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

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.

Dural Arteriovenous Fistula

Dural arteriovenous fistulas are rare cerebrovascular lesions arising from abnormal connections between an artery and a vein. Though rare, high-grade aggressive lesions can cause hemorrhagic events and non-hemorrhagic neurologic deficits if left untreated. Treatment options vary based on angioarchitecture, location, and patient characteristics and range from conservative observation to palliative treatment, radiosurgery, endovascular embolization, and open surgery. The main goal of treatment is to obliterate flow through the abnormal connection and prevent further arterial flow to the venous system.

A novel angiographic method to estimate arterial blood flow rates using contrast reflux: Effect of injection parameters

BACKGROUND

Contrast reflux, which is the retrograde movement of contrast against flow direction, is commonly observed during angiography. Despite a vast body of literature on angiography, the hemodynamic factors affecting contrast reflux have not been studied. Numerous methods have been developed to extract flow from angiography, but the reliability of these methods is not yet sufficient to be of routine clinical use.

PURPOSE

To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length.

MATERIALS AND METHODS

Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico-cerebral vasculature. A total of 194 high-speed angiograms were acquired under varying "blood" flow rates and injection conditions (catheter size, injection rate, and injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter-tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit-time method and compared to measured flow rates.

RESULTS

Contrast reflux lengths were significantly affected by contrast injection rate (p < 0.0001), baseline blood flow rate (p = 0.0004), and catheter size (p = 0.04), but not by contrast injection time (p = 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R²  = 0.6-0.99). When considering the entire dataset in unison, flow estimation errors with the reflux-length method (39% ± 33%) were significantly higher (p = 0.003) than the transit-time method (33% ± 36%). However, when subgrouped by catheter, the error with the reflux-length method was substantially reduced and was significantly lower (14% ± 14%, p < 0.0001) than the transit-time method.

CONCLUSION

Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux.

Dural arteriovenous fistulas misdiagnosed as intracranial neoplasms: illustrative case

BACKGROUND

Dural arteriovenous fistulas (dAVF) may induce imaging findings attributable to various disease entities including malignant neoplasms. In these cases, diagnosis and adequate treatment are often delayed and patients may be exposed to spurious treatments in addition to the risks inherent to an untreated dAVF with cortical venous drainage.

OBSERVATIONS

The authors report a case of a patient referred for surgical treatment of a supratentorial high-grade glioma. Thorough review of imaging data challenged the initial radiological diagnosis and led to proper angiographic workup. As a result, a high-grade dAVF was confirmed and successfully embolized. In addition to this case, we provide an extensive literature review on dAVF initially diagnosed as cerebral neoplasms, including clinical, imaging and follow-up data.

LESSONS

The literature provides diagnostic criteria for dAVF on magnetic resonance imaging; however, those criteria may be only partly applicable in many cases. Misdiagnosis of a neoplasm due to dAVF has been reported but remains rare, especially in supratentorial lesions. Digital subtraction angiography should be pursued to rule out an underlying vascular pathology if any doubt. This may prevent unnecessary interventions such as biopsies, pharmacological treatment and a delay in dAVF treatment, given its associated risk of hemorrhage and nonhemorrhagic neurological deficits.

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.

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.

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.