eMedicine Specialties > Neurology > Inflammatory and Demyelinating Diseases

Ankylosing Spondylitis: Differential Diagnoses & Workup

Author: Alan Schaffert, MD, Former Chief of Staff, Department of Medicine, Doctor's Medical Center of Modesto; Clinical Assistant Professor, University of California at Davis
Contributor Information and Disclosures

Updated: Jan 8, 2007

Differential Diagnoses

Cervical Spondylosis: Diagnosis and Management
Spinal Cord Hemorrhage
Spinal Cord Infarction
Spinal Epidural Abscess

Other Problems to Be Considered

Amyloidosis
Cervical disk syndromes
Mechanical back pain
Rheumatoid arthritis
Lumbosacral disk syndromes
Lumbosacral spondylosis
Spinal injury
Back pain

Workup

Laboratory Studies

  • Low-grade anemia of chronic disease may be present.
  • Antinuclear antibody (ANA) and rheumatoid factor (RF) are within reference ranges.
  • Erythrocyte sedimentation rate (ESR) is normal or mildly elevated; it is more likely to be elevated with active inflammation.
  • C-reactive protein may be elevated with increased disease activity but is not a better indicator of inflammation than ESR.
  • Serum alkaline phosphatase may be elevated when active bone remodeling is occurring.
  • HLA-B27 antigen is positive 90-95% of the time but, notably, is not always present. Furthermore, its presence is not sufficient to make the diagnosis. The test is most helpful when diagnosis is not clear.
  • Cerebrospinal fluid (CSF) protein may be elevated mildly during acute exacerbations.

Imaging Studies

  • Plain radiography of the pelvis shows sacroiliitis or fusion of sacroiliac joints.
  • Lumbar spine radiography may show ossification of the anterior longitudinal ligament and fusion of facet joints. The appearance gives rise to the term bamboo spine. With extensive fusion of the spine, a patient may have a poker spine.
  • CT scan will show bony fusions and eroded laminae and spinous processes.
  • MRI may be needed to document atlantoaxial subluxation. MRI may be indicated after trauma to evaluate the spinal cord and to rule out cauda equina syndrome or epidural hematoma.
    • Cauda equina syndrome may be inflammatory or compressive.
    • In inflammatory cauda equina syndrome, the spinal canal is normal to large with CSF diverticula that are best seen on MRI.
  • Plain films or CT scan of the spine may be indicated after trauma to evaluate for bony injury.

Other Tests

  • Occasionally, joint aspiration may be needed to rule out septic arthritis. With ankylosing spondylitis, synovial fluid may reveal a neutrophilic leukocytosis.

More on Ankylosing Spondylitis

Overview: Ankylosing Spondylitis
Differential Diagnoses & Workup: Ankylosing Spondylitis
Treatment & Medication: Ankylosing Spondylitis
Follow-up: Ankylosing Spondylitis
References
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References

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Further Reading

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Keywords

ankylosing spondylitis, Marie-Strümpell arthritis, Bechterew disease, spondyloarthritis, spondyloarthropathy, chronic inflammatory conditions, AS, inflammation of the joints, inflammation of the tendons, inflammation of the ligaments, iritis, uveitis, aortitis, pulmonary fibrosis, amyloidosis, inflammatory bowel disease

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Contributor Information and Disclosures

Author

Alan Schaffert, MD, Former Chief of Staff, Department of Medicine, Doctor's Medical Center of Modesto; Clinical Assistant Professor, University of California at Davis
Alan Schaffert, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, California Medical Association, and National Stroke Association
Disclosure: Nothing to disclose.

Medical Editor

Rodrigo O Kuljis, MD, Esther Lichtenstein Professor of Psychiatry and Neurology, Director, Division of Cognitive and Behavioral Neurology, Department of Neurology, University of Miami School of Medicine
Rodrigo O Kuljis, MD is a member of the following medical societies: American Academy of Neurology and Society for Neuroscience
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Florian P Thomas, MD, MA, PhD, Drmed, Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Associate Program Director, Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University
Florian P Thomas, MD, MA, PhD, Drmed is a member of the following medical societies: American Academy of Neurology, American Paraplegia Society, and National Multiple Sclerosis Society
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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