Chiari Malformation

Chiari malformation, also called Arnold-Chiari malformation, occurs when the part of the brain known as the cerebellum protrudes through an opening in the back of the skull and into the spinal canal. The condition is often congenital, meaning it's due to a birth defect, and is often related to other disorders such as myelomeningocele, a form of spina bifida when the bones of the spine don't form properly and membranes protrude out of the child's back.

It is estimated that this condition occurs in about one in every 1,000 births. For some children born with this condition, symptoms don't emerge until adolescence or adulthood, when injury, aging or other changes trigger symptoms such as vomiting, muscle weakness in the head and face, difficulty swallowing and varying degrees of mental impairment.

The exact cause of Chiari malformation is unknown, but may be genetic in origin. The term "Chiari Type I" refers to conditions where brain tissue extends into the spinal canal without a myelomeningocele or a visible sac-like protrusion on the mid to lower back. "Chiari Type II" describes this brain malformation with a myelomeningocele, characteristic of spina bifida. Generally, the symptoms of Chiari Type II are worse than those of Type I.

At UCSF Children's Hospital, our pediatric neurosurgeons are experts in treating Chiari malformation and other conditions, such as hydrocephalus, associated with this disorder.

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Reviewed by health care specialists at UCSF Children's Hospital.
Last updated May 8, 2007