly in the transverse-sigmoid and petrous regions.

Utility of silent magnetic resonance angiography in the evaluation and characterisation of intracranial dural arteriovenous fistula

AIM

To evaluate the utility of silent magnetic resonance angiography (MRA) in the diagnosis, characterisation, and therapeutic planning of intracranial dural arteriovenous fistula (DAVF).

MATERIALS AND METHODS

Twenty consecutive patients with DAVF were enrolled prospectively and were evaluated using silent MRA and digital subtraction angiography (DSA) as a part of routine work-up. The diagnosis and location of fistula, Borden and Cognard classification, entire arterial feeders, and venous drainage were analysed. A therapeutic strategy was formulated, and the accessible route and vessel were predicted, which was confirmed on endovascular treatment.

RESULTS

Silent MRA was 100% sensitive and accurate for location and classification of fistulas. Silent MRA showed a sensitivity of 82% and 76.5% for entire arterial feeders and draining veins, which improved to a sensitivity of 90% and 94% when prominent feeders and immediate venous drainage was considered. Among the missed veins, thrombosed sinus, slow sinus flow, small calibre, reduced image quality were the causes. The therapeutic decision matched with DSA in all cases and silent MRA accurately identified the potential accessible feeder in 94% cases.

CONCLUSION

Silent MRA is a promising MR technique that can provide both diagnostic and therapeutic information similar to that obtained from DSA.

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.

Impaired meningeal lymphatic drainage in patients with idiopathic Parkinson's disease

Animal studies implicate meningeal lymphatic dysfunction in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease (PD). However, there is no direct evidence in humans to support this role^1-5. In this study, we used dynamic contrast-enhanced magnetic resonance imaging to assess meningeal lymphatic flow in cognitively normal controls and patients with idiopathic PD (iPD) or atypical Parkinsonian (AP) disorders. We found that patients with iPD exhibited significantly reduced flow through the meningeal lymphatic vessels (mLVs) along the superior sagittal sinus and sigmoid sinus, as well as a notable delay in deep cervical lymph node perfusion, compared to patients with AP. There was no significant difference in the size (cross-sectional area) of mLVs in patients with iPD or AP versus controls. In mice injected with α-synuclein (α-syn) preformed fibrils, we showed that the emergence of α-syn pathology was followed by delayed meningeal lymphatic drainage, loss of tight junctions among meningeal lymphatic endothelial cells and increased inflammation of the meninges. Finally, blocking flow through the mLVs in mice treated with α-syn preformed fibrils increased α-syn pathology and exacerbated motor and memory deficits. These results suggest that meningeal lymphatic drainage dysfunction aggravates α-syn pathology and contributes to the progression of PD.

Quantification of intracranial arterial stenotic degree evaluated by high-resolution vessel wall imaging and time-of-flight MR angiography: reproducibility, and diagnostic agreement with DSA

OBJECTIVES

The purpose of this study was to compare the reproducibility and diagnostic agreement of high-resolution vessel wall imaging (HR-VWI) and time-of-flight magnetic resonance angiography (TOF-MRA) with digital subtraction angiography (DSA) to evaluate intracranial arterial stenosis.

METHODS

We retrospectively enrolled patients who underwent HR-VWI and TOF-MRA with suspected intracranial artery disease and had DSA results from our institutional imaging database. Two neuroradiologists separately and independently evaluated anonymous image data for the stenotic lesions. DSA was analyzed by two neurointerventionalists and it served as a standard criterion. The reproducibility of these two MR techniques was determined by the intraclass correlation coefficients (ICCs). The diagnostic agreement to DSA was assessed by the concordance correlation coefficients (CCCs).

RESULTS

A total of 246 lesions from 106 individuals were analyzed for stenotic degrees. The total intra-observer and inter-observer reproducibility of HR-VWI was excellent for identifying stenosis and better than of TOF-MRA. The overall concordance of HR-VWI with DSA was excellent with CCC = 0.932, whereas TOF-MRA was 0.694. In addition, HR-VWI could provide additional vessel wall information.

CONCLUSIONS

HR-VWI has more advantages over TOF-MRA, such as better reproducibilities and diagnostic agreements with DSA to analyze intracranial arterial stenosis. It provides additional information that helps in clinical diagnosis and management.

