Arteriovenous Malformations of the Brain
Arteriovenous malformations of the brain are focal abnormal conglomerations of
dilated arteries and veins within brain parenchyma, in which a loss of normal vas-
cular organization at the subarteriolar level and a lack of a capillary bed result in
abnormal arteriovenous shunting (Fig. 1)
Congenital and Acquired Chiari Syndrome
Chiari malformation, an anomaly of the posterior cranial
fossa, also known as Arnold–Chiari malformation, was described in autopsies
by Hans Chiari, an Austrian pathologist, in 1891. He defined four
distinct anatomical configurations in which the cerebellar tonsils (the most caudal
part of the cerebellum) protruded below the lower margin of the foramen magnum.1