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Chiari I Malformation, also known as CM-I, there is a malformation of the hindbrain. The lower part of the cerebellum is referred to as tonsils. The cerebellar tonsils herniate through the base of the skull, otherwise known as the foramen magnum and into the spinal column. In addition the posterior fossa of the skull, or the back, is too small for the brain, and does not allow enough space for the brain. This in turn causes the cerebellar tonsils to be pushed down through the base of the skull, and compressed. As little as 1 millimeter of protrusion by the tonsils has been proven to cause symptoms. Chiari at level zero has also been shown to cause symptoms. When there is compression of the brain stem, involuntary bodily functions such as the beating of your heart, and breathing, cranial nerve compression and a disruption of the flow of the cerebral spinal fluid can all be affected. This type of malformation is commonly, but not always, seen in conjunction with Syringomyelia.


There is also Type I.5, Type II, Type III, Type IV and even Type 0.

What is Chiari?

Symptoms of Chiari 

Severe Headache and Neck Pain---Most Common
Visual disturbances
Ringing in the ears
Difficulty swallowing
Sleep apnea
Muscle weakness
Impaired fine motor skills
Pulsatile Tinnitus
Chronic fatigue
Painful tingling of the hands and feet
Numbness in extremities
Memory loss
Back pain
Gag reflex issues
Neck pain


The degree, location and duration of symptoms vary from patient to patient. The degree of herniation does NOT dictate if a patient is a candidate for surgery. In one case small herniation in addition to an associated disorder can cause severe symptoms and surgery may be indicated. In another case a larger herniation with relatively no symptoms may be present, and surgery may not be indicated.  Each case is evaluated on a case-by-case basis. Surgery for Chiari is a brain surgery called decompression surgery. The basis of it is that it makes more room for the spinal fluid to flow.

MRI Scans

Other Related Disorders

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