Simultaneous arteriovenous shunting and venous congestion identification in dural arteriovenous fistulas using susceptibility-weighted imaging: initial experience

The "Hypointense Focal Brain" on susceptibility-weighted imaging as a sign of venous congestion in cranial dural arteriovenous fistulas

BACKGROUND

Cranial dural arteriovenous fistulas (dAVFs) are complex neurovascular malformations accounting for approximately 10%-15% of all intracranial arteriovenous malformations. The objective is to investigate the utility of susceptibility-weighted imaging (SWI) in identifying "hypointense focal brain" as an additional helpful sign of venous congestion in cranial dAVFs.

MATERIALS AND METHODS

A retrospective review of patients diagnosed with cranial dAVFs between January 2015 and June 2023 was conducted, and SWI was used to identify the "hypointense focal brain" sign within the venous drainage region of the dAVF. The "hypointense focal brain" on SWI was identified as a low-intensity signal within the venous drainage region, indicative of venous congestion. The presence of this imaging sign was assessed by two neuroradiologists and signal intensity measurements were performed to support the presence of the sign.

RESULTS

The study included six patients with cranial dAVFs exhibiting cortical venous retrograde drainage and the "hypointense focal brain" on SWI. Follow-up imaging post-treatment revealed resolution or improvement of the hypointense signal, confirming its association with venous congestion. Signal intensity measurements further supported the presence of this imaging sign in pre-treatment scans.

CONCLUSION

The study's findings demonstrate the presence of a reversible "hypointense focal brain" sign on SWI in patients with cranial dAVFs and CVR, which can be useful as an additional imaging sign for venous congestion.

The 'corkscrew' sign: an indirect MRI hint for intracranial venous hypertension

Dural arteriovenous fistulas (DAVFs) are intracranial vascular abnormalities in which one or more meningeal arteries shunt into a venous structure, either a cortical vein or a venous sinus, causing cerebral venous hypertension and risk of haemorrhage. Imaging diagnosis and characterisation are of paramount importance to grade the haemorrhagic risk and direct management. Non-invasive vascular neuroimaging might pose a diagnostic suspicion, but invasive catheter digital subtraction angiography (DSA) is usually required. We present the case of a patient with an atypical acute cerebral haemorrhage in which admission imaging with CT angiography (CTA) and MR angiography (MRA) was unremarkable, while advanced morphological MR with susceptibility-weighted imaging (SWI) revealed specific findings suggesting unilateral chronic venous hypertension. Successively, DSA detected a small DAVF that was treated with endovascular embolization. This case report raises awareness on subtle but important conventional imaging findings that suggest the presence of an AV shunt, to avoid misdiagnosis and delayed treatment.

Susceptibility weighted imaging for qualitative grading of persistent arteriovenous shunting in deep-seated arteriovenous malformations after stereotactic radiation surgery

BACKGROUND AND PURPOSE

To investigate Susceptibility Weighted Imaging (SWI) signal changes in the draining vein of deep-seated arterio-venous malformations (AVMs) following stereotactic radiosurgery (SRS).

METHODS AND MATERIALS

This is a retrospective study of 32 patients with deep-seated AVMs who were treated with SRS. Pre-SRS treatment and post-SRS treatment MRI were performed at 6, 12, and 24-month intervals. Deep-seated AVMs were classified based on their anatomical location and venous drainage pattern. AVM nidal volume (cm3) was estimated using the ABC/2 method. AV shunting of the AVM draining veins were graded according to its SWI signal intensity: hyperintense (grade III), mixed signal intensity (grade II), hypointense (grade I) and absent (grade 0). Conventional time-of-flight (TOF)-MRA and contrast enhanced (CE)-MRA sequences were performed to document the patency of the vein.

RESULTS

Pre-SRS treatment AVM draining veins were either grade III 18/32 (56%) or grade II 14/32 (44%). Using mixed effects analysis, we demonstrate that each month following the SRS treatment nidal volumes decreased at the rate of 0.51 cm3/per month (CI -0.61 to (-0.40)) p =.00. Following the treatment, there was a clinically significant relationship between the signal and nidal volume: signal 0 corresponded with average nidal volume of 1.81 cm3 (CI 1.40-2.21), signal 1 with nidal volume of 2.06 cm3 (CI 1.69-2.44), signal 2 with nidal volume 2.73 cm3 (CI 2.35-3.11) and signal 3 with nidal volume 3.13 cm3 (CI 2.70-3.56) p = .00.

CONCLUSION

Post-SRS AVM draining veins shows a stepwise regression of the SWI signal grades which can be reliably used as a surrogate to monitor the reduction of AV shunting.

Differentiation between aggressive and benign intracranial non-cavernous dural arteriovenous fistulas using cortical venous reflux on susceptibility weighted images

PURPOSE

This study aimed to evaluate the ability of susceptibility-weighted imaging (SWI) to detect cortical venous reflux (CVR) in patients with intracranial non-cavernous dural arteriovenous fistulas (DAVFs), which can be helpful to differentiate benign and aggressive DAVFs.

