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.
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.
Common Symptoms list (not limited too):
Dizziness, vertigo, disequilibrium, visual disturbances, ringing in the ears, difficulty swallowing, palpitations, sleep apnea, muscle weakness, impaired fine motor skills, pulsatile tinnitus, chronic fatigue, painful tingling of hands and feet can also be seen in scoliosis. Refer to a non-scientific poll that was conducted by Chiari Connection International. Click Here to see the results.
Considered Warning symptoms because they are related to brainstem compression, more often seen in cases where the Chiari are compounded by another condition such as basilar invagination, retroflexion of the odontoid bone, and similar disorders, severe swallowing problems, Tachyarrthymias, severe nausea (causing wasting below 90 lbs.), and central sleep apnea.
Please refer to the following resources to learn more:
Chiari Connection International
The Weill Cornell Brain and Spine Center
World Arnold Chiari Malformation Association
American Syringomyelia and Chiari Alliance Project