Acquired Chiari malformation type I associated with a supratentorial fistulous arteriovenous malformation: a case report.

A case of acquired Chiari malformation type I with frontal fistulous arteriovenous malformation (AVM) is presented, and the pathophysiology is discussed. The tonsillar herniation and hydrocephalus both resolved after AVM was excised. This case provides some insight into the complex hemodynamic change exerted by the fistulous AVM and the mechanism of the development of acquired Chiari malformation type I.