KEY POINTS

• High-resolution vessel wall imaging can assess intracranial arterial stenosis with a better reproducibility than TOF-MRA and has a higher diagnostic agreement with DSA. • High-resolution vessel wall imaging had a higher diagnostic agreement with DSA compared with TOF-MRA. • Apart from evaluating vascular stenosis, HR-VWI provided additional vessel wall information to help in clinical diagnosis.

Evaluation of cerebral arteriovenous shunts: a comparison of parallel imaging time-of-flight magnetic resonance angiography (TOF-MRA) and compressed sensing TOF-MRA to digital subtraction angiography

PURPOSE

Time-of-flight (TOF)-MR angiography (MRA) is an important imaging sequence for the surveillance and analysis of cerebral arteriovenous shunt (AVS), including arteriovenous malformation (AVM) and arteriovenous fistula (AVF). However, this technique has the disadvantage of a relatively long scan time. The aim of this study was to compare diagnostic accuracy between compressed sensing (CS)-TOF and conventional parallel imaging (PI)-TOF-MRA for detecting and characterizing AVS.

METHODS

This study was approved by the institutional review board for human studies. Participants comprised 56 patients who underwent both CS-TOF-MRA and PI-TOF-MRA on a 3-T MR unit with or without cerebral AVS between June 2016 and September 2018. Imaging parameters for both sequences were almost identical, except the acceleration factor of 3× for PI-TOF-MRA and 6.5× for CS-TOF-MRA, and the scan time of 5 min 19 s for PI-TOF-MRA and 2 min 26 s for CS-TOF-MRA. Two neuroradiologists assessed the accuracy of AVS detection on each sequence and analyzed AVS angioarchitecture. Concordance between CS-TOF, PI-TOF, and digital subtraction angiography was calculated using unweighted and weighted kappa statistics.

RESULTS

Both CS-TOF-MRA and PI-TOF-MRA yielded excellent sensitivity and specificity for detecting intracranial AVS (reviewer 1, 97.3%, 94.7%; reviewer 2, 100%, 100%, respectively). Interrater agreement on the angioarchitectural features of intracranial AVS on CS-MRA and PI-MRA was moderate to good.

CONCLUSION

The diagnostic performance of CS-TOF-MRA is comparable to that of PI-TOF-MRA in detecting and classifying AVS with a reduced scan time under 2.5 min.

Spontaneous closure of non-cavernous sinus dural arteriovenous fistulas: A case series and systematic review of the literature

BACKGROUND AND PURPOSE

To report 9 new cases of non-cavernous sinus dural arteriovenous fistulas (NCS-DAVFs) that closed spontaneously and systematically review reports of other cases in the literature.

MATERIAL AND METHODS

We performed a retrospective analysis of 9 cases from 2 institutions of NCS-DAVFs that closed spontaneously. Using PubMed and Scopus in accordance with the PRISMA guidelines, we systematically reviewed English language articles about NCS-DAVFs showing spontaneous closure.

RESULTS

Review of the cases from 2 institutions identified 9 cases of NCS-DAVFs showing spontaneous closure in follow-up magnetic resonance angiography (MRA), and the systematic review of the literature yielded an additional 38 cases, which had been diagnosed by repeated arteriography. Collectively, the patients included 23 men and 24 women with a mean age of 54 years. The shunts were located in the transverse-sigmoid sinus in 24 cases (51%), anterior condylar confluence in 11, and other locations in 12. Based on the venous drainage pattern on arteriography, 27 cases (57%) were classified as low-risk NCS-DAVF (without cortical venous reflux) and 17 were classified as high-risk NCS-DAVF (with cortical venous reflux). Shunt closure was observed within 3 months in 17 cases (36%). Extrinsic predisposing factors for shunt closure were detected in 14 cases (30%). These included angiography in 7 cases, sinus recanalization in 4, development of sinus occlusion in 2, and sinus compression by a newly developed hematoma in 1.

CONCLUSION

Spontaneous closures of NCS-DAVFs can occur for both high- and low-risk types. One-third of these closures occur within 3 months.

