A co-existing condition with a known causal relationship. A condition is said to be “pathological” when it is believed to be in the direct “path” of what has caused another condition. Tethered Cord, Craniocervical Instability, CSF Leaks, and Intracranial Hypertension are primary examples of Pathological Co-factors to Chiari Malformations. They all can have the same root cause (Etiological Co-factor) of a Heritable Disorder of Connective Tissue (HDCT), but they are all common “direct causes” of an acquired Chiari Malformation.