MATERIAL AND METHODS

Twenty-seven patients (8 women and 19 men) with 33 non-cavernous DAVFs were divided into benign and aggressive groups. Presence of CVR and pseudophlebitic pattern (PPP) and location of fistula on SWI were determined. Digital subtraction angiography was used as the reference standard. Interobserver agreement for the presence of CVR and PPP and location of DAVF on SWI was evaluated using the kappa statistic. Statistical comparisons between the benign and aggressive DAVFs were performed.

RESULTS

Sensitivity, specificity, positive predictive value, and negative predictive value of SWI for detecting CVR was 73.7%, 85.7%, 87.5%, and 70.6%, respectively. Corresponding values for detecting PPP were 95.2%, 83.3%, 95.2%, and 83.3%, respectively. SWI correctly identified DAVF location in 78.9%. Prevalence rates of CVR and PPP on SWI were significantly higher in aggressive DAVFs than benign ones.

CONCLUSION

SWI exhibited high sensitivity and specificity for detection of CVR, a characteristic used to differentiate benign and aggressive lesions. CVR and PPP on SWI are signs of aggressive DAVFs that guide to perform angiography confirmation and prompt treatment to avoid serious complication.

Relevance of Medullary Vein Sign in Neurosarcoidosis

Background: Central nervous system involvement is uncommon in patients with sarcoidosis. It remains a diagnostic challenge for clinicians, as there is a broad differential diagnosis that matches the presenting neurological signs. Often, the imaging findings also overlap with other disease entities. One understudied finding in patients with neurosarcoidosis is the presence of medullary vein engorgement on SWI imaging, termed the “medullary vein sign”, which has been postulated to be a specific sign for neurosarcoidosis. This study aims to provide an understanding of the diagnostic potential of the medullary vein sign. Methods: Thirty-two patients who presented with neurologic signs concerning for possible neurosarcoidosis were analyzed retrospectively for the presence of the medullary vein sign. Results: Out of these cases, 7 cases of definitive neurosarcoidosis cases were found based on other imaging signs, biopsy and CSF analysis; the remaining were classified into groups as possible (16), probable (5) and (4) cases of other infectious meningoencephalitis including 2 cases of autoimmune encephalitis. Seven patients among all of these cases were found to have the medullary vein sign on imaging, with five cases with confirmed and two cases from possible neurosarcoidosis. The sensitivity of the medullary vein sign in this study was 71.4%, and the specificity was 92.3%. Discussion: The benefits of improving diagnostic criteria for neurosarcoidosis include more rapid diagnosis leading to more prompt treatment, less exposure to potentially harmful antibiotics or antifungals, and less long-term neurological effects. Our results support that the medullary vein sign will potentially fill in the diagnostic gaps that have challenged the timely diagnosis of neurosarcoidosis. Conclusions: Our findings support that the medullary vein sign has a high specificity and should be included in the diagnostic criteria for neurosarcoidosis.

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.

Endovascular treatment for cerebral venous thrombosis: current status, challenges, and opportunities

Cerebral venous thrombosis (CVT) mostly affects young people. So far, endovascular treatment (EVT) has not been shown to be beneficial in CVT, partially because venous EVT tools are not yet fully optimized, and therefore EVT is only used as a rescue treatment in rare cases. Identifying a subgroup of CVT patients that could benefit from EVT is challenging, given the milder course of disease compared with acute ischemic stroke, the paucity of data on prognostic factors (both in the clinical and imaging domain), and the lack of consensus on what constitutes 'technical success' in CVT EVT. In this review, we discuss the major obstacles that are encountered when trying to identify CVT patients that may benefit from EVT, and propose a roadmap that could help to overcome these challenges in the near future.

Intracranial Hemorrhage from Dural Arteriovenous Fistulas: What Can We Find with CT Angiography?

(1) Background: Dural arteriovenous fistulas (DAVF) represent a rare acquired intracranial vascular malformation, with a variety of clinical signs and symptoms, which make their diagnosis difficult. Intracranial hemorrhage is one of the most serious clinical manifestations. In this paper the authors’ goal was to verify the accuracy and utility of contrast-enhanced brain CT angiography (CTA) for the identification and the characterization of dural arteriovenous fistulas (DAVFs) in patients who presented with brain hemorrhage compared to 3D digital subtraction angiography (3D DSA); (2) a retrospective study of 26 patients with DAVFs who presented with intracranial hemorrhage to our institution was performed. The information reviewed included clinical presentation, location and size of hemorrhage, brain CTA and 3D DSA findings; (3) results: 61% (16/26) of DAVFs were identified by CTA. The vast majority of patients were male (69%, 18/26) and the most common presenting symptom was sudden onset headache. All DAVFs had cortical venous drainage and about one-third were associated with a venous varix. The most common location was tentorial (73%, 19/26); (4) conclusions: CTA can represent a valid alternative diagnostic method to 3D DSA for the study of DAVF in the initial and preliminary diagnostic approach, especially in emergency situations. In fact, it represents a fast, inexpensive, non-invasive and above all, easily accessible and available diagnostic technique, unlike DSA or MRI, allowing to provide information necessary for the identification, classification and treatment planning of DAVFs.

