There are 4 types of Arnold-Chiari malformations, each with a different prognostic significance.
Findings
|
Type
|
cerebellar tonsils below the level of the foramen magnum
|
1
|
cerebellar vermis, medulla and IVth ventricle below the level of the foramen magnum
|
2
|
cervico-occipital meningomyelocoele, with parts of the cerebellum and medulla in the cavity
|
3
|
cerebellar hypoplasia AND malformation type 1, 2 or 3
|
4
|
Associations with the Different Malformation Types
Type 1:
(1) 50% with syringomyelia and/or hydromyelia
(2) 10% have hydrocephalus
Type 2:
(1) 90% with syringomyelia, dysraphism and Klippel-Feil syndrome
(2) 80% with hydrocephalus, aqueduct stenosis and cerebellar malformations
(3) 10% with other visceral malformations