[Click Here to Watch a video on Zion's Journey with Chiari Malformation]


Dr. Holly Gilmer is the leading expert in Chiari malformation decompression. Click here to see her explanation of this disease and treatment options, as well as watch other videos of Chiari patients and their experience with Dr. Gilmer.

Chiari malformation (kee-AHR-ee) is a disease of the brain where brain tissue is pushed down into the spinal canal. It occurs when the base of the skull (foramen magnum) is abnormally small and misshapen, causing pressing on the brain which forces it downward.

Chiari malformation (CM) may cause blockage in the flow of the cerebrospinal fluid, which may cause the normal fluid spaces in the brain to enlarge, also known as hydrocephalus.

The most common type is Chiari I. It is often associated with scoliosis and syringomyelia and does not cause problems during childhood. In teen and adult years, problems which may develop may include frequently persistent headaches, neck pain, and weakness and/or numbness in the arms and legs.

Chiari II is also known as Arnold-Chiari Syndrome. It is associated with Myelomeningocele – a kind of spina bifida – which is a birth defect in which the spinal column does not close before birth. Chari II is associated with hydrocephalus, too much fluid on the brain, causing the brain stem to shift. This is most commonly diagnosed when the patient is a young child.

Chiari III is usually associated with occipital or cervical encephalocele and hydrophalus. This type usually accompanies severe neurological defects, which are frequently incompatible with life.

Chiari IV is the least common form, and results in lack of development of the cerebellum.


In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that CM may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if ever.

CMs occur more often in women than in men and Type II malformations are more prevalent in certain groups, including people of Celtic descent – Irish, Scottish or Wales (Great Britain).

National Institute of Neurological Disorders and Stroke indicate that 1 in 1,000 babies are born with the malformation. Some are into adulthood when they are diagnosed – either intentionally or incidentally with an MRI.


Adults with CM may complain of:

  • neck pain
  • balance problems
  • muscle weakness
  • numbness or other abnormal feelings in the arms or legs
  • dizziness
  • vision problems
  • difficulty swallowing
  • ringing or buzzing in the ears
  • hearing loss
  • vomiting
  • insomnia
  • depression
  • headache made worse by coughing or straining
  • hand coordination and fine motor skills may be affected

Symptoms may change for some individuals, depending on the buildup of CSF and resulting pressure on the tissues and nerves. The severity of symptoms and whether CSF fluid is blocked determines if surgery is recommended.

Symptoms in infants with any type of CM may include:

  • difficulty swallowing
  • irritability when being fed
  • excessive drooling
  • a weak cry
  • gagging, vomiting or reflux
  • arm weakness
  • a stiff neck
  • breathing problems
  • developmental delays
  • inability to gain weight

As an infant, the child may have failure to thrive, gastroesophageal reflux, may not be sitting by six to seven months, or not walking by about 14-15 months. Older children may have headaches, dizziness, ringing in ears, problems with vision. One of the most frequent presentations is scoliosis with infrequent headaches, and no other symptoms.


Generally, an MRI is the preferred diagnostic test to determine if a cerebellar herniation exists. CT and traditional X-ray is also used, but are not as effective at diagnosing CM.


Surgical treatment to correct the compression involves removing a portion of the skull and usually part of the C1 vertebra. At this point the covering of the brain (dura) will likely be opened and a patch of similar material sewn in to make this covering (or dura) larger. The cerebellar tonsils may also be removed. This is done to return the flow of spinal fluid which relieves some or all of the symptoms as pressure is removed from the brain stem. This usually leads to shrinkage of any syrinx (spinal fluid) that might exist. The surgical procedure frequently keeps symptoms from getting worse or coming back.

For adults, some choose to manage their symptoms without surgery until if and when their symptoms become intolerable. Nearly 100% of the time patients who noted headaches as their symptoms improved. It is important to recognize that the size of the herniation of the brain (in millimeters) into the spine is not as important as the symptoms the patient experiences when deciding if surgery is an option.


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