Chiari Malformation

About This Condition

Chiari malformation is a condition in which part of the brain extends into the spinal canal through the foramen magnum (a small hole in the base of the skull that enables the spinal cord to extend from the brain). Chiari malformations may develop as a result of a small or misshapen skull placing pressure on the brain and forcing the downward movement of the cerebellum into the spinal canal. As a result, bodily functions controlled by this area of the brain may be affected while the the flow of cerebrospinal fluid (CSF) may be blocked.

The condition affects both children and adults with symptoms ranging from headache, neck pain, hearing or balance problems, dizziness, difficulty swallowing or speaking, vomiting or gagging and fine motor coordination problems. Elevated intracranial pressure, syringomyelia (spinal cord cysts), brainstem compression, cerebellar dysfunction, cervical myelopathy, scoliosis and breathing disorders are often noted on clinical presentation.

Chiari malformations are generally caused by structural defects in the brain and spinal cord that occur during foetal development, also known as primary or congenital Chiari malformation. Acquired or secondary Chiari malformation may occur if excessive amounts of CSF is drained from spinal canal due to injury, disease or infection. Primary Chiari malformation, although rare, is the most common form of the condition.

There are several classifications of Chiari malformation:

• Type 1 - the most common form, occurs when the lower part of the cerebellum push into the foramen magnum. It is generally not diagnosed until adolescence or adulthood, typically by accident during examination for another issue. Symptoms are often not noticed until later in life.
• Type 2 - involves both the cerebellum and brain stem pushing through the foramen magnum and is often associated with myelomeningocele, a form of spina bfida where the spinal canal does not close before birth. Symptoms appear during early childhood and can be severe, potentially causing life-threatening complications.
• Type 3 - the most serious, but very rare, form of the condition where the cerebellum and brain stem herniate through an abnormal opening in the back of the skull. The condition can cause debilitating and life-threatening complications, along with severe neurological defects.