An Acquired Chiari Malformation is when the cerebellum extends out of the skull and into the spinal canal after birth; whether acquired from another inherited condition such as Ehlers-Danlos Syndromes, or one of the many developed conditions that can cause the pushing/pulling down on the brain or spinal cord: Intracranial Hypertension, Hydrocephalus, Cysts/Tumors, Tethered Cord Syndrome, Intracranial Hypotension (CSF leaks), etc. It is recommended that all Chiari Malformations are assumed to be acquired, until proven otherwise. In contrast, a “Congenital Chiari” is believed to be caused by a Posterior Fossa Hypoplasia (small posterior fossa; which is congenital), when no associated etiological cofactors can be found.