Medical conditions associated with Chiari malformations include hydrocephalus, spina bifida, syringomyelia, tethered cord syndrome and spinal curvature, according to the National Institute of Neurological Disorders and Stroke. Type 1 Chiari malformations are the most common and least severe form, and they may not cause symptoms.
Primary Chiari malformations are caused by parts of the brain stem and cerebellum being pushed into the upper spinal canal due to structural defects occurring during fetal development, according to the National Institute of Neurological Disorders and Stroke. Secondary, or acquired, Chiari malformations are caused by injury, infection or harmful substances. Often detected during adolescence, type 1 Chiari malformations are the only type that can be acquired.