Ankylosing Spondylitis, Neurologic Perspective (cont.)
What Tests and Exams Help Diagnose Ankylosing Spondylitis?
- 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.
Medically Reviewed by a Doctor on 9/11/2017
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