Spinal arteriovenous malformation: MR imaging

Ten patients with spinal arteriovenous malformations (AVMs) were examined with high-field-strength (1.5-T) magnetic resonance (MR) imaging and a surface coil (eight patients) or head coil (two patients). Four AVMs were intramedullary, and six were extramedullary. There was one case of Foix-Alajouanine disease (subacute necrotizing myelitis; thrombosed AVM). Three important pathologic findings--myelomalacia, total thrombosis, and wall thickening of the draining vein--were clearly demonstrated at MR imaging and confirmed at autopsy. A flow-sensitive sequence was valuable in the depiction of one intramedullary AVM as hyperintense, the postoperative evaluation of AVM, and the differentiation of nidus from old intramedullary hematoma. In other AVMs, cord edema, periradicular hematoma, and reversible changes of cord scalloping after surgery were demonstrated. MR imaging demonstrated various pathologic changes of the spinal cord that could not be detected with any other imaging method.     

Intracerebral arteriovenous malformations: evaluation with selective MR angiography and venography

Magnetic resonance (MR) angiography and spin-echo methods were used to evaluate intracerebral arteriovenous malformations (AVMs) in 10 patients. Spin-echo images obtained with flow presaturation demonstrated the nidus of the AVM in all cases, but it was difficult to determine feeding vessels. These vessels were directly visualized with three-dimensional MR angiography; their presence could be indirectly determined by means of selective presaturation of individual vessels, which resulted in a marked decrease in signal within the portion of the AVM supplied by that vessel. Vascular supplies from the internal carotid artery and anterior, middle, or posterior cerebral arteries were detected in all cases, but in three large malformations it was not possible to demonstrate small feeding vessels. MR angiograms were also helpful for further defining the nidus. The combination of MR angiographic and spin-echo methods provides information useful for therapeutic planning not provided by either technique alone.     

Size determination of supratentorial arteriovenous malformations by MR,CT and angio

Summary Twenty patients with high-flow supratentorial arteriovenous malformations (AVMs) were studied by magnetic resonance imaging (MR), computed tomography (CT), and selective cerebral angiography. The size of the malformation measured on MR was found, in general, to be smaller than the size determined from angiographic films. This discrepancy increased as the size of the AVM increased. AVM size on CT and angiography was found to be essentially equivalent. The reason for these differences between MR and CT or angiography was the ability to separate out the draining veins by MR, whereas this was difficult on projection films and contrast enhanced CT. Calcification was more easily detected by CT than by MR. MR better detected hemorrhage, which could be mistaken for old infarction on CT. Foci of cystic change within the nidus of the AVM were equally evident on MR and CT. Due to its sensitivity in discriminating between AVM nidus and adjacent draining veins and MR's ability to show the AVM in three planes, MR appeared to be more accurate in defining the AVM nidus than either CT or cerebral angiography. Such accurate delineation is crucial in patients prior to stereotactic radiosurgery.     

MR imaging in the management of supratentorial intracranial AVMs

The MR images, CT scans, and angiograms of 15 consecutive patients with intracranial, supratentorial arteriovenous malformations (AVMs) were studied retrospectively. The three imaging techniques were evaluated separately to assess their utility in defining the size, characteristics, and location of the AVM nidus, its arterial supply, and venous drainage. The studies were also evaluated for their ability to show associated parenchymal abnormalities, the presence of mass effect, and changes occurring after embolization. MR was superior to both CT and angiography in showing the exact anatomic relationships of the nidus, feeding arteries, and draining veins, as well as in demonstrating the extent of AVM nidus obliteration after embolization. MR was more sensitive than CT in revealing associated parenchymal abnormalities and subacute hemorrhage. Because of flow-related artifacts and low sensitivity in distinguishing calcification from rapid flow and/or hemosiderin, MR seemed to have a low sensitivity for detecting old hemorrhage within an AVM nidus. Angiography is still needed in the planning of either surgical or endovascular treatment of AVMs.     