Susceptibility-weighted Imaging in Neuroradiology: Practical Imaging Principles, Pearls and Pitfalls

Susceptibility-weighted imaging (SWI) was one of the recent and helpful advancement in magnetic resonance imaging. Its utilization -provided valuable information for the radiologists in multiple fields, including neuroradiology. SWI was able to demonstrate cerebral paramagnetic and diamagnetic substances. Therefore, the applications of this imaging technique were diverse in research and clinical neuroradiology. This article reviewed the basic technical steps, various clinical applications of SWI, and potential limitations. The practicing radiologist needs to be oriented about using SWI and phase images in the right- and left-handed MRI systems to demonstrate different brain pathologies, including neurovascular diseases, traumatic brain injuries, brain tumors, infectious and inflammatory, and neurodegenerative diseases.

Utility of Susceptibility-Weighted Angiography Sequence in the Diagnosis of Ruptured Infectious Aneurysms

In a patient with infective endocarditis (IE), susceptibility-weighted angiography (SWAN) sequence revealed 2 intracranial infectious aneurysms (IIAs) as bright signal lesion, related to the high-velocity arterial flow within the IIAs. In addition, SWAN revealed a convexal subarachnoid hemorrhage-related to distal IIA rupture-as a dark signal. The risk of IIA rupture emphasizes the need for serial imaging follow-up in patients with IE receiving antibiotic therapy after endovascular treatment and after valve surgery. Considering its specific risks, particularly in patients with IE who may be on anticoagulation, digital subtraction angiography is not used routinely in this context. Therefore, SWAN might be an alternative method for selecting patients with IE who need conventional angiography and might be useful for serial follow-up and monitoring after treatment. Future studies should investigate the role of SWAN for the detection of IIAs.

Hypointensity of draining veins on susceptibility-weighted magnetic resonance images might indicate normal venous flow and a lower risk of intracerebral hemorrhage in patients with intracranial arteriovenous shunt(s)

Patients with intracranial arteriovenous shunt(s) have a risk of intracerebral hemorrhage (ICH). We investigated the signal intensity of draining veins on susceptibility-weighted imaging (SWI) and the status of venous drainage shown by digital subtraction angiography (DSA). We then evaluated whether the signal intensity of draining veins on SWI is related to normal venous flow (NVF) and/or ICH. We analyzed SWI and DSA in 10 consecutive patients with intracranial arteriovenous shunt(s). Opacification of draining veins in the normal venous phase by DSA was judged as NVF. We evaluated the relationship between the intensity of draining veins on SWI and the presence of NVF before and after treatment. The relationship between the intensity of draining veins on SWI and the presence of ICH surrounding the draining veins was also evaluated. Of 10 patients with untreated arteriovenous shunt(s), two had arteriovenous malformation and eight had a dural arteriovenous fistula with cortical venous reflux. We analyzed 26 draining veins before treatment. In preoperative analysis, draining veins with hypointensity were significantly more likely to show NVF than were draining veins with isointensity or hyperintensity (45.5% vs. 0.0%, P = 0.007). While 69.2% of the areas surrounding draining veins with isointensity or hyperintensity showed ICH, no veins with hypointensity showed ICH (P = 0.011, odds ratio 0.036; 95% confidence interval 0.0017-0.80). In conclusion, draining veins with hypointensity on SWI may contain NVF, despite arteriovenous shunting. The areas surrounding these veins might have a lower risk of ICH because of less venous hypertension.

Jugular Venous Reflux Can Mimic Posterior Fossa Dural Arteriovenous Fistulas on MRI-MRA

Dural arteriovenous fistulas (DAVFs) are high-flow acquired shunts that can carry high risk of intracranial hemorrhage. Because DAVFs can often be managed by endovascular means, early and accurate diagnosis can markedly improve patient morbidity. Time-of-flight and arterial spin-labeling MRA have increased the diagnostic utility of MRI for DAVF by showing hemodynamic rather than anatomic evidence of shunting. The purpose of this article is to describe the cases of seven patients who had co-localization of arterial spin-labeling signal intensity and time-of-flight flow-related enhancement in the left skull base, resulting in a misdiagnosis of DAVF and a recommendation for catheter angiography by the interpreting radiologist. Benign jugular venous reflux is identified as a common mechanism in each case, and the physiology behind this imaging pitfall is described. An algorithmic diagnostic approach to differentiating physiologic venous reflux from true posterior skull base DAVFs is presented.

