Spinal cavities are mostly caused by Chiari malformation (submicrocephalic tonsillar herniation). The pathogenesis of Chiari malformation may occur in the third fetal month, during the embryonic period, due to hypoplasia of the occipital portion of the mesodermal somites, resulting in a delayed lag in the development of the occipital bone, while the cerebellum and brainstem develop normally, causing the normally developing hindbrain structures to herniate into the spinal canal after birth due to excessive compression of the posterior cranial fossa. The pathogenesis of malformation combined with spinal cord cavitation: hydrodynamic theory; intracranial and intravertebral canal pressure separation theory; cerebrospinal fluid spinal cord parenchymal infiltration theory; related to abnormal cerebrospinal fluid outflow tracts in the occipital foramen area.