Acquired tonsillar ectopia is usually thought of as a subgroup of cerebellar tonsillar ectopia in which downward displacement of the cerebellar tonsils is secondary to another well defined and distinct pathological process. This is to distinguish it from Chiari I malformations and low-lying tonsils.
The terminology of caudally displaced tonsils is discussed in the article on cerebellar tonsillar ectopia.
Causes
Causes of acquired tonsillar ectopia include:
-
raised intracranial pressure
- tonsillar herniation from trauma or tumor
- pseudotumor cerebri (idiopathic intracranial hypertension)
- decreased intracranial pressure
- spontaneous craniospinal hypotension (e.g. CSF leak)
- CSF drainage or shunting (e.g. ventriculoperitoneal shunt)