Focal abnormal conglomerations of dilated arteries and veins in the brain parenchyma
Arterial blood flows directly into draining veins without capillary beds creating high pressure channels
May rupture, causing intracerebral hemorrhage +/- intraventricular hemorrhage.  Mechanism of rupture incompletely understood.
Prevalence 0.14%
Congenital lesions
Majority are sporadic, not familial
Associated with Osler- Weber-Rendu disease and Sturge-Weber syndrome
Lifelong risk of bleeding
2-4% per year, cumulative
Arterial blood flows directly into draining veins without capillary beds creating high pressure channels
May rupture, causing intracerebral hemorrhage +/- intraventricular hemorrhage.  Mechanism of rupture incompletely understood.
Majority are sporadic, not familial
Associated with Osler- Weber-Rendu disease and Sturge-Weber syndrome
2-4% per year, cumulative
Arteriovenous malformation 
Venous angioma
Cerebral venous thrombosis
Cavernous malformation
Coma
Capillary telangiectasia
Brain abscess
Intracranial hemorrhage