Chiari malformation is a structural defect in the cerebellum, the part of the brain that controls balance.
What Is Chiari Malformation?
Normally the cerebellum and parts of the brainstem sit in an indented space at the lower rear of the skull, above the foramen magnum (a funnel-like opening to the spinal canal). When part of the cerebellum is located below the foramen magnum, it is called a chiari malformation (CM).
CMs may develop when the bony space is smaller than normal, causing the cerebellum and brainstem to be pushed downward into the foramen magnum and into the upper spinal canal. The resulting pressure on the cerebellum and brainstem may affect functions controlled by these areas and block the flow of cerebrospinal fluid (CSF) — the clear liquid that surrounds and cushions the brain and spinal cord — to and from the brain.
CMs may be congenital, or present at birth, the result of structural defects in the brain and spinal cord that occur during fetal development. They also may develop later in life if spinal fluid is drained excessively from the lumbar or thoracic areas of the spine either due to injury, exposure to harmful substances or infection.