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doi: 10.1097/01.NNN.0000394652.14613.7b
DEPARTMENTS: Your Questions Answered

Langston Holly, M.D., is associate professor and co-vice chief of clinical affairs for the department of neurosurgery at the University of California Health System, and a member of the Comprehensive Spine Center in Santa Monica, CA.

Q A recent MRI showed I have Chiari Malformation Type I, but I don't have any symptoms. Should I see a doctor?




A Chiari Malformation Type 1 (CIM) occurs when the cerebellum—the lowest part of the brain, which controls balance and coordination—descends through the opening in the bottom of the skull. As a result, the cerebellum is forced into the area between the brain and spinal canal (called the foramen magnum), which is filled with cerebrospinal fluid. This may cause a blockage in the normal flow of the cerebrospinal fluid between the brain and the spinal canal resulting in headaches, neck pain, and vision and hearing problems.

It had been estimated that CIMs occur in one in every 1,000 births. However, the increased use of diagnostic imaging suggests CIMs may be more common, according to the National Institute of Neurological Disorders and Stroke Web site (

If a patient has a relatively mild CIM without symptoms that is discovered incidentally, I would recommend observation of the CIM but not surgery. If the patient has a large CIM as well as a syrinx—when the cerebrospinal fluid enters the spinal cord because of an obstruction in its normal flow—I recommend surgery. A CIM and syrinx left untreated can injure the spinal cord tissue and cause neurologic problems, such as weakness in the arms or legs, bowel or bladder problems, and pain. Even in the absence of these symptoms, I recommend surgery if the patient has both a large CIM and syrinx to prevent any long-term neurologic complications.

©2011 American Academy of Neurology