Endovascular Treatment of Traumatic Arteriovenous Fistula in Young Adults with Pulsatile Tinnitus

Traumatic arteriovenous fistulas (AVFs) involving the external carotid artery are exceedingly rare in young adults. Since an AVF is the most common life-threatening cause for pulsatile tinnitus (PT), meticulous evaluation and treatment of patients with PT is crucial. Here, we present two traumatic AVF cases treated with coil embolization leading to no residual fistulous connections followed by an immediate and complete resolution of PT. A 20-year-old man developed left ear tinnitus three months after a traumatic brain injury involving the right temporal bone fracture. Cerebral angiography demonstrated an enlarged left middle meningeal artery (MMA) and a fistular point at the posterior branch of the MMA draining to the middle meningeal vein (MMV) and the left pterygoid plexus, suggesting an AVF. Another 18-year-old girl developed left tinnitus, left exophthalmos, and conjunctival injection 6 months after a traffic accident involving no demonstrable abnormal findings in the radiologic exam. Magnetic resonance angiography demonstrated a markedly dilated left MMA draining to the MMV, left cavernous sinus, and left superior ophthalmic vein. In both cases, coil embolization was performed with total obliteration of the fistular point.

Tips and tricks in the diagnosis of intracranial dural arteriovenous fistulas: A pictorial review

Dural arteriovenous fistulas (DAVFs) are complex vascular abnormalities that account for 10-15% of intracranial vascular malformations. DAVFs are typically encountered in middle-aged adults, with a slightly female predominance. The causative factors are still uncertain; however, abnormal local hemodynamics and neoangiogenesis related to dural sinus or venous thrombosis can contribute to DAVF occurrence. The diagnosis is dependent on a high level of clinical suspicion and high-resolution imaging techniques. Computed tomography and/or magnetic resonance imaging aid in the diagnosis, but conventional angiography remains the most accurate method for the complete characterization and classification of DAVFs. The therapeutic approach can be conservative or more aggressive, based on symptom severity, sequelae risk and patient characteristics. This article is a pictorial review of adult intracranial DAVFs that highlights some tips and tricks for recognizing useful red flags in the suspicion of DAVFs.

Susceptibility-Weighted Angiography for the Follow-Up of Brain Arteriovenous Malformations Treated with Stereotactic Radiosurgery

The criterion standard for assessing brain AVM obliteration postradiosurgery is DSA. To explore the value of susceptibility-weighted angiography, we followed 26 patients with brain AVMs treated by radiosurgery using susceptibility-weighted angiography and DSA. Studies were evaluated by 2 independent readers for residual nidi. Susceptibility-weighted angiography demonstrated good intermodality (κ = 0.71) and interobserver (κ = 0.64) agreement, and good sensitivity (85.7%) and specificity (85.7%). Susceptibility-weighted angiography is a useful radiation- and contrast material-free technique to follow-up brain AVM obliteration postradiosurgery.

Relationship between Abnormal Hyperintensity on T2-Weighted Images Around Developmental Venous Anomalies and Magnetic Susceptibility of Their Collecting Veins: In-Vivo Quantitative Susceptibility Mapping Study

Objective

A developmental venous anomaly (DVA) is a vascular malformation of ambiguous clinical significance. We aimed to quantify the susceptibility of draining veins (χ_vein) in DVA and determine its significance with respect to oxygen metabolism using quantitative susceptibility mapping (QSM).

Materials and Methods

Brain magnetic resonance imaging of 27 consecutive patients with incidentally detected DVAs were retrospectively reviewed. Based on the presence of abnormal hyperintensity on T2-weighted images (T2WI) in the brain parenchyma adjacent to DVA, the patients were grouped into edema (E+, n = 9) and non-edema (E−, n = 18) groups. A 3T MR scanner was used to obtain fully flow-compensated gradient echo images for susceptibility-weighted imaging with source images used for QSM processing. The χ_vein was measured semi-automatically using QSM. The normalized χ_vein was also estimated. Clinical and MR measurements were compared between the E+ and E− groups using Student's t-test or Mann-Whitney U test. Correlations between the χ_vein and area of hyperintensity on T2WI and between χ_vein and diameter of the collecting veins were assessed. The correlation coefficient was also calculated using normalized veins.

Results

The DVAs of the E+ group had significantly higher χ_vein (196.5 ± 27.9 vs. 167.7 ± 33.6, p = 0.036) and larger diameter of the draining veins (p = 0.006), and patients were older (p = 0.006) than those in the E− group. The χ_vein was also linearly correlated with the hyperintense area on T2WI (r = 0.633, 95% confidence interval 0.333–0.817, p < 0.001).

Conclusion

DVAs with abnormal hyperintensity on T2WI have higher susceptibility values for draining veins, indicating an increased oxygen extraction fraction that might be associated with venous congestion.

