You are in: eMedicine Specialties > Radiology > BRAIN/SPINE Brain, Venous Vascular MalformationsArticle Last Updated: Aug 21, 2002AUTHOR AND EDITOR INFORMATIONSection 1 of 9
  Author: Andrew L Wagner, MD, Assistant Professor of Radiology, Instructional Faculty, University of Virginia School of Medicine; Director of Neuroradiology, Department of Radiology, Rockingham Memorial Hospital Andrew L Wagner is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, and Radiological Society of North America Editors: Robert A Koenigsberg, DO, MSc, FAOCR, Director of Neuroradiology, Professor, Department of Radiology, Drexel University College of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences Author and Editor Disclosure Synonyms and related keywords: developmental venous anomaly, DVA, venous angioma INTRODUCTIONSection 2 of 9
  BackgroundVenous vascular malformations, also known as venous angiomas or, more properly, developmental venous anomalies (DVAs), represent congenital anatomically variant pathways in the normal venous drainage of an area of the brain. Once thought to be rare, they are now considered to be the most common vascular malformation in the CNS. They may occur in as many as 2% of individuals. Commonly called venous angiomas for many years, the term developmental venous anomaly has been advocated as a more appropriate term because the entity does not consist of abnormally formed vessels; it may be merely a dilation of existing pathways. DVAs provide normal venous drainage for a section of brain and removal or thrombosis results in venous infarction and/or hemorrhage in that area. Most cases are found incidentally and although isolated reports of hemorrhage associated with a DVA exist, the incidence of associated symptoms is extremely low. Although some articles have espoused surgical treatment for this entity, this opinion is not widespread because the risk of causing an iatrogenic venous infarct appears to far exceed the risk of the lesion causing irreversible damage during the patient's lifetime. In fact, most cases of symptomatic DVAs occur when an associated cavernous angioma is present; this observation raises the possibility that the symptoms are actually caused by the cavernoma. DVAs are associated with the other CNS vascular malformations (eg, arteriovenous malformation [AVM], cavernous malformation, capillary telangiectasia) in approximately 15-30% of patients, although it most frequently occurs in conjunction with cavernous angiomas. The association is so common that the presence of a DVA on an image should prompt a search for a more clinically important cavernoma. DVAs are also associated with head and neck venous malformations and hemangiomas. PathophysiologyDVAs consist of a fine network of enlarged medullary venules that join to drain into a central venous outflow track that then drains into the superficial or deep venous system, depending on the location of the malformation (see Image 1, Image 6). They likely result from the absence of normal venous drainage, which forces the venous outflow to find an alternative course. The veins are typically separated by normal brain parenchyma and are physiologically normal, unlike the vessels in the other 3 CNS vascular malformations; however, distal stenoses can occasionally occur. When a stenosis is present, it may result in venous hypertension and conceivably may induce rupture of the tiny medullary veins that form the base of the lesion. Nussbaum et al (1998) have suggested that such venous hypertension may induce the formation of true AVMs. DVAs are characteristically found along the lateral ventricles, draining into a subependymal or cortical vein. However, they may occur throughout the brain and some have suggested that they occur within the cord as well. When they are in the posterior fossa, the drainage can occur via a variety of routes, although Damiano et al (1994) reported that most drain to the veins of the lateral recess of the fourth ventricle, the precentral veins, the longitudinal intrategmental vein, or a transpontine vein. FrequencyUnited StatesDVAs occur in approximately 2% of the population. InternationalDVAs occur in approximately 2% of the population. Mortality/MorbidityAlthough almost all DVAs are incidentally found and never cause clinical symptoms, sporadic reports of hemorrhage, seizure, and infarcts due to spontaneous thrombosis exist.
