Chiari malformation
Pronunciation: kee-AH-ree
A structural defect in which brain tissue extends into the spinal canal, classified into types based on severity and anatomical involvement.
Full Definition
Chiari malformation is a group of disorders characterized by downward displacement of cerebellar tissue through the foramen magnum into the upper cervical spinal canal. Type I is the mildest and most common form, involving herniation of the cerebellar tonsils, while Type II (associated with myelomeningocele) involves herniation of the cerebellar vermis, medulla, and fourth ventricle. Type III and IV are rare and more severe variants. Symptoms may include headaches, neck pain, balance problems, and in severe cases, hydrocephalus or syringomyelia. The condition is named after Austrian pathologist Hans Chiari and requires careful documentation of type and associated complications in medical literature.
Usage
Usage note: May be spelled with or without hyphenation (Arnold-Chiari), though current preference is "Chiari malformation."
In Context
- "MRI revealed a Type I Chiari malformation with 12 mm of cerebellar tonsillar descent." — Radiology report
- "The patient's chronic headaches were attributed to an incidentally discovered Chiari malformation." — Neurosurgical consultation note