Components Of Arteriovenous Malformations Research Articles

Does the Diffuseness of the Nidus Affect the Outcome of Stereotactic Radiosurgery in Patients with Unruptured Cerebral Arteriovenous Malformations?

Background: We proposed an algorithm to automate the components within the identification of components within the nidus of cerebral arteriovenous malformations (AVMs) which may be used to analyze the relationship between its diffuseness and treatment outcomes following stereotactic radiosurgery (SRS). Objectives: to determine the impact of the diffuseness of the AVM nidus on SRS outcomes. Methods: This study conducted regular follow-ups of 209 patients with unruptured AVMs who underwent SRS. The diffuseness of the AVM nidus was estimated by quantifying the proportions of vascular nidal component, brain parenchyma, and cerebrospinal fluid in T2-weighted MRIs. We used Cox regression analysis to characterize the association between nidal diffuseness and treatment outcomes in terms of obliteration rate and radiation-induced change (RICs) rate following SRS. Results: The median AVM volume was 20.7 cm³. The median duration of imaging follow-up was 51 months after SRS. The overall AVM obliteration rate was 68.4%. RICs were identified in 156 of the 209 patients (74.6%). The median proportions of the nidus of AVM and brain parenchyma components within the prescription isodose range were 30.2 and 52.2%, respectively. Cox regression multivariate analysis revealed that the only factor associated with AVM obliteration rate after SRS was AVM volume. However, a larger AVM volume (>20 mL) and a larger proportion of brain parenchyma (>50%) within the prescription isodose range were both correlated with a higher RIC rate following SRS. Conclusions: The diffuseness of the nidus indeed appears to affect the RIC rate following SRS in patients with unruptured AVMs.

Vessel-selective 4D-MR angiography using super-selective pseudo-continuous arterial spin labeling may be a useful tool for assessing brain AVM hemodynamics.

To evaluate the usefulness of 4D-MR angiography based on super-selective pseudo-continuous ASL combined with keyhole and view-sharing (4D-S-PACK) for vessel-selective visualization and to examine the ability of this technique to visualize brain arteriovenous malformations (AVMs). In this retrospective study, 15 patients (ten men and five women, mean age 44.0 ± 16.9years) with brain AVMs were enrolled. All patients were imaged with 4D-PACK (non-selective), 4D-S-PACK, and digital subtraction angiography (DSA). Observers evaluated vessel selectivity, identification of feeding arteries and venous drainage patterns, visualization scores, and contrast-to-noise ratio (CNR) for each AVM component. Measurements were compared between the MR methods. Vessel selectivity was graded 4 in 43/45 (95.6%, observer 1) and 42/45 (93.3%, observer 2) territories and graded 3 in two (observer 1) and three (observer 2) territories. The sensitivity and specificity for identification of feeding arteries for both observers was 88.9% and 100% on 4D-PACK, and 100% and 100% on 4D-S-PACK, respectively. For venous drainage, the sensitivity and specificity was 100% on both methods for observer 1. The sensitivity and specificity for observer 2 was 94.4% and 83.3% on 4D-PACK, and 94.4% and 91.7% on 4D-S-PACK, respectively. The CNRs at the timepoint of 1600ms were slightly lower in 4D-S-PACK than in 4D-PACK for all AVM components (Feeding artery, p = .02; nidus, p = .001; and draining artery, p = .02). The visualization scores for both observers were not significantly different between 4D-PACK and 4D-S-PACK for all components. 4D-S-PACK could be a useful non-invasive clinical tool for assessing hemodynamics in brain AVMs. • The 4D-MR angiography based on super-selective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK) enabled excellent vessel selectivity. • The 4D-S-PACK enabled the perfect identification of feeding arteries of brain arteriovenous malformation (AVM). • 4D-S-PACK could be a non-invasive clinical tool for assessing hemodynamics in brain AVMs.

Application of Indocyanine Green During Arteriovenous Malformation Surgery: Evidence, Techniques, and Practical Pearls.

