Overview of Spinal Stenosis
Spinal stenosis happens when the spaces in the spine narrow and create pressure on the spinal cord and nerve roots. The spinal cord is a bundle of nerves that comes out of the base of the brain and runs down the center of the spine. The nerve roots branch out from the cord. The narrowing usually occurs over time and involves one or more areas of the spine:
- The spinal canal, the hollow space in the center of each vertebrae (bones in the spine that protect the spinal cord); the spinal cord and nerve roots run through the spinal canal.
- The space at the base or roots of nerves branching out from the spinal cord.
- The openings between vertebrae, through which nerves leave the spine and go to other parts of the body.
There are many different structures in the anatomy of the back that work together to support your body. There are four regions of the spine:
- Cervical spine.
- Thoracic spine.
- Lumbar spine.
- Sacrum and coccyx.
Spinal stenosis most commonly develops in the lumbar spine and cervical spine.
Who Gets Spinal Stenosis?
Anyone can get spinal stenosis; however, the chances of developing the disorder increase with age. Spinal stenosis also can be present in younger people who are born with a narrow spinal canal or who have an injury to the spine.
Symptoms of Spinal Stenosis
Symptoms of spinal stenosis may develop when the spaces within the spine narrow, most often in the lower back and neck. The narrowing creates pressure on the spine and related structures, causing symptoms. For most people, symptoms develop and progress slowly over a period of time, and some people may not have any symptoms.
The symptoms you experience depend on the location of the narrowing in your spine. Symptoms of spinal stenosis in the lower back can include:
- Pain in the lower back.
- Burning pain or ache that radiates down the buttocks and into the legs, that typically worsens with standing or walking and gets better with leaning forward (flexion).
- Numbness, tingling, or cramping in the legs and feet. These may become more pronounced during standing or walking.
- Weakness in the legs and feet.
Symptoms of spinal stenosis in the neck may include:
- Neck pain.
- Numbness or tingling that radiates down the arms into the hands.
- Weakness in a hand, arm, or fingers.
Walking, standing, or extending the lumbar area of the spine can cause symptoms to worsen. Sitting or flexing the lower back or neck may relieve symptoms. The flexed position “opens up” the spinal column, enlarging the spaces between vertebrae at the back of the spine.
People with more severe stenosis also may have problems with:
- Bowel function.
- Bladder function.
- Sexual function.
Causes of Spinal Stenosis
Several factors can contribute to the narrowing of the spinal canal, leading to spinal stenosis. Normally, the vertebral canal provides enough room for the spinal cord, cauda equina, and the exiting nerves. However, aging and age-related changes in the spine, injury, other diseases, or inherited conditions can cause narrowing of the spaces.
Aging and Age-Related Changes in the Spine
Aging and age-related changes in the spine happen over a period of time and slowly cause loss of the normal structure of the spine. They are the most common causes of spinal stenosis. As people age, the ligaments that keep the vertebrae of the spine in place may thicken and calcify (harden from deposits of calcium salts). Bones and joints may also enlarge. When surfaces of the bone begin to project out from the body, these projections are called osteophytes (bone spurs). For example:
- A herniated (bulging) disk may place pressure on the spinal cord or nerve root. Disks are cushion-like pads that lie between the vertebrae and act like shock absorbers and spacers for the spine. As the disk ages, it can dry out and crack, causing the disk to bulge.
- When a segment of the spine becomes too mobile, the capsules (membranes) of the facet joints at the back of the vertebrae thicken. This effort to try to stabilize the segment can cause bone spurs, which decrease the space around the nerve roots leaving the spinal cord.
- Spondylolisthesis happens when one vertebra slips forward on another vertebra. This creates poor alignment of the spinal column and can place pressure on the spinal cord or nerve roots.
Arthritis is also a common cause of spinal stenosis. Two forms of arthritis that may affect the spine are osteoarthritis and rheumatoid arthritis.
- Osteoarthritis is a degenerative joint disease in which the tissues in the joint break down over time. It is the most common type of arthritis and is more common in older people. Osteoarthritis can lead to disk degeneration and an enlargement or overgrowth of bone that narrows the central and nerve root canals, causing spinal stenosis.
- Rheumatoid Arthritis (RA) is a chronic (long-lasting) inflammatory disease that mostly affects joints. RA causes pain, swelling, stiffness, and loss of function in joints. It is an autoimmune disorder because the immune system attacks the healthy joint tissues. Although not a common cause of spinal stenosis, damage from RA can cause significant problems with joints in the spine, leading to spinal stenosis.
The following conditions also may cause spinal stenosis:
- Tumors of the spine are abnormal growths of soft tissue that may affect the spinal canal directly by causing inflammation or growth of tissue into the spinal canal. This can narrow the space and cause bone changes, leading to spinal stenosis. Some people develop a rare disorder called epidural lipomatosis, which happens when fat builds up on or around the lining of the spine.
- Fractures due to trauma (injury) or other medical conditions may cause misalignment of the spine and the spinal canal or cause fractures that produce fragments of bone that penetrate the canal.
- Paget's disease of bone is a chronic (long-lasting) disorder that causes bones to grow larger and become weaker than normal. As Paget’s disease progresses, new bone forms at a faster rate than the rate at which old bone is removed. However, the new bone does not form correctly, leading to larger bones that are misshapen, weaker, and softer than normal bone. This can cause problems with blood supply and bone structure, which changes the spaces in the spinal canal, leading to spinal stenosis.
- Ossification of the posterior longitudinal ligament happens when calcium deposits form on the ligament that runs up and down behind the spine and inside the spinal canal. These deposits turn the fibrous tissue of the ligament into bone and may press on the nerves in the spinal canal.
Some people are born with a condition that can cause spinal stenosis. These conditions cause the spinal canal to narrow, leading to spinal stenosis. For example:
- Congenital stenosis happens when you are born with a small and narrow spinal canal.
- Scoliosis is a curvature of the spine.
- Achondroplasia is an inherited condition that causes problems with bone formation in the spine and other bones in the body.