Basilar invagination

The human spine is formed by individual vertebrae and connective tissue discs in between. The vertebrae form the spinal canal. There are seven cervical, twelve thoracic, and five lumbar vertebrae. The intervertebral discs are the link between the individual vertebral bodies.

The little joints that link the vertebrae together are known as facet joints. They help to stabilize the spine and, together with the intervertebral discs, allow a certain degree of mobility of the spinal cord. The spinal canal should be wide enough to allow nerve roots to float freely in cerebrospinal fluid. The front border of the spinal canal is built by the vertebral bodies and intervertebral discs, the side by the intervertebral joints (facets) and back by the ligamentum flavum (yellow band) and vertebral arches. Discs consist of an outer fibrous ring (annulus fibrosus), which surrounds an inner gel-like center (nucleus pulposus). The spinal cord and nerve roots lie within the spinal canal. The spinal cord extends downwards approx. to the 1st lumbar vertebra. Below, only nerve roots are present in the spinal canal. At the level of the intervertebral disc the nerve roots pass through the neural root foramina to exit the spinal canal. The spinal cord and nerve roots conduct electric-like signals from the skin and joints to the brain, and process of movement is initiated from the brain to the muscles.

The connection between the head and the spine is the atlanto-occipital joint. It consists of the condyles of the occipital bone and the upper joint surfaces of the 1st cervical vertebra. The 1st cervical vertebra is called the atlas. The atlas is connected to the 2nd cervical vertebra (axis) below as well.

Rheumatoid arthritis is a chronic inflammatory disease of small blood vessels and joints. Rheumatoid arthritis causes excessive growth of new cartilage. About 85% of the people with rheumatoid arthritis (RA) have pathologic changes in the cervical spine (atlanto-axial subluxation, basilar invagination). Basilar invagination (upwards migration of odontoid above foramen magnum) leads to compression of the medulla oblongata and spinal cord in the scull and spinal canal. Symptoms begin gradually and tend to worsen over months and years.

Gradually progressing inflammation and degeneration in the intervertebral joints in the cervical spine

Numbness, weakness, stiffness in the limbs and ataxic gait. Symptoms begin gradually and tend to worsen over months and years.

Pain and stiffness in the neck Pain in the hands and shoulders (pseudoradicular type)

Usually treatment is surgical

Neurological symptoms caused by compression of the brainstem

In case of brain stem compromise: 1) cervicomedullary angle <135° on MRI or 2) progressive cranial migration (> 5 mm)

To release the compressed nerve roots and/or spinal cord

To restore the protective function of the spine

Posterior occipitocervical fusion and if necessary decompression

Transoral odontoid resection