Rheumatoid arthritis (RA) is a condition that causes progressive inflammation and destruction of the joints in the human body. The longer a person has RA, the greater the odds that RA will attack the joints in the spine. Those who have had RA for more than 10 years have at least a 60 percent chance of cervical (upper) spine involvement. Effects on the spine can lead to problems of movement in the head, neck and limbs.
Compression of Nerves and Spinal Cord
RA inflames and destroys joints throughout the body, including joints in the spine. As these joints are destroyed, vertebrae can shift and compress the spinal cord and surrounding nerves and arteries. Shifting of vertebrae is called spondolisthesis, and it can occur in either the lower (lumbar) or upper (cervical) region of the spine. Compression of the spinal nerves can cause weakness or tingling in the limbs and motor and balance problems. Compression in the lumbar vertebrae can cause bowel or urinary incontinence or urinary retention, as well.
When spondolisthesis and nerve compression occur in the cervical spine near the base of the skull, the pressure on the vertebral arteries can lead to reduced blood flow. If the head or neck is kept in a certain position, all blood flow can be cut off, leading to black-out spells.
Atlantoaxial Instability
RA can attack the joints in the upper cervical spine, causing severe joint instability. The most common type of cervical spine instability caused by RA is called atlantoaxial instability. Atlantoaxial instability can result from the destruction of the ligaments between the first (C1) and second (C2) cervical vertebrae, which are responsible for assisting in turning the head from side to side. Excessive motion between the C1 and C2 vertebrae can cause abnormalities in head and neck motion and lead to compression of the spinal cord and nerve pain. Some patients may experience a clunking sensation when extending the neck.
Superior Odontoid Migration
The second most common cervical spine effect caused by RA is called superior odontoid migration. The second cervical vertebra has a specialized projection called the odontoid (or dens, odontoid projection or odontoid peg). When the joints between the base of the skull and first and second vertebrae erode, the odontoid can shift position and stick up into the base of the skull. This migration puts pressure on the brain stem and can lead to serious motor problems, including difficulty maintaining balance, poor coordination and gait (walking) changes.
Subaxial Subluxation
RA can also affect the lower cervical spine. The third most common spinal condition caused by RA is called subaxial subluxation. Joint erosion can cause the lower cervical vertebrae to slip forward, causing the neck to adopt a hunched-over position.
