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The distance between the atlas and the occipital condyles, the atlanto-occipital interval (AOI), should measure less than 4 mm, and is better assessed on coronal images. [ 4 ] The Powers ratio was formerly used, which was the tip of the basion to the spinolaminar line, divided by the distance from the tip of the opisthion to the midpoint of the ...
In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine and is located in the neck. The bone is named for Atlas of Greek mythology , just as Atlas bore the weight of the heavens, the first cervical vertebra supports the head . [ 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. [21] [22] [23]
In human anatomy, arcuate foramen, also known as ponticulus posticus (Latin for "little posterior bridge") or Kimmerle's anomaly, [1] refers to a bony bridge on the atlas (C1 vertebra) that covers the groove for the vertebral artery. It is a common anatomical variation and estimated to occur in approximately 3-15% of the population.
Symptoms are frequently worsened by a Valsalva maneuver, or by being upright for long periods of time. The reason that being upright is problematic is that gravity allows increased interaction between the brain stem and the top of the spinal column, increasing symptoms. Lying in the supine position can bring short-term relief. Lying supine ...
The atlas (C1) and axis (C2) are the two topmost vertebrae. The atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the skull and spine. It lacks a vertebral body, spinous process, and discs either superior or inferior to it. It is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.
Surgery may be used to fix the joint and any associated bone fractures. [1] Neck movement may be reduced long after this injury. [1] Such injuries may also lead to hypermobility, which may be diagnosed with radiographs. [2] This is especially true if traction is used during treatment. [2]
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 ...