A collection of over 200 disorders involving genetic mutations of the proteins that make up the bodies connective tissues. They are all known to be carried down from one generation to the next; some are known to be autosomal dominant (only one parent has to carry the gene) and others are autosomal recessive (both parents have to carry the gene). Some HDCTs can change the growth and appearance of certain physical features, sometimes in utero (making it difficult to decipher between what is and is not normal). Most Chiari Specialists now agree that most (some even say all) cases of Chiari Malformation involve some form of a Connective Tissue Disorder.

Some HDCTs Common to Chiarians, include:

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.