Vascular Brain Lesions (Congenital)
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- Developmental venous anomalies (DVAs) are the most common vascular malformation of the brain, representing 60% of all central nervous system vascular malformations. Also known as venous angiomas, DVAs are made up of a cluster of venous radicles that drain into a collecting vein. They occur in 2.5–3% of the general population.
- DVAs are associated with cavernous malformations (see below) in 8–40% of cases, and 20% of patients with mucocutaneous venous malformations of the head and neck have DVAs. They are also associated with sinus pericranii, a communication between intracranial and extracranial venous drainage pathways in which blood may circulate bidirectionally.
- Cavernous malformations (CMs), also known as cavernous hemangiomas or cavernomas, are multilobulated, low-pressure, and slow-flow vascular structures filled with blood, thrombus, or both. They do not contain elastin or smooth muscle. There is no intervening brain tissue except at the periphery of the lesion.
- Arteriovenous malformations (AVMs) are abnormal clusters of vessels that connect arteries and veins without a true capillary bed and have intervening gliotic brain tissue.
- Vein of Galen malformations (VOGMs) are a specific type of congenital AVM that involves the vein of Galen, which flows into the straight sinus after draining the internal cerebral veins and basal veins.
- Sturge-Weber syndrome (SWS), also known as encephalotrigeminal angiomatosis, is characterized by leptomeningeal angiomatosis, facial port-wine stain (capillary malformation), and glaucoma. Some patients have all 3 findings, although others have just 1 or 2 features.
- DVAs are an extreme variation of normal venous development. Typically, venous drainage in the brain occurs through a superficial system and a deep system. DVAs result when a deep venous territory drains toward the surface or when a superficial territory drains to the deep venous system instead of draining in the expected direction. Intervening brain tissue is normal. The mechanism responsible for DVA formation is unknown.
- The pathogenesis of CMs is unknown, although the report of cases of new cavernoma development adjacent to a DVA suggests that DVAs may lead to CM formation. Most CMs occur sporadically, although familial syndromes exist. Several genes have been associated with familial CMs.
- The cause of AVM formation is unknown. A failure of normal capillary development with dysplastic vessels forming between primordial arteriovenous connections has been suggested.
- VOGMs are embryonic AVMs consisting of choroidal arteries draining into the precursor of the vein of Galen. They develop between weeks 6 and 11 of fetal life.
- SWS occurs sporadically in 1/40,000–50,000 births and is associated with a somatic mosaic mutation in guanine nucleotide–binding protein G(q) subunit alpha. The pathophysiology is thought to be venous dysplasia, in which the primordial venous plexus that is normally present at 5–8 weeks of gestation fails to regress. The location of this plexus around the cephalic end of the neural tube and under the ectoderm destined to form the facial skin accounts for the clinical features. Venous stasis occurs due to the absence of normal cortical venous structures, and hypoperfusion of brain tissue occurs. These findings are unilateral in the majority but can be bilateral in up to 20% of cases.