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Several subtypes of atlanto-occipital dislocation are known. One suggested categorization scheme includes anterior, vertical and posterior of the head relative to the spine. Other variants with lateral or rotatory displacement have been described, as well as mixed types.
The posterior atlantooccipital membrane (posterior atlantooccipital ligament) is a broad but thin membrane [1] [2]: 99 extending between the posterior margin of the foramen magnum above, and posterior arch of atlas (first cervical vertebra) below. It forms the floor of the suboccipital triangle.
Craniocervical instability (CCI) is a medical condition characterized by excessive movement of the vertebra at the atlanto-occipital joint and the atlanto-axial joint located between the skull and the top two vertebra, known as C1 and C2.
The atlanto-occipital joint (Articulatio atlantooccipitalis) is an articulation between the atlas bone and the occipital bone. It consists of a pair of condyloid joints. It is a synovial joint .
When the occipital bone and the atlas (C1) are fused together in a condition called atlanto-occipital assimilation, it causes improper functioning of the cervical spinal nerves due to the vascular compression. Surgical procedure can decompress the nerves and reduce symptoms.
The clivus is an important landmark for checking for anatomical atlanto-occipital alignment. When viewed on a lateral C-spine radiograph, the clivus forms a line which, if extended, is known as Wackenheim's clivus line. Wackenheim's clivus line should pass through the dens of the axis or be tangential to it. [9]
Atlantoaxial instability is a common asymptomatic finding in rheumatoid arthritis patients. [3] However, it can lead to cervical myelopathy. [4] Patients with atlantoaxial instability can experience neck pain and headaches in the back of the head (occipital headaches).
The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.. The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the ...