WHAT IS RHEUMATOID ARTHRITIS?
Rheumatoid arthritis is a disease that affects all of the synovial joints in the body. A synovial joint,the most common and most movable joint in humans, has a capsule that surrounding the surfaces of the joint and contains a lubricating synovial fluid within the capsules.
There are synovial joints in the spine, thus people with rheumatoid arthritis can have spinal involvement. The destruction caused by the disease process affects different regions of the spine.
Based on the severity of destruction symptoms can range from minimal to serious life-threatening pressure on the spinal cord.
JOINT DESTRUCTION OF THE SPINE
A joint is a connection between two bones. Our spine is made up of multiple joints at each level and many of these joints in the spine are synovial joints.
One is a pivot joint found at the very top of the spine, called the atlanto-axial joint. This joint is between the very first (C1) and second (C2) cervical vertebrae which are very specialized to the spine to allow for rotational movement.
The first cervical vertebra (C1) is called the atlas and is aptly named after the Greek god Altas, who carried the world on his shoulders. This bone is formed like a ring that sits upon the second cervical vertebra (C2).
C2 is called the axis as it is the line upon which the head and C1 rotate upon. The C2 vertebra has a bony knob called the odontoid process that fits in the front part of the C1 ring.
A special ligament holds the odontoid process tightly to the ring of C1. This is the atlanto-axial joint.
In addition to this specialized joint, the skull (occipital) is connected to the cervical spine at C1. Between these bones on each side of the spine are synovial joints called the occipital-cervical joint.
Each spinal motion segment of the spine also has a pair of facet joints that provide the posterior support for the spine. Facet joints are synovial joints. Thus, rheumatoid arthritis may affect the atlanto-axial joint, the occipital-cervical joint, and the facet joints along the spine.
CAUSES OF RHEUMATOID ARTHRITIS
Rheumatoid arthritis is a disease that causes destruction of synovial joints. As the joints are destroyed, the connection between each vertebra becomes unstable.
Serious problems can result when the synovial joints, in particular the atlanto-axial joint, in the neck are destroyed. If stable joints are destroyed, vertebra become unstable and are able to slide forward (listhesis) on top of the adjacent vertebra.
This slippage in the neck is called anterior listhesis and can lead to pressure on the nerve roots and the spinal cord in the neck. This is most dramatic at the atlanto-axial joint (between C1 and C2). If you remember from above, this joint is unique in that it has a knobby odontoid process. There is a risk at this level that instability causes the odontoid to push into the spinal cord which can result in serious problems.
The connection between the skull and the C1 vertebra (occipital-cervical joint) may become unstable allowing the skull to settle down. This can also cause pressure on the spinal cord if the odontoid moves up into the skull through an opening called the foramen magnum. The blood supply to the brain is from two vertebral arteries that also enter the skull through this opening and may be compressed by the odontoid.
RHEUMATOID ARTHRITIS SYMPTOMS
The symptoms of rheumatoid arthritis in the cervical spine are extremely varied. The arthritic changes can cause pain from overall joint inflammation in the synovial joints. This can be felt as dull pain in the back of the neck or at the base of the skull. More concerning rheumatoid arthritis symptoms are noticed if the disease progresses to increase pressure on the spinal cord.
Because the blood supply to the neck can also be affected, any pressure on the vertebral arteries can cause black-outs or dizzy spells if the brain does not get enough oxygen. Increased pressure on the spinal cord may cause many symptoms.
Cord compression may change in the ability to walk. You may notice changes in your gait, or walking style, or have problems with balance. Because the nerves exit our brain and run down, a high cord compression can cause symptoms into the arms or legs such as tingling, weakness, or loss of fine motor skills or coordination. Changes in bowel or bladder control such as incontinence or inability to urinate can also occur.