Ankylosing Spondylitis (AS), Neurologic Perspective

Low back pain with stiffness is a symptom of ankylosing spondylitis.

Ankylosing spondylitis (AS) is a long-term disease that affects the joints near the center of the body, especially the spine and sacroiliac joints. The sacroiliac joints are located at the lowest end of the spine where the sacrum meets the iliac bone in the pelvis. AS can lead to eventual fusion of the spine. Peripheral joints away from the spine, such as the hips and knees, may also be involved.

AS also frequently involves inflammation at the points where the ligaments and tendons insert into the bones. As it progressively affects the spine, it can cause rigidity of the spine and loss of flexibility. It may also cause pain and stiffness in the hips, knees, and occasionally the small joints of the feet. Inflammation of the connective tissue of the undersurface of the foot (plantar fasciitis) may also occur. Chest wall cartilage inflammation can cause chest pain and tenderness.

Nonskeletal problems associated with AS may include fatigue, inflammation of the iris or uvea (the colored portion of the eye), and less commonly inflammation of the aorta, scarring of the lungs (pulmonary fibrosis), amyloidosis (excess deposition of an abnormal protein in organs and tissues), and inflammatory bowel disease.

AS is more common in males than in females. The male-to-female ratio is approximately 3:1. The peak onset is in adolescents and young adults 15-30 years of age.

The genes we inherit seem to play a major role in the risk for developing AS. Most Caucasian people with AS have the human leukocyte antigen B27 (HLA-B27) antigen, but not everyone who has that antigen develops AS. In a genetically susceptible individual, it is conceivable that infectious agents might stimulate an abnormal immune response, causing the development of AS.

Sacroiliitis. Pelvic X-ray film showing erosion of the sacroiliac joints.

• Low back pain and stiffness gradually increase over three or more months. The pain is usually described as follows:
  • Worse in the morning with improvement during the day
  • Better with activity and worse with inactivity (This finding helps in distinguishing AS from mechanical low back pain.)
  • Gradual ascending pattern from the lumbar region to the thoracic spine and then the cervical spine
  • Improves in response to anti-inflammatory medications
• Some people with AS experience proximal joint (hips, knees) involvement. Rarely, people with AS may complain mostly of small joint (ankles, toes [metatarsophalangeal joints]) involvement. Arm joints are rarely involved.
• People with AS may describe pain and stiffness of the rib cage. Breathlessness on exertion may be experienced. In long-standing diseases, a small percentage of patients may develop fibrosis (scarring) in the upper lobes of the lungs.

• The HLA-B27 antigen (a specific protein on white blood cells) is found in a blood test of most Caucasian people in the U.S. with ankylosing spondylitis. The gene encoding this protein is less frequent in non-Caucasian groups. However, its presence is not sufficient to make the diagnosis. The test for HLA-B27 is most helpful when the diagnosis is not clear.
• Cerebrospinal fluid protein level may be mildly elevated during acute exacerbations of AS.
• Low-grade anemia (decreased hemoglobin level) may be present.
• Plain X-ray films of the pelvis may show sacroiliitis or, later, fusion of sacroiliac joints.
• Spinal X-ray films of the lumbar region may show changes in the ligaments and fusion of facet joints (bony prominences on the vertebrae that form joints with similar projections on the upper or lower aspect of adjacent vertebrae). Extensive fusion leads to the spinal appearance of a "bamboo spine."
• Spinal CT scan or MRI scan may show bony fusions and eroded laminae and spinous processes (parts of the vertebrae).
• Flexion and extension X-ray views of the neck may be needed to document dislocation of the first two cervical vertebrae. MRI may be indicated after trauma to evaluate the spinal cord and to rule out cauda equina syndrome or epidural hematoma (blood in the space between the wall of the spinal canal and the covering of the spinal cord).
  • Cauda equina syndrome may be due to either inflammation or compression. This may occur late in the disease course.
  • In inflammatory cauda equina syndrome, the spinal canal is normal to large with cerebrospinal fluid diverticulae (outpouchings) that are best seen on MRI.
• Plain spinal X-ray films or spinal CT scans may be indicated after trauma to evaluate for bony injury.

