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Atlanto-occipital dislocation, orthopedic decapitation, or internal decapitation describes ligamentous separation of the spinal column from the skull base. It is possible for a human to survive such an injury; however, 70% of cases result in immediate death .
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 may be dislocated, especially from violent accidents such as traffic collisions. [1] This may be diagnosed using CT scans or magnetic resonance imaging of the head and neck. [1] Surgery may be used to fix the joint and any associated bone fractures. [1] Neck movement may be reduced long after this injury. [1]
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 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.
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 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]
The head-tilt/chin-lift is the primary maneuver used in any patient in whom cervical spine injury is not a concern. This maneuver involves flexion of the neck and extension of the head at Atlanto-occipital joint (also called the sniffing position), which opens up the airway by lifting the tongue away from the back of the throat.