Case 8: What scan to order

Clinical History

HPI: 32 year old female with low back pain who now presents with saddle anesthesia.

Questions

1. What is your clinical differential diagnosis?

Answer

2. What scan would you order?

Since the patient is not only presenting with back pain but also focal neurologic deficits, an MRI of the lumbar spine

is indicated. The American College of Radiology (ACR) issues appropriateness criteria for imaging in various

clinical situations. If you are interested in learning more about ACR guidelines on imaging back pain click here.

Indications for Imaging in the Setting of Low Back Pain

Clinical Red Flags

  • When red flags are present.
  • Neurological symptoms present in chronic LBP
  • Following persistent LBP after 4-6 weeks
  • Major trauma, or minor trauma in older or osteoporotic patients
  • Unexplained weight loss
  • Unexplained fever
  • Immunosuppression
  • History of cancer
  • IV drug use
  • Prolonged use of corticosteroids, osteoporosis
  • Age >70
  • Focal neurologic deficit, progressive or disabling symptoms
  • Duration greater than 6 weeks

Why not image everyone?

  • Immediate imaging shown not to improve pain, function or well being when red flags not present.
  • 90% of acute low back pain resolves in 6 weeks.
  • Conclusion:Clinicians should refrain from routine immediate lumbar imaging in patients with low back pain without features suggesting a serious underlying condition.

References:

1. Chou, R., Fu, R., Carrino, J.A., Deyo, R.A. Imaging strategies for low back pain:

Systematic review and meta-analysis. Lancet 2009; 373: 463-72.

2. Humphreys, S.C., Eck, J.C., Hodges, S.D. Neuroimaging in low back pain. American

Family Physician 2002; 65: 2299-2306.