Unusual cortical symptoms of dural arteriovenous fistula mimicking transient ischemic attack

The clinical presentation of dural arteriovenous fistula (DAVF) can vary. A 47-year-old man complained of transient difficulty playing badminton and speech disturbance for 10 minutes. His symptoms were suspected to be visuomotor coordination deficit similar to optic ataxia and anomic aphasia. Magnetic resonance imaging and angiography revealed vasogenic edema and perfusion delay in the left temporo-occipital area and an abnormal connection between the left occipital artery and transverse sinus. Transverse sinus DAVF was diagnosed by conventional cerebral angiography. We believe that this is the unique case of DAVF manifested as visuomotor coordination deficit suspected optic ataxia and anomic aphasia.

Magnetic resonance imaging as a single diagnostic tool for verifying radiosurgery outcomes of cavernous sinus dural arteriovenous fistula

PURPOSE

MRI and MR angiography (MRA) are noninvasive methods for examining cavernous sinus dural arteriovenous fistulas (CSDAVFs) after radiosurgery. In this study, we investigated the accuracy of unenhanced MRI/3-dimensional time-of-flight (3D TOF) MRA in evaluating CSDAVF obliteration as compared with digital subtraction angiography (DSA).

METHODS

From 1995-2012, 48 cases of CSDAVFs received Gamma Knife surgery (GKS) and had undergone both unenhanced MRI/3D TOF MRA and DSA for posttreatment evaluation. Two blinded observers independently interpreted the results of MRI/MRA. The results of MRI/MRA were compared with those of DSA. The sensitivity (the probability of MRI/MRA showing obliteration when DSA showed complete obliteration), specificity, positive predictive value, and negative predictive value for CSDAVF obliteration were reported.

RESULTS

The median interval between the final MRI/MRA and the subsequent DSA was 2 months. Follow-up DSA revealed that 38 of 48 (79.2 %) CSDAVFs were completely obliterated. The results of interobserver agreement assessment showed almost perfect agreement between the 2 observers. For unenhanced MRI/3D TOF MRA, the observed sensitivity was 84.2 %, specificity was 100 %, positive predictive value was 100 %, and negative predictive value was 62.5 %.

CONCLUSIONS

Unenhanced MRI/3D TOF MRA alone may be adequate to document the complete obliteration of CSDAVFs after GKS. Time-resolved MRA or DSA can be reserved for a suspected residual CSDAVF after a sufficient latency period after GKS.

Treatment Outcomes According to Various Treatment Modalities for Intracranial Dural Arteriovenous Fistulas in the Onyx Era: A 10-Year Single-Center Experience

BACKGROUND

Although transarterial embolization (TAE) with Onyx has become popular for the treatment of dural arteriovenous fistulas (DAVFs), transvenous embolization (TVE), surgery, and radiosurgery have continued to have a role. The aim of the present study was to compare the treatment outcomes stratified by the different treatment modalities.

METHODS

The data from 92 patients with DAVFs treated from January 2009 to June 2018 were retrospectively reviewed. The treatment strategies were decided by a multidisciplinary team according to the patient's clinical status and angiographic findings. The clinical and radiologic data were analyzed and correlated with the treatment modality.

RESULTS

A total of 101 procedures were performed in the 92 patients. TAE, TVE, surgery, and radiosurgery were performed in 31, 49, 12, and 9 procedures, respectively. Complete and near complete occlusion was achieved in 13 cases treated with TAE (41.9%), 41 treated with TVE (83.7%), and 10 with surgery (83.3%), as shown on immediate postprocedural angiography (P < 0.001). Retreatment was needed in 9 patients in the TAE group and none in the TVE or surgery groups (P < 0.001). Surgery (n = 1), TVE (n = 3), TAE (n = 1), and radiosurgery (n = 4) were used for patients requiring retreatment. At the last follow-up examination (mean, 26.5 ± 23.9 months), 66 of 72 DAVFs (91.6%) showed angiographic complete occlusion. Clinically, the initial symptoms had disappeared or improved in 87 of 90 patients (96.7%) at the last follow-up evaluation (mean, 26.4 ± 26.8 months).

CONCLUSIONS

Even in the Onyx era, other treatment modalities still have important roles, as shown in the present study. Therefore, the selection of the appropriate treatment modality should be individualized by the angiographic findings and clinical symptoms.