脑血管畸形的MRI及MRA诊断

目的：研究脑动静脉畸形与海绵状血管瘤的ＭＲＩ及ＭＲＡ特征，评价不同的成像方法对脑血管畸形的诊断价值。材料与方法：对２１例脑动静脉畸形及６例海绵状血管瘤分别作了常规ＭＲ成像及ＭＲ血管成像，ＭＲＩ采用ＳＥＴ１和Ｔｕｒｂｏ ＳＥ Ｔ２加权序列，ＭＲＡ采用２Ｄ－ＦＬＡＳＨ及３Ｄ－ＦＩＳＰ序列，６例海绵状血管瘤ＭＲＡ仅使用２Ｄ－ＦＬＡＳＨ序列。所有成像以环形激化头线圈在１．０Ｔ ＭＲ仪上完成。结果：Ｔ１及Ｔ     

蛛网膜下腔出血患者的MRA和DSA的对照研究

目的：研究ＭＲ血管造影（ＭＲＡ）在蛛网膜下腔出血（ＳＡＨ）患者病因诊断中的应用准确性和可靠性。材料和方法：回顾性分析３３例ＳＡＨ患者的ＭＲＡ资料，并与ＤＳＡ作了对比分析，ＭＲＡ采用三维时间流逝（３Ｄ－ＴＯＦ）法。结果：ＭＲＡ上显示了２６例血管病变中的２２例，包括１５个动脉瘤中的１３个，８例动静脉畸形中的６例和３例血管狭窄闭塞性病变。１个完全血栓形成的右颈内动脉瘤ＭＲＡ上未显示。但常规ＭＲＩ和ＭＲＡ原始图像上显示，ＭＲＡ结合ＭＲＩ和ＭＲＡ原始图像可以对９１％的患者做出正确诊断和评价，动脉瘤和周围血管的关系及ＡＶＭ的供血动脉和畸形结节能在ＭＲＡ上被准确评价。结论：作为一种非损伤性的血管成像方法，ＭＲＡ具有安全、可靠和方便的优点，可以做为常规用于ＳＡＨ患者的筛选检查。     

Evaluation of 4D Vascular Flow and Tissue Perfusion in Cerebral Arteriovenous Malformations: Influence of Spetzler-Martin Grade,Clinical Presentation,and AVM Risk Factors

BACKGROUND AND PURPOSE:The role of intracranial hemodynamics in the pathophysiology and risk stratification of brain AVMs remains poorly understood. The purpose of this study was to assess the influence of Spetzler-Martin grade, clinical history, and risk factors on vascular flow and tissue perfusion in cerebral AVMs.MATERIALS AND METHODS:4D flow and perfusion MR imaging was performed in 17 patients with AVMs. Peak velocity and blood flow were quantified in AVM feeding and contralateral arteries, draining veins, and the straight sinus. Regional perfusion ratios (CBF, CBV, and MTT) were calculated between affected and nonaffected hemispheres.RESULTS:Regarding flow parameters, high-grade AVMs (Spetzler-Martin grade of >2) demonstrated significantly increased peak velocity and blood flow in the major feeding arteries (P < .001 and P = .004) and straight sinus (P = .003 and P = .012) and increased venous draining flow (P = .001). The Spetzler-Martin grade significantly correlated with cumulative feeding artery flow (r = 0.85, P < .001) and draining vein flow (r = 0.80, P < .001). Regarding perfusion parameters, perinidal CBF and CBV ratios were significantly lower (P < .001) compared with the remote ratios and correlated negatively with cumulative feeding artery flow (r = −0.60, P = .014 and r = −0.55, P = .026) and draining vein flow (r = −0.60, P = .013 and r = −0.56, P = .025). Multiple regression analysis revealed no significant association of AVM flow or perfusion parameters with clinical presentation (rupture and seizure history) and AVM risk factors.CONCLUSIONS:Macrovascular flow was significantly associated with increasing Spetzler-Martin grade and correlated with perinidal microvascular perfusion in cerebral AVMs. Future longitudinal studies are needed to evaluate the potential of comprehensive cerebral flow and perfusion MR imaging for AVM risk stratification.

