6 doctors weighed in:
What is the difference between chiari malformations I and ii?
6 doctors weighed in

3 doctors agree
In brief: Extent of herniation
It is the downward displacement of the cerebellum, specifically a region called the "tonsils", through the foramen magnum. There are actually 4 types.
Type one is only tonsillar herniation, that is mild; type ii shows more herniation, to include a middle portion of the cerebellum. This type is often associated with an myelomeningocele (herniation of lining of the brain).

In brief: Extent of herniation
It is the downward displacement of the cerebellum, specifically a region called the "tonsils", through the foramen magnum. There are actually 4 types.
Type one is only tonsillar herniation, that is mild; type ii shows more herniation, to include a middle portion of the cerebellum. This type is often associated with an myelomeningocele (herniation of lining of the brain).
Dr. Lester Thompson
Dr. Lester Thompson
Thank
Dr. William Goldie
Pediatrics - Neurology
1 doctor agrees
In brief: Huge difference
Chiari i is just low lying cerebellum tonsils which is usually incidental and not relevant.
Chiari ii is a complex found in patients with spina bifida (often called arnold-chiari) including kinking of medulla, obstruction of ivth ventricle, peaking of quadrigeminal plate, fusion of thalamus, hydrocephalus, and associated with lack of closure of the spinal canal.

In brief: Huge difference
Chiari i is just low lying cerebellum tonsils which is usually incidental and not relevant.
Chiari ii is a complex found in patients with spina bifida (often called arnold-chiari) including kinking of medulla, obstruction of ivth ventricle, peaking of quadrigeminal plate, fusion of thalamus, hydrocephalus, and associated with lack of closure of the spinal canal.
Dr. William Goldie
Dr. William Goldie
Thank
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