More than a tongue-twister, Arnold-Chiari malformation is a well-described congenital (present at birth) abnormality of the cerebellum and brain stem. While four different types have been described, types 1 and 2 are most common. Types 2, 3, and 4 are typically diagnosed in infancy because of serious abnormalities involving the skull or spinal cord. However, type 1, considered a milder form of the condition, may not cause symptoms until adulthood, if ever.
In all types, changes affect the back part of the brain and spinal cord. A portion of the cerebellum (the "balance center" of the brain) squeezes through the base of the skull next to the spinal cord. This can cause changes within the spinal cord and compression of the cerebellum and its circulation. Headache and other symptoms are common.
The headache associated with Arnold-Chiari may take on various forms, including an intermittent form or a persistent one. The pain may be frontal (as in the forehead area) or in the neck or back of the head area. Characteristically, but not always, the pain may worsen with neck movement, coughing, or straining movements. Associated neck pain is a frequent complaint. Upon examination, other problems may be found including incoordination, difficulty swallowing, impaired eye movements, sensory disturbances, and others. Arnold-Chiari is diagnosed by an MRI of the brain and spinal cord but cannot be identified by a CT scan.
If a severe malformation is present, surgery may be needed to eliminate pressure on various parts of the brain and spinal cord and relieve associated symptoms. If surgical intervention is not required, treatment is typically based upon symptom control or relieving pressure.