Susceptibility-Weighted Imaging of Deep Venous Congestion in Petroclival Meningioma

BACKGROUND

Protecting the venous drainage route during surgery in cases of petroclival meningioma (PCM) is important. Identifying venous congestion preoperatively can be valuable in reducing the risks associated with venous congestion during surgery. In this study, we examined the utility of susceptibility-weighted imaging (SWI) in identifying the presence of venous congestion in PCM cases preoperatively and identified the factors associated with it.

METHODS

We retrospectively examined 24 patients who had undergone surgery for primary PCM. The areas of the basal and internal cerebral veins on the affected and unaffected sides, obtained using SWI, were compared to identify venous congestion. We further examined the association between multiple candidate factors that are thought to be related to venous congestion and venous congestion using statistical analyses.

RESULTS

SWI could successfully identify venous congestion in 11 of 24 PCM cases. Among the 12 factors examined, those associated with venous congestion were an extension of the tumor, over the midline or upward, which is known to disturb the venous flow at the brainstem surface; anastomosis of the superficial cerebral vein (i.e., bypass route for venous congestion); and a high ABC Surgical Risk Scale score, an indicator of postoperative neurologic deterioration.

CONCLUSIONS

We showed that SWI is useful for evaluating venous congestion in PCM cases preoperatively and for identifying factors reflecting the risk of venous congestion. Taken together, our findings provide a multimodal strategy for the preoperative prediction of venous congestion, which could facilitate the treatment of PCM.

Contralateral extensive cerebral hemorrhagic venous infarction caused by retrograde venous reflux into the opposite basal vein of Rosenthal in posttraumatic carotid-cavernous fistula: A case report and literature review

We describe a patient with traumatic carotid-cavernous fistula (CCF), subsequently developing contralateral extensive hemorrhagic venous infarction from retrograde venous reflux into the opposite basal vein of Rosenthal. A 54-year-old woman was involved in a motor vehicle accident and sustained severe traumatic brain injury. Two months later, she developed bilateral proptosis and audible bruit. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the brain demonstrated the right direct CCF. Fluid-attenuated inversion recovery (FLAIR) images showed a small hyperintense area at the left basal ganglia. Ten days later, she developed right-sided grade 2/5 hemiparesis, facial upper motor neuron weakness, and cognitive impairment. Follow-up MRI showed significant progression of hyperintensities involving the left-sided centrum semiovale, basal ganglia, thalamus, midbrain, pons, cerebellum, basal frontal, temporal lobes, especially subcortical white matter on FLAIR images, and multiple hypointense foci of hemorrhagic component on T2*-weighted gradient-echo images, representing hemorrhagic venous infarction. While waiting for embolization, she rapidly developed right hemiplegia and aphasia, and became somnolent. Under general anesthesia, emergency endovascular treatment was performed successfully to obliterate the fistula without surgical intervention. Five months after endovascular treatment, MRI and MRA confirmed no residual fistula and revealed nearly complete resolution of abnormal increased signal intensity. In the present case, the factors related to the presence of this rare condition were absence of the ipsilateral basal vein of Rosenthal (BVR), occlusion of posterior segment of the contralateral superior petrosal sinus, and a developed uncal vein with hypoplastic second and third segments of the contralateral BVR.

Engorged medullary vein on CT angiography in patients with dural arteriovenous fistula: prevalence, types, and comparison between regional and extensive types

BACKGROUND AND PURPOSE

Engorged medullary vein (EMV) in patients with intracranial dural arteriovenous fistula (DAVF) suggests venous congestion. The aim of this study is to investigate its prevalence, pattern, and correlation with clinical findings.

MATERIALS AND METHODS

CT angiography (CTA) raw data of DAVF were used for multiplanar reconstruction and then analyzed for the presence and pattern of EMV, which is defined as a dilated vein in the cerebral white matter. Patients with EMV were divided into two groups: regional and extensive. Regional type is defined as EMV limited to one cerebral hemisphere or cerebellum without evidence of subcortical calcification. Extensive type is defined as EMV involvement of more than one cerebral hemisphere or both the cerebrum and cerebellum. Descriptive analysis of clinical information, DAVF characteristics, and other imaging findings was conducted. Clinical information, including demographic data, clinical presentation, and hemorrhage, were correlated with both types of EMV.

RESULTS

Among 192 eligible patients with DAVF, 71 (37%) had EMV. Patients with EMV were older (63 years vs 56 years, P=0.02), with DAVF more often at the transverse and sigmoid sinus (P<0.001), and more often presented with aggressive symptoms (59% vs 34%, P=0.02) than non-EMV patients, but there was no difference in the presentation of hemorrhage (15% vs 16%, P=0.99). Patients with regional EMV had a higher proportion of hemorrhage than those with the extensive type (24% vs 0%, P=0.006).

CONCLUSIONS

EMV in patients with DAVF is associated with an aggressive manifestation. Regional type EMV is associated with a higher risk of a hemorrhagic presentation.

