Stenosis is a term meaning narrowing of a passageway. The nervous system depends on openings in the vertebral column, known as foramen, to be free of obstacles so that nerves can pass through them and serve the various muscles and organs of the body. MayoClinic.com explains that arthritis can cause bone spurs to grow in the spine and other areas of the skeletal system. These bone spurs can impinge on nerves as they pass from the spinal cord to their destination.
Foraminal Stenosis
Neurosurgeon Dr. Charles Ray, an international lecturer and consultant specializing in spinal disorders, describes foraminal stenosis on the website Spine-Health as occurring when an osteophyte, or bone spur, grows from a degenerating intervertebral disc. These cartilaginous discs separate each of the vertebrae, cushioning them and enabling movement between them. Bone spurs from a degenerating disc can grow into the foramen located in the vertebral column, where the spinal nerves exit the spinal cord to become part of the peripheral nervous system. Foraminal stenosis, also known as lateral spinal stenosis, occurs primarily in the lower back, which is supported by the lumbar spine.
Central Stenosis
Ray notes that the central canal of the vertebral column, through which the spinal cord descends, can be narrowed by degenerative arthritis, which erodes the cartilage of the intervertebral discs and causes the proliferation of bone spurs. Degenerating discs can bulge into the central canal, decreasing the amount of space available to the spinal cord. The National Institute of Arthritis and Musculoskeletal and Skin Diseases notes that some people are born with smaller than usual central spinal canals, and conditions such as scoliosis can further impact the diameter of the passageway through which the spinal cord descends.
Far Lateral Stenosis
Beyond the confines of the vertebral column, degenerative bone changes caused by arthritis can produce bone spurs as well as bulging or herniated discs that compress a nerve, according to Ray. This condition is known as far lateral stenosis.
In persons with osteoarthritis, the degeneration that can cause stenosis occurs due to the erosion of cartilage that allows joints to glide smoothly. This cartilage loss is often followed by the growth of bone spurs, impaired joint movement and, in the vertebral column, disc degeneration. Persons with rheumatoid arthritis experience inflammation of the membranes and soft tissues that support the joints, called the synovium. Rheumatoid arthritis does not commonly cause stenosis of the spine, but can disrupt vertebral mobility, most often in the neck.
