Imaging of Chiari type I malformation and syringohydromyelia.

Chiari malformations are anatomic anomalies that comprise a broad spectrum of neurologic conditions. The most common malformation, a Chiari type I malformation, can present with a variety of signs and symptoms, most frequently an occipital Valsalva-induced headache. Cranial and spinal magnetic resonance (MR) imaging is used to identify the degree of tonsillar descent and document the presence of syringohydromyelia. The advent of cine-MR flow imaging (cine as in "cinema") has provided new insight as to the dynamic process involved in the evolution of this pathophysiology. This article reviews the neuroimaging of this fascinating disorder.