Current status of endovascular treatment for dural arteriovenous fistulae in the tentorial middle region: a literature review

The tentorial middle region (TMR) includes the midline and paramedian tentorium. TMR dural arteriovenous fistulae (DAVFs) are complex. We performed a review of the literature on TMR DAVFs. TMR DAVFs are divided into the following four types: incisural DAVF, Galenic DAVF, straight sinus DAVF and torcular DAVF. TMR DAVFs often drain into pial veins; therefore, most TMR DAVFs are classified as Borden II-III and Cognard types IIb-IV, whose characteristics cause TMR DAVFs to be prone to hemorrhage. TMR DAVFs have a very disappointing natural progression, and treatment is necessary. TMR DAVFs have extensive arterial supply and complex venous drainages, making them difficult to treat. Currently, for TMR DAVF, endovascular treatment (EVT) has become a better option. In EVT, transarterial embolization is the first-line treatment. Many complications can occur when treating TMR DAVFs, but complete EVT can generally achieve good clinical outcomes. In this review, three educational cases with demonstrating figures are provided to elaborate TMR DAVFs.

Non contrast, Pseudo-Continuous Arterial Spin Labeling and Accelerated 3-Dimensional Radial Acquisition Intracranial 3-Dimensional Magnetic Resonance Angiography for the Detection and Classification of Intracranial Arteriovenous Shunts

OBJECTIVES

The aim of this study was to assess the sensitivity and specificity of pseudo-continuous arterial spin labeling (PCASL) magnetic resonance angiography (MRA) with 3-dimensional (3D) radial acquisition for the detection of intracranial arteriovenous (AV) shunts.

MATERIALS AND METHODS

A total of 32 patients who underwent PCASL-MRA, clinical magnetic resonance imaging (MRI)/MRA exam, and digital subtraction angiography (DSA) were included in this retrospective analysis. Twelve patients presented with AV shunts. Among these were 8 patients with AV malformations (AVM) and 4 patients with AV fistulas (AVF). The clinical MRI/MRA included 3D time-of-flight MRA in all cases and time-resolved, contrast-enhanced MRA in 9 cases (6 cases with AV shunting). Research MRI and clinical MRI were independently evaluated by 2 neuroradiologists blinded to patient history. A third radiologist evaluated DSA imaging. A diagnostic confidence score was used for the presence of abnormalities associated with AV shunting (1-5). The AVMs were characterized using the Spetzler-Martin scale, whereas AVFs were characterized using the Borden classification. κ Statistics were applied to assess intermodality agreement.

RESULTS

Compared with clinical MRA, noncontrast PCASL-MRA with 3D radial acquisition yielded excellent sensitivity and specificity for the detection of intracranial AV shunts (reader 1: 100%/100%, clinical MRA: 91.7%, 94.4%; reader 2: 91.7%/100%, clinical MRA: 91.7%/100%). Diagnostic confidence was 4.8/4.66 with PCASL-MRA and 4.25/4.66 with clinical MRA. For AVM characterization with PCASL-MRA, intermodality agreement with DSA showed κ values of 0.43 and 0.6 for readers 1 and 2, respectively. For AVF characterization, intermodality agreement showed κ values of 0.56 for both readers.

CONCLUSION

Noncontrast PCASL-MRA with 3D radial acquisition is a potential tool for the detection and characterization of intracranial AV shunts with a sensitivity and specificity equivalent or higher than routine clinical MRA.

Three-dimensional multimodality fusion imaging as an educational and planning tool for deep-seated meningiomas

INTRODUCTION

The utility of surgical simulation with three-dimensional multimodality fusion imaging (3D-MFI) has been demonstrated. However, its potential in deep-seated brain lesions remains unknown. The aim of this study was to investigate the impact of 3D-MFI in deep-seated meningioma operations.

