Term
| Congenital anomaly whereby all or part of atlas is connected to the occiput. Is caused by a failure of segmentation and separation of the most caudal occipital sclerotome during the first few weeks of fetal life. |
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Definition
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Term
| Non-recognition of this condition is common due to the wide variation in fusion types, subtle findings and obscuration when vies are not taken in true anatomic position. Therapy options need to be evaluated as to the effectiveness and risk. Extension and rotational maneuvers may place the spinal cord and vertebral arteries at risk. |
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Definition
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Term
| Lack of ossification of the posterior arch of atlas. It may be complete and bilateral or unilateral agenesis; or it may manifest as small clefts (spina bifida). |
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Definition
| Agenesis of the posterior arch of C1 |
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Term
| The integrity of the transverse ligament is rarely compromised. Cervical flexion-extension radiographs should be taken to evaluate the atlantodental interspace. Associated hypertrophy of the posterior atlantoaxial ligaments may be a factor for cord injury after trauma. |
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Definition
| Agenesis of the posterior arch of C1 |
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Term
| The total absence of the dens |
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Definition
| Agenesis of the odontoid process |
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Term
| With atlantoaxial instability, neurological symptoms from dysfunction fo the cerebellum, brainstem, and cervical cord may occur. Prolonged hyperextension in the prone position may initiate neurological complications. |
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Definition
| Agenesis of the odontoid process |
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Term
| Ossification or calcification of the oblique portion of the atlanto-occipital membrane that bridges the posterior lateral mass and the posterior arch. |
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Definition
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Term
| The clinical significance relates to possible vertebrobasilar insufficiency during rotary manipulations of the cervical spine. It may compress or restrict the vertebral artery, which may temporarily diminish blood flow to the base of the brain. |
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Definition
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Term
| Embryological failure of normal spinal segmentation resulting in fusion of one or more contiguous vertebral segments. |
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Definition
| Congenital synostosis AKA: blocked vertebrae |
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Term
| Clinical syndromes may occur due to posterior joint changes, degenerative disc disease, spinal stenosis, fractures, and alteration and anomaly of the vertbrobasilar blood flow. Most clinical manifestations occur at the immediately adjacent segments which are under greater biomechanical stress. Blocked vertebra of C2-C3 can cause laxity of the transverse ligamnet resulting in instabiity. MVA, industrial or sports injury, or physical assault may lead to cord compression of C2/C3 blocked vertebra due to rupture of transverse ligament. |
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Definition
| Congenital synostosis AKA: blocked vertebrae |
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Term
| Congenital fusions involving more than one motion segment (more than two vertebrae). |
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Definition
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Term
| patients at highest risk for neurological complications are those with atlantoaxial anomolies, more than one blocked vertebrae, and degenerative changes at the adjacente mobile levels. The presence of intersegmental instability on flexion-extension radiographs may be associated with neurological symptoms. The vertebral artery is prone to anomalous development, and vertebrobasilar ischemia and infarctiion have been recorded. |
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Definition
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Term
| Congenital bone bars that extend between the occiput and transverse processes of the atlas. They may be unilateral or bilateral. It is attached to the atlas transverse process and directed superiorly toward the adjacent occiput. |
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Definition
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Term
| A single case has been linked with post-traumatic basal subarachnoid hemorrhage. Given the association with occipitalization there is an increased potential for brainstem anomaly. |
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Definition
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Term
| Focal ossification in the nuchal ligament representing degenerative changes. Usually seen in lower cervical spine. Edges are smooth and well-marginated. |
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Definition
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Term
| There is no relationship to previous trauma or to pain syndromes. No clinical implications. |
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Definition
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Term
| Anterior or posterior non-union of the atlas. |
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Definition
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Term
| Important to differentiate from fracture on imaging. An association with brain tumors of the posterior fossa of the skull and atlas has been recorded. Axial compression trauma may result in fracture through the site of non-union. |
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Definition
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Term
| Anterior Spondyloschisis defect |
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Definition
| spina bifida (bipartite atlas). |
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Term
| Posterior Spondyloschisis defect |
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Definition
| Spina bifida oculta (SBO). |
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Term
| A condition describing a cephalad position of the upper cervical vertebra to the base of the skull. There are two types: Primary and Secondary. Primary is congenital and associated with other vertebral defects such as occipitalization, spina bifida occulta, odontoid anomalies, and agenisis or hypoplasia of atlas. Secondary is an acquired condition resulting in softening of the occipital bone. |
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Definition
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Term
| can be complicated by sudden hearing loss, pyramidal tract signs, posterior column signs, and wasting of the upper limbs. Abnormalities in somatosensory-evoked potentials and abnormal brainstem auditory-evoked potentials may also be noted. A high incidence of vertebral artery abnormalities may be a risk factor for vertebrobasilar vascular complications. A lethal spinal cord injury following hyperextension of the cervical spine was reported in a patient. |
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Definition
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Term
| Non-union of the dens with the axis body. |
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Definition
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Term
| Instability of C1 on C2 carries the risk of damage to the spinal cord or vertebral arteries with or without trauma. High-velocity, spinal manipulative techniques are contraindicated in patients. Anesthetic risk during intubation with neck extension needs to be considered. Surgical consultation must be considered for patients with progressive instability or neurological symptoms. |
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Definition
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Term
| A costal bony process that originates from the C7 vertebra and forms true articulations with the transverse process and vertebral body. |
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Definition
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Term
| Although the majority remain asymptomatic, awareness of serious complications, including thrombosis and aneurysm, needs to be considered. Are one of many causes for neurovascular compression syndromes of the upper limb, cervical disc disease, clavicle fractures, anterior scalene muscle lesions, poor shoulder girdle muscle tone, and apical lung pathologies. |
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Definition
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