RaceNo known race predilection exists. SexGender differences in the incidence of DVAs have not been reported. AgeBecause they are thought to be congenital, DVAs can occur in persons of any age. Most often they occur in adults, likely because adults undergo MRI examinations more frequently than pediatric patients. AnatomySee Pathophysiology. Clinical DetailsClinical symptoms in DVAs are thought to be uncommon. Although headaches and dizziness have been associated with DVAs, confidently attributing such generalized symptoms to this common lesion is difficult. Most cases with symptoms that are directly related to a DVA involve a DVA thrombosis and/or adjacent hemorrhage. While some believe that DVAs can hemorrhage on their own, most notably after venous infarct in cases of spontaneous DVA thrombosis, most instances of hemorrhages with DVAs have been in patients with combined vascular malformations. Most likely, in the vast majority of these cases, the hemorrhage originated from the accompanying vascular malformation rather than from the DVA. Preferred ExaminationAlthough contrast-enhanced CT and nonenhanced MRI can reveal a DVA, the preferred imaging technique is contrast-enhanced MRI because of its excellent depiction of the small venules and draining vein. The multiplanar capabilities of MRI are especially useful because the typical configuration of a DVA is often best recognized in the coronal plane (see Images 1-2). Limitations of TechniquesAlthough standard contrast-enhanced MRI is excellent in depicting DVAs, without the use of gradient-echo or echo-planar imaging adjacent hemosiderin from associated cavernomas may not be appreciated, especially with fast spin-echo techniques. DIFFERENTIALSSection 3 of 9
Brain, Arteriovenous Malformation Brain, Capillary Telangiectasia Brain, Cavernous Angiomas Brain, MRI Appearance of Hemorrhage Brain, Stroke CT SCANSection 4 of 9
FindingsDVAs are typically not visible on nonenhanced CT scans but they can be visualized after the administration of contrast material. They appear as a large vascular structure in the brain parenchyma that drains into the deep or superficial venous system. The smaller surrounding veins are usually arranged in a radial pattern around the central vein. DVAs do not have a surrounding mass effect or edema and the adjacent brain is typically normal. Degree of ConfidenceThe typical appearance of a DVA on CT scans is often diagnostic but MRI may be needed in atypical cases, particularly those involving the posterior fossa where CT is limited because of streak artifacts. False Positives/NegativesAlthough AVMs can occasionally be mistaken for DVAs on CT scan and vice versa, differentiation between the two is usually not a problem because AVMs have large feeding arteries, tortuous vessels, and abnormal adjacent brain parenchyma that are not observed in DVAs. MRISection 5 of 9
FindingsOn contrast-enhanced MRI, the cluster of veins in DVAs has a spoke-wheel appearance (see Image 6); the veins are small at the periphery and gradually enlarge as they approach a central draining vein (see Image 1, Image 2). This appearance has also been referred to as caput medusa, or the head of Medusa, because of the serpentine appearance of the curvilinear peripheral draining veins. The intervening brain parenchyma is normal; this is a distinguishing characteristic of a DVA. The draining vein has a fairly straight course toward the deep or superficial venous drainage system, depending on the location of the DVA. When it is adjacent to the lateral ventricles, the draining vein usually merges with a subependymal vein, which may be enlarged. Other DVAs may drain into cortical veins or dural sinuses in the supratentorial brain (see Images 10-11). Infratentorial DVAs have a variety of possible drainage pathways without a clearly dominant one. On T2- and proton density–weighted images, the draining vein may demonstrate increased signal intensity, particularly on standard spin-echo images. This appearance is caused by gradient moment nulling. If the vessel is obliquely oriented, a yin-yang appearance may occur because the high signal intensity is misregistered and a signal void appears next to a similarly shaped area of increased signal intensity (see Image 3). In the absence of an accompanying vascular malformation, the surrounding brain tissue should have normal characteristics on T2-weighted images (see Image 7), although a case in which gliosis surrounded a DVA has been reported. Nonenhanced T1 ages may show the draining vein as a flow void but DVAs are often difficult to visualize without the use of contrast material. Fluid-attenuated inversion recovery (FLAIR) images may be relatively normal or can show a subtle increased signal (see Gradient-echo images often show decreased signal intensity in the venous angioma that is not due to hemosiderin but is secondary to the paramagnetic effects of deoxyhemoglobin in the venous blood (see Image 9). Findings on diffusion images are usually normal. Magnetic resonance (MR) venography is not necessary in almost all cases. If obtained, venograms show the draining vein with some of the surrounding radially arranged veins. Because the DVA provides the venous drainage for a section of brain, anatomically normal venous drainage is not present in that area. Because DVAs are often associated with other CNS vascular lesions (particularly cavernous angiomas), when a DVA is identified, carefully evaluate the brain and obtain gradient-echo (GRE) images (see Image 4). Cavernomas typically appear as focal areas of blood products that often show different stages of evolution (ie, hemosiderin with extracellular methemoglobin). Capillary telangiectasias are small areas of lacelike enhancement that are dark on GRE images without signal intensity abnormality on T2-weighted images. AVMs have enlarged feeding arteries and tortuous vessels with surrounding gliosis. Degree of ConfidenceMRI findings are diagnostic in almost all instances. However, in cases with questionable findings, MR venography usually suggests the diagnosis. ANGIOGRAPHYSection 6 of 9
FindingsDVAs found on angiograms are almost invariably incidental findings, as they are with newer MRIs, and the diagnosis can be made in almost every instance. When observed, the DVA appears as a blush of contrast enhancement during the venous phase of the study and drains into a large anatomically anomalous vein. In its most frequent location (adjacent to the lateral ventricles), the vein usually drains into a subependymal vein, although superficial drainage also occurs. Degree of ConfidenceA DVA has a characteristic angiographic appearance and should not be confused with an AVM; no early filling occurs with a DVA. INTERVENTIONSection 7 of 9
Medical/Legal Pitfalls
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REFERENCESSection 9 of 9
Brain, Venous Vascular Malformations excerpt Article Last Updated: Aug 21, 2002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