MATERIAL AND METHODS

Fourteen patients with deeply located meningiomas were included in this study. We constructed 3D-MFIs by fusing high-resolution magnetic resonance (MR) and computed tomography (CT) images with a rotational digital subtraction angiogram (DSA) in all patients. The surgical procedure was simulated by 3D-MFI prior to operation. To assess the impact on neurosurgical education, the objective values of surgical simulation by 3D-MFIs/virtual reality (VR) video were evaluated. To validate the quality of 3D-MFIs, intraoperative findings were compared. The identification rate (IR) and positive predictive value (PPV) for the tumor feeding arteries and involved perforating arteries and veins were also assessed for quality assessment of 3D-MFI.

RESULTS

After surgical simulation by 3D-MFIs, near-total resection was achieved in 13 of 14 (92.9%) patients without neurological complications. 3D-MFIs significantly contributed to the understanding of surgical anatomy and optimal surgical view (p < .0001) and learning how to preserve critical vessels (p < .0001) and resect tumors safety and extensively (p < .0001) by neurosurgical residents/fellows. The IR of 3D-MFI for tumor-feeding arteries and perforating arteries and veins was 100% and 92.9%, respectively. The PPV of 3D-MFI for tumor-feeding arteries and perforating arteries and veins was 98.8% and 76.5%, respectively.

CONCLUSIONS

3D-MFI contributed to learn skull base meningioma surgery. Also, 3D-MFI provided high quality to identify critical anatomical structures within or adjacent to deep-seated meningiomas. Thus, 3D-MFI is promising educational and surgical planning tool for meningiomas in deep-seated regions.

Prospective motion correction enables highest resolution time-of-flight angiography at 7T

PURPOSE

Higher magnetic field strengths enable time-of-flight (TOF) angiography with higher resolution to depict small-vessel pathologies. However, this potential is limited by the subject's ability to remain motionless. Even small-scale, involuntary motion can degrade vessel depiction, thus limiting the effective resolution. The aim of this study was to overcome this resolution limit by deploying prospectively motion-corrected (PMC) TOF.

METHODS

An optical, marker-based, in-bore tracking system was used to update the imaging volume prospectively according to the subject's head motion. PMC TOF was evaluated in 12 healthy, cooperative subjects at isotropic resolution of up to 150 μm. Image quality was assessed qualitatively through reader rating and quantitatively with the average edge-strength metric.

RESULTS

PMC significantly increased the average edge strength and qualitatively improved the vessel depiction in nine out of 11 cases. Image quality was never degraded by motion correction. PMC also enabled acquisition of the highest resolution human brain in vivo TOF angiography to date.

CONCLUSION

With PMC enabled, high-resolution TOF is able to visualize brain vasculature beyond the effective resolution limit. Magn Reson Med 80:248-258, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Progress in research on intracranial multiple dural arteriovenous fistulas

Intracranial multiple dural arteriovenous fistulas (MDAVFs) are rare lesions that are difficult to treat. The key factors involved in the development of MDAVFs remain unknown. At present, the majority of reports on intracranial MDAVFs are confined to case reports and small case series, and thus understanding of MDAVFs is limited. The current review assesses the available literature to date with the aim of reviewing the progress in research on intracranial MDAVFs. Intracranial MDAVFs may be divided into two types: Synchronous and metachronous. While the exact pathogenesis of MDAVFs is unknown, a number of possible mechanisms are considered relevant. The first is that MDAVFs develop following recanalization of a large sinus thrombosis that involves several sinuses. The second possibility is that a pre-existing DAVF may induce sinus thrombosis or venous hypertension, resulting in a new MDAVF. The third is that MDAVFs are caused by increased angiogenic activity, which may induce the development of MDAVFs. Intracranial MDAVFs have a malignant clinical course, and their symptoms generally rapidly progress following onset. It is therefore important to identify intracranial MDAVFs at an early stage. A number of imaging technologies, including computed tomography (CT), magnetic resonance imaging (MRI), digital subtraction angiography (DSA) and single-photon emission computed tomography (SPECT), may be used to detect MDAVFs. Of these, CT and MRI provide information on brain morphology, SPECT provides brain blood flow information, and DSA is the gold standard that may be used to identify angioarchitecture and hemodynamics. MDAVFs require timely and aggressive treatment, which may include endovascular embolization, surgical resection, radiosurgery and conservative treatment, and in some cases, combined treatments are required. Appropriate and aggressive treatment regimens can markedly improve neurological deficits and cognitive function in patients with MDAVFs.