Diagnostic accuracy of CTA and MRI/MRA in the evaluation of the cortical venous reflux in the intracranial dural arteriovenous fistula DAVF

PURPOSE

Computed tomography angiography (CTA) and magnetic resonance imaging/angiography (MRI/MRA) are used for the diagnosis of intracranial dural arteriovenous fistulas (DAVFs). The purpose of this study was to compare the diagnostic accuracy of CTA and magnetic resonance imaging/angiography (MRI/MRA) for detection of cortical venous reflux (CVR) in intracranial DAVFs.

METHODS

The records of patients with angiography-confirmed intracranial DAVFs who also received CTA and MRI/MRA from January 2008 to July 2016 were reviewed. CTA and MRI/MRA were reviewed for signs of CVR, and the diagnostic accuracy of individual signs was evaluated by receiver operating curve (ROC) analysis.

RESULTS

A total 108 patients were included in this study. CTA signs of CVR included abnormal dilatation, early enhancement, and the presence of a medullary or pial vein. MRI/MRA signs of CVR included abnormal dilatation, early enhancement, flow-related enhancement, flow void, and medullary or pial venous collaterals. The sensitivity of individual CTA signs ranged from 62 to 96%, and specificities from 79 to 94%. The sensitivities of individual MRI/MRA signs ranged from 58 to 83%, and specificities from 77 to 93%. The area under ROC curve (AUC) of CTA and MRI/MRA were 0.91 and 0.87, respectively (P = 0.04 in direct comparison). In subgroup analysis, CTA had better diagnostic accuracy for higher grade disease (P = 0.05) and non-aggressive manifestation (P = 0.04).

CONCLUSIONS

Both CTA and MRI/MRA have good diagnostic accuracy for detection of CVR in patients with intracranial DAVFs. There is modest evidence that CTA is better than MRI/MRA.

Dural arteriovenous fistula disguised as cerebral venous sinus thrombosis

Dural arteriovenous fistulas (DAVFs) are direct communications between the intracranial arterial and venous systems without an intervening nidus. Clinicians sometimes fail to give a correct diagnosis of DAVF. Given the similarity of their clinical and magnetic resonance imaging (MRI) manifestations, diagnostic confusion may arise between DAVF and cerebral venous sinus thrombosis (CVST) (Simon et al., 2009). The clinical management of DAVFs differs from that of CVST (Ma et al., 2015; Yang et al., 2015). Anticoagulation therapy is restricted in some cases of DAVFs, especially when they are associated with retrograde venous flow, due to the increased risk of hemorrhage. Here we present a case of a DAVF patient who had been initially misdiagnosed as CVST. We summarize the reasons for misdiagnosis and give some recommendations to address this problem.

Susceptibility-weighted Imaging in Neurovascular Disease

Susceptibility-weighted imaging (SWI) has become an important imaging sequence in the evaluation of patients with neurovascular disease. In this review, we provide a general overview of the physics of SWI and describe how image contrast is produced with this technique. We provide a general approach and differential diagnosis for 2 commonly encountered radiographic patterns seen with SWI in neurovascular disease. Finally, we discuss specific neurovascular applications of SWI, including its application in acute stroke, vascular malformations, venous thrombosis, and evaluation of cerebral microbleeds.

Intracranial Arteriovenous Shunting: Detection with Arterial Spin-Labeling and Susceptibility-Weighted Imaging Combined

BACKGROUND AND PURPOSE

Arterial spin-labeling and susceptibility-weighted imaging are 2 MR imaging techniques that do not require gadolinium. The study aimed to assess the accuracy of arterial spin-labeling and SWI combined for detecting intracranial arteriovenous shunting in comparison with conventional MR imaging.

MATERIALS AND METHODS

Ninety-two consecutive patients with a known (n = 24) or suspected arteriovenous shunting (n = 68) underwent digital subtraction angiography and brain MR imaging, including arterial spin-labeling/SWI and conventional angiographic MR imaging (3D TOF, 4D time-resolved, and 3D contrast-enhanced MRA). Arterial spin-labeling/SWI and conventional MR imaging were reviewed separately in a randomized order by 2 blinded radiologists who judged the presence or absence of arteriovenous shunting. The accuracy of arterial spin-labeling/SWI for the detection of arteriovenous shunting was calculated by using the area under receiver operating curve with DSA as reference standard. κ coefficients were computed to determine interobserver and intermodality agreement.

RESULTS

Of the 92 patients, DSA showed arteriovenous shunting in 63 (arteriovenous malformation in 53 and dural arteriovenous fistula in 10). Interobserver agreement was excellent (κ =0.83-0.95). In 5 patients, arterial spin-labeling/SWI correctly detected arteriovenous shunting, while the conventional angiographic MR imaging did not. Compared with conventional MR imaging, arterial spin-labeling/SWI was significantly more sensitive (0.98 versus 0.90, P = .04) and equally specific (0.97) and showed significantly higher agreement with DSA (κ = 0.95 versus 0.84, P = .01) and higher area under the receiver operating curve (0.97 versus 0.93, P = .02).

