What is the most useful diagnostic test after a spinal cord injury?

MRI is the Most Useful Diagnostic Test After Spinal Cord Injury

CT scan is the first-line imaging test for suspected spine injury, but MRI is the most useful diagnostic test after spinal cord injury as it provides superior visualization of the spinal cord, soft tissues, and can predict neurological outcomes.

Imaging Algorithm for Spinal Cord Injury

Initial Evaluation

• CT spine without contrast is the gold standard for identifying spine fractures, subluxation, and dislocation requiring immediate stabilization 1, 2
• CT is superior to radiographs for detecting bony injuries with sensitivity approaching 100% 1
• Plain radiographs have largely been supplanted by CT for assessment of traumatic spine injury 1, 2

When to Perform MRI

MRI should be performed in the following scenarios:

• Presence of neurological deficits (most important indication)
• When there is clinical concern for cord compression
• When CT findings don't explain neurological symptoms
• For preoperative planning when surgical intervention is being considered

Why MRI is Most Useful After Spinal Cord Injury

Superior Soft Tissue Visualization

• MRI is complementary to CT, allowing detailed assessment of soft tissues including ligamentous integrity, intervertebral disc injury, and spinal cord injury 1
• MRI detects significantly more lesions than CT in spinal cord trauma patients 3
• MRI can identify spinal cord contusion, edema, hemorrhage, and compression that CT cannot adequately visualize 1

Prognostic Value

MRI can identify three distinct patterns of spinal cord injury that correlate with neurological outcomes 4:

1. Type I: Decreased signal intensity consistent with acute intraspinal hemorrhage (poorest prognosis)
2. Type II: Bright signal intensity consistent with acute cord edema (better prognosis)
3. Type III: Mixed signal of hypointensity centrally and hyperintensity peripherally consistent with contusion (intermediate prognosis)

Surgical Decision Making

• MRI findings can guide surgical interventions by identifying:
  • Disc herniation
  • Epidural hematoma
  • Extent of cord compression
  • Ligamentous injuries requiring stabilization 1
• French guidelines recommend performing spinal MRI as soon as possible when there is a post-traumatic neurological deficit unexplained by CT findings 1

Timing Considerations

• MRI should be performed as soon as possible after injury, especially if surgical intervention is being considered
• Early MRI (within 24 hours) provides the most valuable information for surgical planning 1
• Emergency surgical decompression within 24 hours of neurological deficit improves long-term neurological recovery 1

Contrast vs. Non-Contrast MRI

• Non-contrast MRI is typically sufficient for acute spinal cord injury evaluation 1, 5
• Contrast-enhanced MRI shows no significant advantage over non-contrast MRI for detecting major injuries (hematoma, edema) 5
• Contrast may only be beneficial when severe soft tissue injury is suspected but not detected on non-contrast MRI 5

Common Pitfalls to Avoid

1. Relying solely on CT: While excellent for bony injuries, CT is limited in detecting cord injury and compressive processes 1
2. Delaying MRI: When neurological deficits are present, prompt MRI is essential for optimal management 1
3. Overlooking non-contiguous injuries: Consider imaging the entire spine as 20% of patients have injuries at multiple levels 2
4. Using CT myelography as initial test: There is no evidence supporting CT myelography as the initial imaging test for post-traumatic evaluation 1

MRI remains the gold standard for evaluating spinal cord injury and should be performed promptly in any patient with neurological deficits following trauma to guide treatment decisions and provide prognostic information.