<unk>  can be present at birth. If the condition develops after birth, it is usually the result of injury or diseases. If due to injury, about half the time it is caused by vehicle or bicycle accidents; 25% of the time by falls and 10% of the time by recreational activities such as diving accidents. It also occurs in patients with bone diseases, such as osteomalacia, rheumatoid arthritis, Paget's disease, Ehlers-Danlos syndrome, Marfan syndrome, and osteogenesis imperfecta.
Basilar invagination
Nasal glial heterotopia
Microlissencephaly
Lissencephaly
Schizencephaly
Hemihydranencephaly
Exencephaly
Microhydranencephaly