CONCLUSIONS

Our study showed that the combined use of arterial spin-labeling and SWI may be an alternative to contrast-enhanced MRA for the detection of intracranial arteriovenous shunting.

Diagnosis and management of intracranial dural arteriovenous fistulas

Dural arteriovenous fistula (DAVF) is a rare type of acquired intracranial vascular malformation. Recent progress in neuroimaging technology, such as advanced MRI and CT, provides non-invasive methods to accurately diagnose DAVF, including evaluation of the hemodynamics of the drainage veins. The clinical manifestations of DAVFs vary widely and depend on the location and venous drainage pattern of arteriovenous shunting. Patients with high grade DAVFs having cortical venous reflux should receive aggressive treatment to prevent the occurrence of intracranial hemorrhage and other neurological deficits related to venous congestion. Intra-arterial or intravenous endovascular embolization remains the primary therapy for high grade DAVF, while open surgery and stereotactic radiosurgery can serve as alternative treatment options. Early and accurate diagnosis with appropriate treatment is the goal for clinical management of DAVFs to reduce symptoms and prevent the development of venous congestion and stroke.

Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives

Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.

CT and MR imaging of non-cavernous cranial dural arteriovenous fistulas: Findings associated with cortical venous reflux

PURPOSE

To compare the conventional CT and MR findings of DAVFs in relation to the venous drainage pattern on digital subtraction angiography (DSA).

MATERIALS AND METHODS

Cross-sectional imaging findings (CT and/or MR) in 92 patients were compared to the presence of cortical venous reflux (CVR) on DSA.

RESULTS

Imaging features significantly more prevalent in patients with CVR included: abnormally dilated and tortuous leptomeningeal vessels (92% vs. 4%, p<0.001) or medullary vessels (69% vs. 0%, p<0.001), venous ectasias (45% vs. 0%, p<0.001) and focal vasogenic edema (38% vs. 0%, p<0.001). The following findings trended towards association but did not reach the p value established following Bonferroni correction: dilated external carotid artery branches (71% vs. 38%, p=0.005), cluster of vessels surrounding dural venous sinus (50% vs. 19%, p=0.009), presence of hemorrhage (33 vs. 12%, p=0.040), and parenchymal enhancement (21% vs. 0%, p=0.030).

CONCLUSION

In the appropriate clinical setting, recognition of ancillary signs presumably related to venous arterialization and congestion as well as arterial feeder hypertrophy should prompt DSA confirmation to identify DAVFs associated with CVR.

Value of DSA in the diagnostic workup of pulsatile tinnitus

Objectives

Pulsatile tinnitus (PT) is a rare complaint, but can be a symptom of life-threatening disease. It is often caused by vascular pathologies, e.g. dural arteriovenous fistula (dAVF), arteriovenous malformation (AVM) or vascularized tumors. The current diagnostic pathway includes clinical examination, cranial MRI and additional DSA. The aim of this study was to evaluate the diagnostic impact of DSA in the diagnostic workup of patients with PT in comparison to MRI alone.

Methods

Retrospectively, 54 consecutive patients with pulsatile tinnitus were evaluated. All patients had a diagnostic workup including cranial MRI and DSA. MRI examinations were blinded to the results of DSA and retrospectively analyzed in consensus by two experienced neuroradiologists. The MR-examinations were evaluated for each performed sequence separately: time-of-flight-angiography, ce-MRA, T2, ce-T1-sequence and ce-T1-sequence with fat saturation.

Results

37 of the 54 patients revealed a pathology explaining PT on MRI, which was detected by the readers in 100% and proofed by means of DSA. 24 dAVF, four paraganglioma, two AVM and seven more pathologies were described. All patients without pathology on MRI did also not show any pathology in DSA.

Conclusions

MR imaging is sufficient to exclude pathology in patients with pulsatile tinnitus.

Susceptibility-weighted imaging in carotido-cavernous fistulas. A case control study

This study determined the utility and accuracy of susceptibility-weighted MRI (SWI) for the detection of carotid cavernous fistulas. We retrospectively compared SWI images in nine patients (Group 1, case group) of DSA-proved carotid cavernous fistula (CCF) and 19 DSA negative cases for CCF as a control group (Group 2). Group 1 was again sub-grouped into direct and indirect types. Using uniform region-of-interest measurements, signal intensity within the superior ophthalmic vein (SOV) and the superior sagittal sinus (SSS) were measured on magnitude images of SWI. The SOV/SSS signal intensity ratio was calculated in each case and the mean values of the two groups were compared. Eleven SOV/SSS signal intensity ratios in Group 1 (7 unilateral and two bilateral CCF), 38 in Group 2 (both sides in 19 control subjects) were included. Median ± interquartile range of SOV/SSS ratios for Group 1, Group 2, indirect and direct type CCFs were 1.07 ± 0.43, 0.39 ± 0.23, 0.83 ±0.29, 1.4 ±0.38 respectively. Mann-Whitney test between Groups 1 and 2 was statistically significant with P<0.0001. All cases and controls were reliably distinguished with SOV/SSS signal intensity ratio of 0.64 as cut-off. Direct CCF cases had consistently higher ratios than indirect CCF. SWI was highly sensitive for detection and differentiation of both direct and indirect CCF. Only one case of corticovenous reflux was missed by SWI. SWI is useful for detection of CCF and to differentiate between direct and indirect CCF.

