Chiari Malformations


  • Chiari malformation is an abnormality of the anatomy at the bottom of the skull and brain leading to neurological symptoms.
  • There are 4 types of chiari malformations:  Chiari type 1, 2, 3 and 4.
  • Chiari type 2 is a developmental malformation that leads to myelomeningocele (incomplete closure of the back and spinal cord), hydrocephalus (too much cerebral spinal fluid in the brain), and brain abnormalities. These are often operated on at birth or soon after. 
  • Chiari type 3 and 4 are not compatible with life.
  • This page will cover Chiari Malformation type 1.


Signs and symptoms are related to two anatomic issues. Number one, because the tonsils are too low, there is crowding of the lower part of the brain.  This can lead to headaches especially with coughing, leaning over, or while having a bowel movement. Sometimes people can have neck pain. If there is more compression on the brain, it can lead to numbness, weakness, incoordination, and even trouble breathing or swallowing. Number two, sometimes patients with chiari 1 malformation develop a syrinx. This is when there is fluid in the middle of the spinal cord. If this were to happen, patients would more likely to experience weakness, numbness, bowel/bladder changes and incoordination.


The diagnosis of chiari 1 malformation is made based on imaging, clinical exam, and by symptoms. Many patients have imaging findings that have chiari 1 but do not have the symptoms of it. These patients should not be treated. Imaging ideally includes MRI (magnetic resonance imaging) of the brain and spine. A CT (cat scan) can also diagnose a chiari 1.


For patients who have imaging findings of chiari along with symptoms, the only treatment for chiari 1 malformation is a chiari decompression. This surgery removes part of the bone in the back of the skull to give the brain more room. We often remove the back part of the first cervical bone. After removal of the bone, many surgeons will then open up the dura (a thick membrane that hold the brain and spinal cord in place) and sew in a large patch to give the brain even more room. Some surgeons will even shrink the tonsils down. There is debate among surgeons which method is the best method.