What is cerebellar tonsillar ectopia?
Cerebellar tonsillar ectopia is a common congenital dysplasia.
Cerebellar tonsillar ectopia includes four types:
- Type I is the type of lightest clinical manifestation, which is also known as primary cerebellar ectopia. Cerebellar tonsil is lowered under the level of the occipital macropores, into the spinal canal. The medulla is slightly displaced forward and downward, and the fourth ventricle is normal.
- For type II, not only cerebellar tonsil invades into the spinal canal, but also the pons, medulla, and the fourth ventricle move downward. Some structures such as the skull, dural midbrain, and cerebellum are hypoplastic.
- Type III is the most severe type. Medulla, cerebellar vermis, the fourth ventricle and part of cerebellar hemisphere invade into the upper part of the spinal canal. Obvious head and neck deformity and cerebellar malformation also exist.
- For type IV, hypoplasia of cerebellum and brainstem is obvious, but cerebellum and brainstem do not invade into the spinal canal. Patients often die in the neonatal
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Key words: cerebellar tonsillar ectopia; ectopia cerebellar tonsillar.