Indocyanine green (ICG) is a fluorescent molecule that enables visualization of hemodynamic flow through blood vessels. The first description of its application to the resection of arteriovenous malformations (AVMs) did not occur until 2007. Since then, industry leaders have rapidly integrated this optical technology into the intraoperative microscope, and the use of ICG videoangiography (VA) has since become routine in AVM surgery among some academic centers. A number of case series have been published since the introduction of ICG VA to AVM neurosurgery. These early reports with small sample sizes were largely qualitative, assigning to the technology “usefulness” and “benefit” scores as perceived by the operators. This lack of objectivity prompted the development of FLOW 800 software, a proprietary technology of Carl Zeiss Meditec AG (Oberkochen, Germany) that can quantify relative fluorescence intensity under the microscope to generate color maps and intensity curves for ad hoc and post hoc analyses, respectively. However, subsequent case series have done little to quantify the effect of ICG VA on outcomes. The available literature predominately concludes that ICG VA, although intuitive to deploy and interpret, is limited by its dependence on direct illumination and visualization. The subcortical components of AVMs represent a natural challenge to ICG-based flow analysis, and the scope of ICG VA has therefore been limited to AVMs with a high proportion of superficial angioarchitecture. As a result, digital subtraction angiography has remained the gold standard for confirming AVM obliteration. In this review, we provide an overview of the existing literature on ICG VA in AVM resection surgery. In addition, we describe our own experiences with ICG VA and AVMs and offer the senior author's surgical pearls for optimizing the marriage of fluorescence flow technology and AVM resection surgery.

Hemodynamic quantification in brain arteriovenous malformations with time-resolved spin-labeled magnetic resonance angiography.

Unenhanced time-resolved spin-labeled magnetic resonance angiography enables hemodynamic quantification in arteriovenous malformations (AVMs). Our purpose was to identify quantitative parameters that discriminate among different AVM components and to relate hemodynamic patterns with rupture risk. Sixteen patients presenting with AVMs (7 women, 9 men; mean age 37.1±15.9 years) were assigned to the high rupture risk or low rupture risk group according to anatomic AVM characteristics and rupture history. High temporal resolution (<70 ms) unenhanced time-resolved spin-labeled magnetic resonance angiography was performed on a 3-T MR system. After dedicated image processing, hemodynamic quantitative parameters were computed. T tests were used to compare quantitative parameters among AVM components, between the high rupture risk and low rupture risk groups, and between the hemorrhagic and nonhemorrhagic groups. Among the quantitative parameters, time-to-peak (P<0.001) and maximum outflow gradient (P=0.01) allowed discriminating various intranidal flow patterns with significantly different values between feeding arteries and draining veins. With 9 AVMs classified into the high rupture risk group (whose 6 were hemorrhagic) and 7 into the low rupture risk group, the observed venous-to-arterial time-to-peak ratio was significantly lower in the high rupture risk (P=0.003) and hemorrhagic (P=0.001) groups. Unenhanced time-resolved spin-labeled magnetic resonance angiography allows AVM-specific combined anatomic and quantitative analysis of AVM hemodynamics.

Susceptibility-weighted imaging in the evaluation of brain arteriovenous malformations

Digital subtraction angiography (DSA) remains the gold standard in the evaluation of arteriovenous malformations (AVMs). Susceptibility-weighted imaging (SWI), a relatively new magnetic resonance imaging (MRI) technique, exploits the magnetic susceptibility differences of various tissues, such as blood, iron and calcification. Earlier studies have shown that the magnitude and phase information of SWI offers improved sensitivity, revealing low-flow vascular malformations that are invisible on conventional gradient-echo (GRE) sequences. To evaluate the imaging appearance of AVMs on SWI. In this retrospective study, the appearance of the various components (feeding artery, nidus, and draining veins) of AVMs on the phase, magnitude, and minimal intensity projection (minIP) images of SWI were analyzed in 14 patients with AVM and compared with conventional sequences. Detection and delineation of various components of AVMs was best achieved in the magnitude images. Although minIP was most effective in detecting hemorrhage and calcification, it was the magnitude image that could separate the hemorrhagic and calcified component in the nidus from the remaining nidus. The minIP was less effective in detecting the AVM components, especially nidus and draining vein, whereas conspicuity was poor with the phase images. The magnitude images of the SWI help in differentiating the different components of AVM and also helps in differentiating nidus from hemorrhage and calcification.

