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About Chiari I Malformation

Chiari I malformation is a condition in which there is crowding of the cerebellar at the base of the skull and the upper spinal area are not formed properly. For most patients, treatment for Chiari I consists of surgery to repair the abnormality and relieve symptoms. However, some patients who do not have symptoms may not need surgery. Instead they are seen routinely by their doctors for follow-up examinations.

Chiari malformation is spectrum of abnormalities in which the brainstem, cerebellum, upper cervical cord, and skull base are affected. Chiari I, the most common and least severe subtype of Chiari malformation, often goes unnoticed until symptoms arise in the adolescent or adult years of life. Most instances of Chiari I are congenital, though some can be acquired after birth.

Chiari I occurs when the improper formation of the skull base and upper spine results in the cerebellar tonsils being pushed down through the foramen magnum and into the spinal canal. Cerebrospinal fluid normally passes through the foramen magnum, so when this opening becomes partially obstructed, cerebrospinal fluid flows with more force through the narrowed opening, in turn further pushing down the cerebellar tonsils and blocking the foramen magnum.

The result is that the herniated cerebellar tonsils compress the brainstem, leading to several symptoms reflecting brainstem and cerebellum dysfunction. Also, syringomyelia may develop in the spinal cord, a condition characterized by the development of a cyst in the spinal cord.  Rarely hydrocephalus arises.

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