What is the recommended imaging diagnostic for spinal epidural abscess?

MRI Without and With IV Contrast is the Recommended Imaging Diagnostic for Spinal Epidural Abscess

MRI without and with IV contrast is the recommended imaging diagnostic for spinal epidural abscess due to its excellent sensitivity (96%) and specificity (94%) for detecting spine infections and optimal depiction of the epidural space. 1

Rationale for MRI as First-Line Imaging

MRI provides several critical advantages for diagnosing spinal epidural abscess:

• Superior tissue characterization: MRI offers excellent delineation of soft tissues, allowing visualization of:

  • Epidural fluid collections
  • Spinal cord compression
  • Paraspinal muscle edema (97% sensitivity for SEA) 2
  • Bone marrow edema (65% sensitivity)
  • Abnormal disk signal (66% sensitivity)

• IV contrast enhancement benefits:

  • Helps identify epidural fluid collections
  • Defines size and extent of abscesses
  • Determines presence of spinal cord/cauda equina compression
  • Distinguishes abscess from phlegmon 1
  • Enhances visualization of inflammatory changes

Protocol Specifics

The optimal MRI protocol includes:

• T1-weighted sequences
• T2-weighted sequences with fat suppression or STIR (Short Tau Inversion Recovery)
• Post-contrast T1-weighted sequences with fat suppression

Both pre-contrast and post-contrast images are necessary, as comparing these helps confirm areas of suspected abnormality and evaluate the presence and extent of enhancement 1.

Alternative Imaging Options

When MRI is contraindicated or unavailable:

1. CT with IV contrast: While CT has lower sensitivity (6%) for epidural abscess identification, it may show:

   • Gross spinal cord compression in advanced cases
   • Paraspinal soft tissue abnormalities
   • Osseous changes

2. Plain radiography: Not useful as initial imaging for epidural abscess as it:

   • Is insensitive to epidural space evaluation
   • Cannot detect spinal cord compression
   • May only serve as a complementary test for surgical planning 1

Important Clinical Considerations

• Imaging the entire spine: Consider imaging the entire spine in selected cases as epidural abscesses can occur at noncontiguous sites 3

• Unenhanced MRI findings: When contrast cannot be administered, paraspinal edema is the most sensitive feature (97%) on unenhanced MRI for detecting SEA 2

• Follow-up imaging: Contrast-enhanced MRI is valuable for monitoring response to therapy and can document decrease in abscess size correlating with clinical improvement 4

• Common pitfall: Focusing imaging on only one spinal segment may miss noncontiguous abscesses, which can lead to delayed diagnosis and new neurological deficits 3

In emergent situations with suspected epidural abscess, particularly in patients with risk factors (diabetes, IV drug use, immunosuppression) and elevated ESR, prompt MRI without and with IV contrast should be performed to facilitate early diagnosis and prevent potentially devastating neurological sequelae 1, 5.