Chiari Malformation and Syrinx

A Chiari I malformation is a brain abnormality that occurs when the cerebellar tonsils (bottom of the brain) extend through the opening at the base of the skull (the foramen magnum) and into the spinal canal. This may cause crowding in that area, which can cause neck and head pain and possibly interrupt the flow of cerebrospinal fluid (CSF). Most of the time, when tonsils are seen below the foramen magnum on an MRI, the tonsils are not crowded, do not cause any symptoms and do not require surgery.

Signs and Symptoms

When the tonsils are impacted (crowded), it can cause symptoms such as:

  • Headaches
  • Neck pain and stiffness
  • Numbness and tingling of the hands and feet
  • Clumsiness
  • Difficulty swallowing and/or increased gagging
  • Dizziness

Occasionally the crowding is severe enough to cause blockage of cerebral spinal fluid (CSF). This may lead to a cyst in the spinal cord (syringomyelia) or a back up of CSF in the brain (hydrocephalus).

Potential Causes

There is not a cause, in the vast majority of cases, for Type I. Chiari type II malformation is related to a birth defect called myelomeningocele. Type I cannot become Type II or visa versa.


Diagnosis starts with a physical exam and medical history. Other procedures and tests may be needed to diagnose, including magnetic resonance imaging ( MRI ). Chiari malformations cannot be diagnosed with a CT scan.

A full spine MRI might be used with a special technique to look at CSF flow and for buildup of CSF in the spinal cord (syrinx).

Treatment Options

There are a few treatment options for Chiari malformations:

  • Observation This may be recommended if you do not have any symptoms. Chiari I is not a progressive disease, and surgery is not recommended to prevent future problems.
  • Surgery, or a Chiari decompression, involves the neurosurgeon making a small incision on the back of the head and upper neck. The surgeon will then remove a small section of skull and part of the first bone of the neck. This is done to widen the area and create space for the brain. The dura, a layer of tissue that covers the brain, is often opened to expose the part of the brain that is protruding into the spinal canal. The dura is then put back together using a patch graft that is sewn in to help provide more room and eliminate the crowding. The incision is closed with multiple layers of sutures underneath the skin. The skin is protected with a special skin glue. This operation is carried out using general anesthesia, and is generally well-tolerated.

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