Anastomoses between pial veins and subependymal veins which are recognized as transcerebral veins also exist ( Fig. In the fourth zone, which is named the subependymal zone, the veins coming from the third zone converge to form subependymal veins. These venous stems run deep and converge in the palmate zone (the third zone). Deep medullary veins are transversely connected to the main venous stem in the candelabra zone. The second zone is named the candelabra zone and is the most conspicuous of the four. The first zone, the so-called bamboo branch union, is the most superficial zone and is located in the white matter. Deep draining veins run deep and form the four zones of venous convergence on their way to reaching the subependymal veins. Superficial draining veins include pial veins, intracortical veins, subcortical veins, and superficial medullary veins. Parenchymal veins are divided into superficial and deep draining veins. To understand DVAs, it is important to know the structure of medullary veins. 6– 12) Here, we reviewed the current concepts of DVAs and suggest that although DVAs serve as normal venous drainage, they are associated with potential weaknesses on the basis of the angioarchitectural characteristics. Although symptomatic DVAs are rare, several abnormalities on images of DVAs have been demonstrated. 5) DVAs are usually benign and incidentally discovered. Although the etiology is still under debate, they are generally accepted to result from the focal arrest of medullary vein development or occlusion of the medullary veins between Padget’s fourth and seventh stages. 4) DVAs are composed of dilated centripetally draining medullary veins and merge into a collecting transcerebral vein that opens into either superficial subcortical veins or subependymal veins, thus forming the so-called caput medusae. suggested that they should be considered as normal anatomic variants and should be differentiated from venous angiomas and vascular malformations. 3) Since then, various terminologies have been used, such as venous malformation, venous angioma, and medullary venous malformation, implying that they were considered to be rare lesions, conferring a high hemorrhage risk. reported regarding the first patient who died of intracranial hemorrhage because of a lesion that was diagnosed as a venous angioma. 1) Since the advent of magnetic resonance imaging (MRI), the detection rate was 0.48–0.7%.
#Developmental venous anomaly series
Although DVAs should be considered benign and clinically silent, they can have potential venous hypertension and can be vulnerable to hemodynamic changes.ĭevelopmental venous anomalies (DVAs) are the most frequently encountered common form of vascular malformations with a reported incidence of up to 2.6% in a series of 4069 brain autopsies. With the advance of diagnostic imagings, perfusion study supports this hypothesis demonstrating that some DVAs have venous congestion pattern. These phenomena are considered to be the result of venous hypertension associated with DVAs.
Brain parenchymal abnormalities surrounding DVA and cerebral varix have also been reported. There are some possibilities that DVA affects the formation and clinical course of CM because CM related to DVA is generally located within the drainage territory of DVA and is more aggressive than isolated CM in the literature. However, in cases of DVAs associated with hemorrhage, cavernous malformations (CMs) are most often the cause rather than DVAs themselves.
The pathomechanisms of symptomatic DVAs are divided into mechanical, flow-related causes, and idiopathic. DVAs per se are benign and asymptomatic except for under certain unusual conditions. Their etiology and mechanism are generally accepted that DVAs result from the focal arrest of the normal parenchymal vein development or occlusion of the medullary veins as a compensatory venous system. DVAs are composed of dilated medullary veins converging centripetally into a large collecting venous system that drains into the superficial or deep venous system. However, DVA is considered to be rather an extreme developmental anatomical variation of medullary veins than true malformation. Developmental venous anomalies (DVAs), previously called venous angiomas, are the most frequently encountered cerebral vascular malformations.
0 kommentar(er)