Cerebral arteriovenous malformations are associated with an increased risk of intracranial hemorrhage, accounting for 2%–4% of all hemorrhagic strokes annually.¹ Previous studies have demonstrated the potential risk of hemorrhage following AVM embolization, presumably due to acute alterations in AVM or cerebral hemodynamics.² However, the Spetzler-Martin grade (SMG), widely used for surgical risk stratification in cerebral AVMs, does not provide insight into local or global hemodynamics.³ Quantitative assessment of AVM feeding and draining flow, combined with whole-brain tissue perfusion, can potentially characterize both AVM macro- and microvascular pathophysiology. In addition, the relationships between quantitative AVM hemodynamic parameters and the SMG or clinical history (rupture/seizures) and other risk factors (eg, presence of flow-induced aneurysms or venous stenosis, deep AVM location, and single or deep venous drainage) remain unclear.In this study, a comprehensive MR imaging and analysis protocol based on 4D flow and DSC perfusion MR imaging was applied for the characterization of 3D AVM macrovascular flow and microvascular brain tissue perfusion. 4D flow MR imaging can measure the 3-directional velocity field with full volumetric coverage of the vessels of interest.^4,5 Previous studies have shown that 4D flow MR imaging is highly promising in the evaluation of intracranial hemodynamics in cerebral AVMs.^6–8 To gain additional information on the impact of AVMs on cerebral tissue perfusion, we used DSC PWI based on a fast spin-echo EPI acquisition during the first pass of contrast agent through the brain vasculature to quantify microvascular perfusion biomarkers.^9,10 The AVM nidus has relatively low resistance and thus often causes high-flow transnidal shunts, which may result in hypoperfusion in the cerebral parenchyma immediately adjacent to AVMs. However, this so-called “steal effect” with diversion of blood from the adjacent tissue to the AVM nidus is still controversial, and it is unclear whether it should be considered a mechanism for the clinical presentation of cerebral AVMs.¹¹The purpose of this study was to quantitatively evaluate macrovascular flow in AVM arterial and venous networks and microvascular perfusion of the peripheral cerebral parenchyma. We investigated relationships between these quantitative hemodynamic parameters and SMG classification followed by correlation with various AVM symptomatic and anatomic risk factors.     

Cerebral arteriovenous malformations: morphologic evaluation by ultrashort 3D gadolinium-enhanced MR angiography

The purpose of this study was to evaluate the usefulness of a new ultrashort contrast-enhanced (CE) MR angiography (MRA) for the morphologic evaluation of cerebral arteriovenous malformations (AVMs). The method was compared with conventional X-ray digital subtraction angiography (DSA) and time-of-flight (TOF) MRA in 22 patients to assess the angioarchitecture of the malformations which is essential for treatment planning and follow-up. Two experienced MR readers independently evaluated both techniques with regard to the assessment of feeding arteries, AVM nidus, and venous drainage patterns. Contrast-enhanced MRA was able to detect all AVMs seen on DSA, whereas the TOF MRA failed in 1 patient with a very small AVM. In the assessment of the different vessel components of the AVM there was no difference for the detection and delineation of feeding arteries and the AVM. The venous drainage patterns could always be clearly delineated in the CE MRA, whereas TOF MRA could demonstrate the exact venous drainage in only 9 patients. Contrast-enhanced MRA was found to be superior to conventional TOF MRA in the assessment of the angioarchitecture of cerebral AVMs especially regarding the assessment of the venous drainage patterns. The superiority is supported by the improved vessel-to-background contrast and contrast-to-noise ratios. The major limitations of this new technique consist of a low spatial resolution at the used time resolution which can be improved by further sequence modifications. Contrast-enhanced MRA is thus an important additional imaging technique for treatment planning and follow-up of AVMs. Electronic Publication     

