May Cause

Congenital craniovertebral junction abnormality

Fourth ventricle outlet obstruction

Hydrocephalus

May Be Caused by

 Common

Chiari II malformation

Congenital craniovertebral junction anomaly

Osteogenesis imperfecta

Osteomalacia

Paget disease of bone

Rickets

 Uncommon

Achondroplasia

Ankylosing spondylitis

Aqueduct stenosis

Atlantoaxial dislocation

Chronic hydrocephalus

Cleidocranial dysostosis

Collet-Sicard syndrome

Crouzon syndrome

Familial basilar invagination

Familial primary basilar impression

Fibrous dysplasia

Hajdu-Cheney syndrome

Hyperparathyroidism

Hypoparathyroidism

Hypophosphatasia

Klippel-Feil syndrome

Langerhans cell histiocytosis

Lowe syndrome

Metaphyseal chondrodysplasia Jansen type

Mucopolysaccharidosis

Occipital craniotomy in a child

Osteomyelitis

Osteopetrosis

Osteoporosis

Psoriatic arthritis

Pyknodysostosis

Rheumatoid arthritis

Schwartz-Jampel syndrome

Sjögren-Larsson syndrome

Syphilis

Trauma

Trisomy 21

Tuberculosis

Unfused C1 posterior arch