Developmental Venous Anomalies

Introduction

Developmental venous anomalies (DVAs) are rare, usually asymptomatic congenital cerebrovascular malformations consisting of a radial network of medullary veins draining into a dilated central channel. Originally called venous angiomas, DVAs are functional variants of normal venous anatomy that drain brain parenchyma, which is better described by the DVA nomenclature . DVAs have a 2.5% incidence in postmortem studies and are the most common developmental vascular malformation . There are no known genetic risk factors, but DVAs are associated with cavernous malformations . Up to 33% of patients with DVAs are comorbid for cavernous malformations . If a DVA possesses features of other vascular anomalies, it is considered a “mixed” vascular malformation .

DVAs are thought to be congenital remnants of fetal venous vasculature. They likely arise due to an arrest of venous development and persistence of fetal medullary veins and the large collecting trunk into which they drain during 6–12 weeks of gestation . Venous drainage of the brain parenchyma can be conceptualized as two primary cortical periependymal routes consisting of superficial pial veins and deep medullary veins . DVAs serve as the sole venous drainage for regions of brain tissue that lack pial or medullary venous drainage, draining into normal collecting veins outside of the parenchyma . It has been proposed that recurrent subclinical microhemorrhages from a DVA can promote angiogenesis and predispose the patient to cavernous malformations .

Radiopathological Characteristics

The characteristic caput medusae (so called because of its resemblance to the head of the Greek god, Medusa) appearance of a DVA can be seen using contrast angiography ( Fig. 96.1A–B ) . DVAs consist of thin-walled, dilated medullary veins draining into a large central trunk lacking a smooth muscle or elastic layer and without direct arterial supply . The collecting vein can be identified by contrast-enhanced computed tomography (CT) ( Fig. 96 1C–D ), but is best visualized using gadolinium-enhanced magnetic resonance imaging (MRI) ( Fig. 96.1E–H ), which would demonstrate trans-cerebral linear flow voids with radial extensions on T2 sequences . Magnetic resonance (MR) angiography is particularly useful for identifying associated malformations, such as cavernous malformations, which typically appear in close proximity to the DVA . Diagnostic cerebral angiography is typically not applied for further characterization of lesions identified on CT or MR, especially since the associated cavernoma is angiographically occult.