DSA对脑动静脉畸形出血的预测分析

目的:探讨脑动静脉畸形(AVM)血管造影形态与出血关系,预测脑动静脉畸形(AVM)出血的危险性。方法:回顾性分析104例数字减影脑血管畸形资料。结果:穿支动脉供血、单支引流和深部引流、小病灶及位于基底节和后颅窝者易出血。结论:通过观察脑动静脉畸形(AVM)供血动脉(类型)、大小、位置、引流静脉数目及通畅情况,可以对脑动静脉畸形(AVM)的出血情况进行预测。     

CT angiography with multidetector-row helical CT in spinal arteriovenous malformation

We performed intravenous CT angiography using multidetector-row helical computed tomography (MDCT) in a 63-year-old man with spinal arteriovenous malformation (AVM). The CT angiography demonstrated feeding arteries, varix-like structure, draining veins and their relationship to the spinal cord. Although selective angiography is essential in planning treatment for spinal AVMs as well as in establishing the diagnosis of the disease, CT angiography can be a good supplementary technique for visualizing precise location of abnormal vessels in a certain case of spinal AVM.     

Exceptional multiplicity of cerebral arteriovenous malformations associated with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome).

PURPOSETo describe the clinical and imaging features of seven patients with hereditary hemorrhagic telangiectasia and an exceptional number of cerebral arteriovenous malformations (AVMs).METHODSOne hundred thirty-six patients from a dedicated hereditary hemorrhagic telangiectasia clinic were screened systematically for cerebral AVMs by means of MR imaging. Thirty-one were found to have abnormalities suggestive of a vascular malformation. Eighteen of these 31 patients subsequently underwent diagnostic cerebral angiography.RESULTSOf the 18 patients who had cerebral angiography, all were found to have at least one AVM and seven were found to have three or more AVMs. The number of cerebral AVMs detected ranged from three to nine. At angiography, the AVMs varied in size from 3 to 25 mm in maximal dimension and consisted of a poorly defined plexiform nidus that typically had a single arterial feeding pedicle and a single draining vein. The two largest AVMs (20- and 25-mm nidus, respectively) contained intranidal aneurysms. Treatment included embolization, surgical excision, or follow-up management.CONCLUSIONSMultiple cerebral AVMs are associated with hereditary hemorrhagic telangiectasia and further highlight the uniqueness of central nervous system involvement by this systemic angiodysplasia. MR imaging can underestimate the number and size of cerebral AVMs; therefore, catheter angiography is necessary to establish the extent of central nervous system involvement in this disorder.     

Two-dimensional thick-slice MR digital subtraction angiography in the assessment of small to medium-size intracranial arteriovenous malformations

Assessment of intracranial arteriovenous malformations (AVMs) by conventional catheter angiography carries risks; moreover, this invasive procedure is often repeated for follow-up. We investigated the clinical applicability of two-dimensional thick-slice, contrast-enhanced magnetic resonance digital subtraction angiography (2D MRDSA) with high temporal resolution in the assessment of AVMs. We performed 78 2D MRDSA studies of treated or untreated small to medium-size AVMs on a 1.5 tesla imager. Two observers independently evaluated demonstration of nidus flow void on T2-weighted images and each component of the AVM on 2D MRDSA employing a three-point grading scale. In 55 patients with AVMs, the mean ratings of nidus flow voids, feeding vessels, nidi, draining vessels and early venous filling on MRI were 2.8, 2.4, 2.6, 2.8 and 2.8, respectively. sensitivity, specificity, positive and negative predictive values for an AVM using 2D MRDSA were 87, 100, 100 and 78%, respectively and for nidus flow voids on T2-weighted images 80, 91, 96 and 66%, respectively. 2D MRDSA can thus demonstrate haemodynamic features of AVMs. It can be employed as a less invasive, dynamic angiographic tool for follow-up of AVMs previously delineated by catheter angiography.     

