Exams and Tests for Ankylosing Spondylitis
To diagnose ankylosing spondylitis, the doctor will go through a typical diagnostic process that includes exams and tests. He or she will also ask about your general health and family medical history because ankylosing spondylitis can be hereditary. Most likely, the doctor will also order a blood workup to look for the HLA-B27 antigen.
A physical examination for ankylosing spondylitis often includes the following:
- Schober Test: Limited motion in the lumbar spine is symptomatic of AS. The Schober test measures the degree of lumbar forward flexion as the patient bends over as though touching their toes. Progressive loss of spinal motion is correlated with x-ray findings.
- Gaenslen Test: Sacroiliac pain is often found in the early stage of AS. Gaenslen's maneuver, another name for the Gaenslen test, stresses the sacroiliac joints. Increased pain during this maneuver could be indicative of joint disease.
- Chin-Brow Measurement: This is a method used to measure the spine's curve in the neck. Patient with AS often have necks that angle forward sharply as the spine stiffens. If the doctor is going to use the chin-brow measurement to monitor your angle, the first time he or she takes the measurement will be called your "baseline." After that, the doctor will compare each successive chin-brow measurement to the baseline to see if the angle is getting worse.
- Chest Expansion: When ankylosing spondylitis affects the mid-back region (thoracic spine), normal chest expansion may be compromised. The amount of chest expansion is measured from deep expiration to full inspiration. Measurements significantly less than one inch, which is normal chest expansion, could indicate AS.
- Range of Motion: To test how well and far your joints allow you to move, the doctor measures the degree to which you can perform movements of flexion, extension, lateral bending, and spinal rotation. Asymmetry may also be noted.
A neurologic evaluation is mandatory for patients presenting with a spine disorder. The following symptoms are assessed: pain, numbness, paresthesias (e.g., tingling), extremity sensation, motor function, muscle spasm, weakness, and bowel/bladder changes.
Plain radiographs (x-rays) are standard for ankylosing spondylosis. A CT scan or MRI may be ordered to evaluate bone and soft tissues (e.g., the spinal canal) in greater detail. These tests reveal changes in the spine affected by AS. As the doctor studies your images, he or she may be looking for the following signs:
- Characteristic bilateral sacroiliac changes may appear as blurry erosions (wearing away) or hardening/thickening of fibrous tissue (sclerosis) on either side of the joint(s).
- Loss of cartilage spacing in the facet joints, which can fuse and become indistinguishable.
- Natural spinal curvature lost and presentation of abnormal kyphosis (humpback) and/or lordosis (swayback).
- Spinal fractures anywhere in the spinal column. A CT Scan or MRI may detect epidural bleeding common following spinal fracture. This bleeding may cause a semisolid swelling (hematoma), causing compression of neural elements. Fractures may lead to neurologic deficit and/or spinal deformity.
- Lumbar vertebrae may appear abnormally square from erosion that has occurred where bone meets fibrous tissue during the inflammatory phase.
- "Bamboo Spine" is typical of ankylosing spondylitis and results from ossification of the annulus fibrosus (outer portion of the intervertebral disc—the cushion between your vertebrae), the ligament that runs along the front of your spine, and bony bridges that form across the intervertebral spaces. Over time, the spine may start to look like one, long bone; that is Bamboo Spine.