brain, spinal cord, and nerve disorders
Craniocervical Junction Disorders
Causes of Craniocervical Junction Disorders
Craniocervical junction disorders may be present at birth (congenital) or acquired later. Some craniocervical junction disorders—called isolated disorders—affect only the craniocervical junction. Other craniocervical junction disorders result from conditions that also affect many other parts of the body (general or systemic disorders). Isolated disordersinclude the following: Atlantoaxial subluxation or dislocation: The first and second spinal bones are misaligned, sometimes putting pressure on the spinal cord. Atlas assimilation: The occipital bone and first spinal bone are fused. Atlas hypoplasia: The first spinal bone develops incompletely. Basilar invagination: Part of the second spinal bone is pushed up and partly into the skull. As a result, the neck is shortened, and pressure is put on parts of the brain, nerves, and spinal cord. Klippel-Feil malformation: The first two spinal bones are fused, or the first spinal bone is fused to the skull. As a result, movement of the neck is limited. Usually, this disorder causes no other problems, except sometimes spinal cord damage after a minor injury. Os odontoideum: Part of the second spinal bone is detached from the rest of the second spinal bone. Platybasia: The bone at the base of the skull (occipital bone) is flattened. It is often accompanied by Chiari malformation (protrusion of the cerebellum, which controls balance, through the opening in the occipital bone). The protruding cerebellum may put pressure on the brain stem or spinal cord. People with this disorder have a short neck. General disordersmay cause the same abnormalities as isolated disorders, but the abnormalities occur as part of a disorder that affects the body as a whole, as in the following: Disorders that affect bone formation in children (such as achondroplasia): These disorders affect all newly developing bone, particularly the long bones in the arms and legs. The long bones may be abnormally short and malformed, causing Osteochondrodysplasias . These disorders sometimes also cause the opening in the occipital bone to narrow or the occipital bone to fuse with the first spinal bone (atlas assimilation), putting pressure on the brain stem or spinal cord. Down Syndrome (Trisomy 21) , Craniocervical junction disorders may occur later in life. They can result from injuries or certain disorders. Injuries may affect bone, ligaments, or both. They are usually caused by motor vehicle or bicycle accidents, falls, or often diving. Some injuries are immediately fatal. The most common disorders that affect craniocervical structures are Rheumatoid Arthritis (RA) None Paget Disease of Bone None Tumors can also affect craniocervical structures. If tumors spread to the bones of the neck ( Metastatic Bone Tumors ), the first two spinal bones may become misaligned. A rare, slow-growing bone tumor called a 