Novel technique for evaluating complex pelvic arteriovenous malformations with catheter-directed subtracted MR angiography

Residual or recurrent arteriovenous malformation (AVM) nidal filling is not uncommon after embolization of complex peripheral AVMs. The major reason for this is incomplete embolization of the nidus owing to failure to detect all feeder vessels other than the dominant one. Herein, the authors describe a novel "intravenous minus intraarterial" subtraction magnetic resonance (MR) angiography technique that enabled the delineation of additional feeding branches not clearly identifiable at intravenous contrast-enhanced MR angiography or nonselective pelvic angiography. This technique may be particularly useful in the evaluation of complex AVMs and their subsequent management with embolization.     

MR digital subtraction angiography of cerebral arteriovenous malformations

BACKGROUND AND PURPOSE: Although phase-contrast MR angiography provides some information regarding hemodynamics of cerebral arteriovenous malformations (AVMs), most conventional MR angiographic techniques have not been helpful in this respect. We attempted to determine the value of MR digital subtraction angiography (DSA) in assessing AVM hemodynamics. METHODS: We developed an MR DSA technique by combining rapid thick-section T1-weighted imaging with a bolus injection of contrast material. The temporal resolution was 0.56 to 0.61 seconds per scan. MR DSA images obtained from 14 patients with AVMs were reviewed. Anatomic depiction of each component of the AVM was rated using a four-point grading scale (excellent = 3, good = 2, fair = 1, poor = 0) to compare conventional vs MR angiograms. RESULTS: We were able to obtain serial images in which passage of contrast material was evident within the AVM, although the sequence we used allowed images to be obtained in only one projection. The average score for feeders, nidi, and drainers was 1.6, 2.4, and 2.3, respectively, with an overall average of 2.1. CONCLUSION: The spatial resolution of our technique may fall below the level needed for identification of small vascular components of an AVM. Additionally, the limited slab may restrict application of the technique to assessment of large or very small AVMs. MR DSA, however, can show the hemodynamics of AVMs and may serve as a supplement to conventional MR imaging in the diagnosis of cerebral AVMs.     

Intracranial vascular malformations: imaging of charged-particle radiosurgery. Part I. Results of therapy

Twenty-four patients with intracranial vascular malformations were examined before and after helium ion radiosurgical treatment with angiography, computed tomography (CT), and magnetic resonance (MR) imaging. Twenty patients had high-flow arteriovenous malformations (AVMs). After treatment 18 of 20 AVMs (90%) showed a significant reduction in size on angiograms or MR images. Eleven of 20 (55%) had complete resolution on angiograms or MR images, 35% had partial resolution, and 10% showed no size change. Before treatment, the size range of the AVMs was 0.86-383 cm3 (median, 21.7 cm3). Smaller AVMs (less than 8 cm3) were more likely to resolve completely than medium-sized AVMs (8-64 cm3) or larger AVMs (greater than 64 cm3). Four additional patients had slow-flow vascular malformations: One had a venous angioma; one, a probable cavernous hemangioma; and two, malformations that were not seen on angiograms. CT proved inaccurate in demonstrating the boundaries of the AVM after treatment because it showed persistent contrast enhancement even when the AVM was completely obliterated on angiograms. MR imaging and angiography were complementary in the evaluation of therapeutic results and should be the primary modalities in the examination of patients with AVMs.     

Neuroradiologic exploration of cerebral arteriovenous malformations

MR and superselective neuroangiographic investigation of 223 patients with cerebral arteriovenous malformations (AVMs) were retrospectively analyzed with regard to topography, morphology, vascular architecture and signs of increased bleeding risk. MR proved highly efficient in defining the topography of the lesion and highly sensitive in detecting AVM-induced parenchymal changes. Superselective neuroangiography enables complete endovascular mapping of the AVM and provides relevant information on its intrinsic vascular composition. In addition, this method gives new insights into the venous drainage patterns and the unexpectedly high incidence of associated venous changes. MR-neuroangiographic correlation in each individual case forms the basis for any therapeutic decision and treatment planning. In concordance with previous statements in the literature this study disclosed that the presence of stenotic draining veins or related aneurysms on feeding arteries represents an increased risk for AVM rupture.     