General principles of treatment include the following:

• Exercise and postural training to strengthen the back and neck and help maintain correct posture
• Medications to decrease pain and inflammation
• Diagnosis and treatment of potential complications
• Smoking cessation

Good sleeping posture with a small pillow on a firm mattress in either the supine (lying face upward) position or the prone (lying face downward) position helps in alleviating pain and stiffness in people with ankylosing spondylitis. Heat or cold applications can be helpful. Exercise is essential. This includes yoga for flexibility, physical therapy, and aerobic exercise, all of which can help neck pain from the cervical spine, as well as back pain and function.

The goal of drug therapy is to control pain, decrease inflammation, optimize function, and prevent complications. Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used medications. NSAIDs reduce pain and flare-ups of inflammation. No particular NSAID, such as ibuprofen (Advil, Motrin) or naproxen (Aleve, Naprosyn), has been shown to be clearly superior for treating AS. Sulfasalazine (Azulfidine, Azulfidine EN-tabs, Sulfazine) and corticosteroids are also used.

Recently, biologic agents have been found to be particularly useful in treating AS. Proteins now approved to treat AS that block a chemical messenger of inflammation, tumor necrosis factor, include etanercept (Enbrel), adalimumab (Humira), infliximab (Remicade), golimumab (Simponi), and certolizumab (Cimzia). Etanercept, adalimumab, golimumab, and certolizumab are administered as injections. Infliximab is administered as an intravenous infusion. Other biologics for treating adults with ankylosing spondylitis include those that intercept a chemical messenger of inflammation called interleukin 17. An example of one such biologic currently approved for use in adults with ankylosing spondylitis is secukinumab (Cosentyx), which is given by subcutaneous injection. These target the inflammatory disease process directly and may alter the disease course, even causing remission.

For more information, see Understanding Ankylosing Spondylitis Medications.

Neurological complications include C1-C2 subluxation (partial displacement of the first and second cervical vertebrae), a tendency for spinal fractures with minor trauma, spinal stenosis (narrowing) in the cervical (neck) or lumbar (low back) regions, chronic inflammatory cauda equina (compression of the low back nerve roots that causes paralysis and cuts off sensation to the legs), and radiculopathy (shooting pain caused by pressure on the nerves) secondary to fracture or compression of the nerve roots.

Surgical treatment may be necessary for some complications of ankylosing spondylitis.

• Surgical fusion may be required to stabilize a dislocation of the first two cervical vertebrae (atlantoaxial subluxation).
• Cervical spine fractures require rigid immobilization, in such situations, surgical fusion is usually not required.
• Surgery is rarely indicated for correction of uncomplicated thoracic kyphosis (excessive curvature of the upper part of the spine, resulting in hunchback).
• Thoracolumbar fractures require reduction of displacement and stabilization, usually with rods. Laminectomy (a surgery to remove part of the lamina of the vertebral body) is rarely needed.
• Decompression of cervical or lumbar spinal stenosis is performed when nerves are compressed.
• If weight-bearing joints are involved, hip or knee replacement may be necessary.

• Daily bending, twisting, and gentle range of motion exercises help prevent postural deformities and restriction of joint movement and improve the quality of living with AS. Stretching exercises minimize the long-term impact of spinal stiffness and restrictions.
• Breathing exercises are recommended to prevent chest wall immobility. Cessation of smoking is mandatory.

• Symptoms of pain and stiffness are common and may be moderately severe to severe. People with ankylosing spondylitis have few problems with social interactions, although depression is common.
• Most people remain employed, and relatively few develop severe functional disability. Disability correlates with the duration of disease, disease activity, and spinal mobility. Peripheral joint involvement also results in greater impairment.