Acquired Chiari Type i Malformation Associated with Type IV Dural Arteriovenous Fistula: Case Report

Background  Chiari malformations, usually congenital, can rarely be associated with arteriovenous (AV) fistulas. We present the first case involving a type IV dural AV fistula with a Chiari type I malformation. Methods  Retrospective chart review was performed to obtain pertinent details regarding history and examination, pathologic findings, and treatment course. Results  A 63-year-old woman with a 2-year history of migraines presented with 5 months of occipital, right-sided headaches and neck pain exacerbated by Valsalva maneuvers. Computed tomography (CT) and magnetic resonance imaging (MRI) of the head showed a possible right occipital AV malformation, bilateral cerebellar subdural hygromas, and tonsillar crowding at the foramen magnum indicating an acquired Chiari type I malformation. Angiography demonstrated a Cognardtype IV right posterior occipital dural AV fistula supplied by bilateral middle meningeal and posterior meningeal arteries. Conclusion  After treatment of the dural AV fistula, hygroma evacuation, and decompression of the acquired Chiari malformation, the patient's Valsalva-induced headaches abated.