MRI Lumbar Spine Without IV Contrast
For a patient with lumbosacral pain and numbness following direct trauma to the lumbosacral region, order an MRI lumbar spine without IV contrast 1.
Rationale Based on ACR Guidelines
The 2025 ACR Appropriateness Criteria for acute spinal trauma explicitly addresses this clinical scenario 1. In patients age 16 or older with acute lumbar spine blunt trauma and suspected nerve root or spinal cord injury:
- MRI without contrast is the appropriate next imaging study after initial assessment
- CT alone is insufficient because it cannot detect critical soft tissue pathologies including:
- Nerve root injuries or avulsions
- Spinal cord contusions
- Epidural hematomas
- Disk-ligamentous injuries
- Traumatic disk herniations
IV contrast is not indicated for this clinical presentation 1. The ACR guideline states there is no relevant literature supporting the use of MRI with IV contrast or MRI without and with IV contrast for evaluating suspected ligamentous, spinal cord, or nerve root injury in trauma patients.
Protocol Specifications
Based on current musculoskeletal radiology practice patterns 2, the standard lumbar spine MRI protocol should include:
Sagittal sequences:
- T1-weighted
- T2-weighted
- STIR (Short Tau Inversion Recovery)
Axial sequences:
- T2-weighted imaging (minimum requirement)
- Consider T1-weighted paired with T2-weighted for comprehensive evaluation
This core protocol is used by 77.7% of musculoskeletal radiologists in the United States 2.
Clinical Context for Trauma
MRI is the crucial diagnostic tool for characterizing the cause and extent of spinal cord and nerve root injuries from trauma 1. Key findings that MRI can identify in your patient include:
- Nerve root compression from fracture fragments, hematoma, or disk herniation
- Intramedullary hemorrhage or edema if cord involvement
- Severity of neural compression to guide surgical decision-making
- Conus medullaris injury given the lumbosacral location
The presence of numbness following direct trauma represents a neurological symptom that mandates MRI evaluation beyond CT, even if initial CT appears normal 1.
Important Caveats
Timing considerations: If the patient has cauda equina syndrome features (saddle anesthesia, bowel/bladder dysfunction, bilateral leg weakness), this represents an absolute surgical emergency requiring immediate imaging and "as early as possible" intervention 3.
False-positive awareness: Be aware that MRI has a 25-40% false-positive rate for cervical spine injuries 1, though this data is primarily from cervical studies. Correlate imaging findings with clinical examination to avoid overtreatment of neurologically intact patients.
Sacral fracture specific: If imaging reveals a displaced sacral fracture with nerve compression and progressive neurological deficit, this may require both reduction and laminectomy 3. MRI is essential for identifying nerve root compression in this context.