The use of susceptibility-weighted imaging as an indicator of retrograde leptomeningeal venous drainage and venous congestion with dural arteriovenous fistula: diagnosis and follow-up after treatment

BACKGROUND

Retrograde leptomeningeal venous drainage (RLVD) in dural arteriovenous fistulas (DAVFs) is associated with intracerebral hemorrhage and nonhemorrhagic neurological deficits or death. Angiographic evidence of RLVD is a definite indication for treatment, but less invasive methods of identifying RLVD are required.

OBJECTIVE

To evaluate the efficacy of susceptibility-weighted magnetic resonance imaging (SWI) in detecting RLVD in DAVFs.

METHODS

We retrospectively identified 17 DAVF patients who had angiographic evidence of RLVD and received treatment. Conventional angiography and SWI were assessed at pretreatment and posttreatment time points. The presence of RLVD on SWI was defined as cortical venous hyperintensity, and the presence of venous congestion on SWI venograms was defined as increased caliber of cortical or medullary veins.

RESULTS

Cortical venous hyperintensity was identified in pretreatment SWI of 15 patients. Cortical venous hyperintensity was absent in early posttreatment SWI, consistent with the absence of RLVD in posttreatment angiography, in all but one of these patients. In 2 patients, cortical venous hyperintensity was identified during follow-up, indicating the recurrence of RLVD. Cortical venous hyperintensity was not identified in the pretreatment SWI of 2 patients despite angiographic evidence of RLVD. Venous congestion was identified in pretreatment SWI venograms of 11 patients and had an appearance similar to that identified from angiography. Venous congestive signs improved over the follow-up period.

CONCLUSION

The presence of SWI hyperintensity within the venous structure could be a useful indicator of RLVD in DAVF patients. Thus, SWI offers a noninvasive alternative to angiography for the identification of RLVD in pretreated and posttreated DAVF patients.

Susceptibility-weighted angiography for the detection of high-flow intracranial vascular lesions: preliminary study

OBJECTIVES

Susceptibility-weighted magnetic resonance imaging (MRI) sequences may demonstrate various signal intensities of draining veins in cases of high-flow vascular malformation (HFVM), including arteriovenous malformation (AVM) and dural arteriovenous fistula (dAVF). Our objective was to evaluate susceptibility-weighted angiography (SWAN) for the detection of HFVM.

METHODS

Fifty-eight consecutive patients with a suspected intracranial vascular malformation were explored with SWAN and post-contrast MRI sequences at 3 T. The diagnosis of slow-flow vascular malformation (SFVM), including developmental venous anomaly (DVA) or brain capillary telangiectasia (BCT), was based on MRI. Patients with suspected HFVM underwent digital subtraction angiography (DSA). SWAN images were analysed by three blinded readers according to a three-point scale of the venous signal.

RESULTS

Thirty-one patients presented 35 SFVM (26 DVA and 9 BCT) that systematically appeared hypointense on SWAN images. In patients with atypical MRI findings, DSA revealed one patient with an atypical DVA and 26 patients with HFVM (22 AVM and 4 dAVF). SWAN revealed at least one venous hyperintensity in all patients with HFVM. Agreement between readers was excellent.

CONCLUSIONS

SWAN appears reliable for characterising blood flow dynamics in brain veins. In clinical practice, SWAN can routinely rule out HFVM in patients with atypical brain veins.

Susceptibility-weighted imaging: a new tool in the diagnosis and evaluation of abnormalities of the vein of Galen in children

We retrospectively identified 9 consecutive children, 3 males and 6 females (age 5.2 ± 6.3 years, range 1 day to 18 years), with known or suspected AVGs who underwent MR imaging, including SWI, at our institution between January 2007 and March 2011. On the SWI sequence, arterialized blood flow was considered to be present in the vein of Galen or its tributaries when these showed abnormal signal hyperintensity from arteriovenous shunting. SWI findings were correlated with findings from DSA studies or findings from time-of-flight or contrast-enhanced MR angiography sequences. SWI was found to accurately differentiate between high-flow and low-flow AVGs and was also useful in characterizing the arterial supply and venous drainage patterns associated with high-flow AVGs.