De novo cerebral arteriovenous malformation: case report and literature review

We describe a rare case of a de novo cerebral arteriovenous malformation (AVM) in a 9-year-old girl. MR imaging at 6 years of age demonstrated band heterotopia. Follow-up MR imaging 3 years later demonstrated a new 3.5-cm AVM in the left parietol-occipital region, confirmed by conventional angiography. This report, along with limited previous reports, suggests that AVMs can be acquired lesions and that AVM development is a dynamic process extending into the postnatal period.     

Pressure measurements in arterial feeders of brain arteriovenous malformations before and after endovascular embolization

Arteriovenous malformations (AVMs) are composed of abnormal arterial and venous vessels in the brain causing arteriovenous shunts of arterialized blood directly from pial arteries to draining veins. The hemodynamics of these lesions is not well-understood. Changes in blood flow and pressure are probably related to the natural history of AVMs and may also play a major role in AVM treatment. In this study intra-arterial pressure was measured in feeding arteries of AVMs using a microcatheter that had been placed for subsequent embolization treatment (201 measurements were performed in 95 patients before and after the embolization procedure). Results show a direct relationship between pressure changes and degree of embolization. Since pressure changes during the embolization procedure are relatively small, it seems unlikely that these changes are the direct cause of rupture and periprocedural bleedings.     

Plasticity of the human motor cortex in patients with arteriovenous malformations: a functional MR imaging study

BACKGROUND AND PURPOSE: The capacity of the human brain to recover from damage has been explained on the basis of plasticity, according to which remaining areas assume functions that would normally have been performed by the damaged brain. Patients with cerebral arteriovenous malformations (AVMs) involving primary motor areas may present without significant neurologic deficits. We used functional MR imaging to investigate the organization of cortical motor areas in patients with AVMs. METHODS: Cortical motor hand and foot representations were mapped in nine right-handed patients harboring AVMs occupying the hand (n = 6) or foot (n = 3) region of the primary motor cortex (M1). None of the patients exhibited motor deficits. Simple movements of the hand and foot were performed. In eight patients, both right and left extremities were tested; in one patient, only the hand contralateral to the AVM was examined. Localization of activation in the affected hemisphere was compared with that in the unaffected hemisphere and evaluated with respect to the normal M1 somatotopic organization shown in earlier functional MR imaging investigations. RESULTS: Cortical activation showed three patterns: 1) functional displacement within the affected M1 independent of the structural distortion induced by the AVM (n = 4), 2) presence of activation within the unaffected M1 ipsilateral to the moving extremity without activation in the affected M1 (n = 3), and 3) prominent activation in nonprimary motor areas without activation in either the affected or unaffected M1 (n = 2). CONCLUSION: Preliminary evidence suggests that brain AVMs lead to reorganization within the somatotopic representation in M1 and to occasional abnormal expansion into nonprimary motor areas.     

Clinically documented hemorrhage in cerebral arteriovenous malformations: MR characteristics.

This study assessed the ability of magnetic resonance (MR) imaging to identify vascular characteristics of cerebral arteriovenous malformations (AVMs) which are predictive of hemorrhage. The study also evaluated the sensitivity and specificity of spin-echo (SE) and gradient-recalled-echo (GRE) imaging in the detection of prior clinical hemorrhage on the basis of location of the hemorrhage (parenchymal, intraventricular, or subarachnoid). Fifty patients with high-flow AVMs were evaluated. Twenty-four (48%) patients had prior clinical hemorrhage documented at computed tomography or MR imaging at the time of bleeding. Central venous drainage (P less than .001), central AVM location (P less than .001), and peri- or intraventricular AVM location (P less than .01) correlated positively with prior clinical hemorrhage. Intranidus aneurysms and angiomatous change could not be detected with MR. Nineteen of the 24 patients with prior hemorrhage underwent both SE and GRE imaging. Hypointensity, indicating the presence of iron from prior hemorrhage, was demonstrated in 14 of 19 T2-weighted SE images (sensitivity, 74%) and in 18 of 19 GRE images (sensitivity, 95%). No patient without a prior episode of clinical bleeding demonstrated evidence of iron deposition at MR imaging (specificity, 100%).