Clinical utility of susceptibility-weighted imaging in vascular diseases of the brain

Susceptibility-weighted imaging (SWI) is a rapidly evolving technique that utilizes both the magnitude and phase information to obtain valuable information about susceptibility changes between tissues. SWI is very sensitive to the paramagnetic effects of deoxyhemoglobin. SWI plays an important role in the diagnostic evaluation and management of acute stroke. In addition, it also plays an important role in the imaging of patients with chronic arterial occlusion and in understanding the effects of chronic infarction, like incomplete infarction and cortical laminar necrosis. The hemodynamic status and oxygen extraction fraction can also be evaluated. SWI is useful in evaluating cerebral venous sinus thrombosis by demonstrating the hemorrhagic venous infarction and thrombus in the sinus and the cortical veins, as well as secondary phenomena like venous stasis in the form of engorged cortical and transmedullary veins and collateral slow flow. Low-flow vascular malformations that are not visualized well on conventional sequences are depicted in exquisite detail along with the venous components on SWI. SWI is used for evaluating cavernomas, developmental venous anomalies, telangiactasias, dural arteriovenous fistulas and the various components of arteriovenous malformations. It has also evolved as a noninvasive technique for evaluating various anomalies of the venous system without administering contrast. Vasculopathies and vasculitis are associated with cerebral microbleeds which are detected on SWI. On the basis of the additional information provided by SWI, it can be included in the routine brain imaging protocol.

MR-angiogram-added surface anatomy scanning of superficial cerebral arteriovenous malformations.

Our purpose was to evaluate the utility of surface anatomy scanning (SAS) of the brain with superimposition of MR angiograms in the diagnosis and presurgical planning of superficial cerebral arteriovenous malformations (AVMs). We performed SAS in 15 patients with superficial cerebral AVMs. Two-dimensional phase-contrast MR angiograms were then obtained in the same section and superimposed on the SAS images. The images were assessed regarding the visualization of each AVM component using a four-point grading scale (3=excellent to 0=poor). In 13 of the patients, the assessment was made comparing with conventional angiograms. The images were also compared with the surgical findings in 5 patients. The added images agreed well with the angiographic findings and demonstrated the relationships between the AVM components and the adjacent brain surface. The average scores of the feeder(s), nidus, and drainer(s) were 2.27, 2.33, and 2.67, respectively. The surgical findings also correlated well with the added images. Our technique can noninvasively demonstrate superficial AVMs along with the brain surface and provide information useful for planning surgery.

Expression of smooth muscle proteins in cavernous and arteriovenous malformations.

Cavernous malformations (CVMs) and arteriovenous malformations (AVMs) were immunostained for three smooth muscle cell (SMC)-specific protein markers (smooth muscle alpha-actin, SM1 and SM2). Smooth muscle alpha-actin, a widely used marker of SMCs, is reportedly one of the earliest proteins expressed during differentiation of SMCs and expressed in some kinds of mesoderm-derived cells. In contrast, SM1, an isoform of myosin heavy chain (MHC), is detected only in SMCs. SM2 is another MHC isoform and expressed in the contractile phenotype of SMC. All 14 intraaxial CVMs were positive for smooth muscle alpha-actin, but SM1 was detected in only three of them and SM2 was not found. Their staining pattern resembled that of normal intraparenchymal and pial veins. All 15 cerebral AVMs and 5 out of 6 extraaxial CVMs from the cavernous sinus, orbit and scalp were positive for all three markers, as were the normal cerebral arteries. The venous components of AVMs, as well as the arterial components, expressed SM2, and were different from normal veins in the brain and intraaxial CVMs. This study shows that the histological analysis using the three markers for SMC is useful to differentiate intraaxial CVM from AVM and extraaxial CVMs.